List Pagination for YANG-driven Protocols
draft-ietf-netconf-list-pagination-03
| Document | Type | Active Internet-Draft (netconf WG) | |
|---|---|---|---|
| Authors | Kent Watsen , Qin Wu , Per Andersson , Olof Hagsand , Hongwei Li | ||
| Last updated | 2024-04-18 (Latest revision 2024-03-01) | ||
| Replaces | draft-wwlh-netconf-list-pagination | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Yang Validation | 0 errors, 1 warnings | ||
| Reviews |
YANGDOCTORS Last Call Review due 2024-05-01
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draft-ietf-netconf-list-pagination-03
NETCONF Working Group K. Watsen
Internet-Draft Watsen Networks
Intended status: Standards Track Q. Wu
Expires: 2 September 2024 Huawei Technologies
P. Andersson
Cisco Systems
O. Hagsand
SUNET
H. Li
Hewlett Packard Enterprise
1 March 2024
List Pagination for YANG-driven Protocols
draft-ietf-netconf-list-pagination-03
Abstract
In some circumstances, instances of YANG modeled "list" and "leaf-
list" nodes may contain numerous entries. Retrieval of all the
entries can lead to inefficiencies in the server, the client, and the
network in between.
This document defines a model for list pagination that can be
implemented by YANG-driven management protocols such as NETCONF and
RESTCONF. The model supports paging over optionally filtered and/or
sorted entries. The solution additionally enables servers to
constrain query expressions on some "config false" lists or leaf-
lists.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 2 September 2024.
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Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Adherence to the NMDA . . . . . . . . . . . . . . . . . . 4
2. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 4
3. Solution Details . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Query Parameters for a Targeted List or Leaf-List . . . . 5
3.2. Query Parameter for Descendant Lists and Leaf-Lists . . . 10
3.3. Constraints on "where" and "sort-by" for "config false"
Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3.1. Identifying Constrained "config false" Lists and
Leaf-Lists . . . . . . . . . . . . . . . . . . . . . 11
3.3.2. Indicating the Constraints for "where" Filters and
"sort-by" Expressions . . . . . . . . . . . . . . . . 12
4. The "ietf-list-pagination" Module . . . . . . . . . . . . . . 13
4.1. Data Model Overview . . . . . . . . . . . . . . . . . . . 13
4.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 13
4.2.1. Constraining a "config false" list . . . . . . . . . 13
4.2.2. Indicating number remaining in a limited list . . . . 14
4.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 14
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
5.1. The "IETF XML" Registry . . . . . . . . . . . . . . . . . 23
5.2. The "YANG Module Names" Registry . . . . . . . . . . . . 23
6. Security Considerations . . . . . . . . . . . . . . . . . . . 23
6.1. Considerations for the "ietf-list-pagination" YANG
Module . . . . . . . . . . . . . . . . . . . . . . . . . 23
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
7.1. Normative References . . . . . . . . . . . . . . . . . . 24
7.2. Informative References . . . . . . . . . . . . . . . . . 25
Appendix A. Vector Tests . . . . . . . . . . . . . . . . . . . . 26
A.1. Example YANG Module . . . . . . . . . . . . . . . . . . . 27
A.2. Example Data Set . . . . . . . . . . . . . . . . . . . . 34
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A.3. Example Queries . . . . . . . . . . . . . . . . . . . . . 39
A.3.1. The "limit" Parameter . . . . . . . . . . . . . . . . 39
A.3.2. The "offset" Parameter . . . . . . . . . . . . . . . 42
A.3.3. The "cursor" Parameter . . . . . . . . . . . . . . . 44
A.3.4. The "direction" Parameter . . . . . . . . . . . . . . 49
A.3.5. The "sort-by" Parameter . . . . . . . . . . . . . . . 50
A.3.6. The "where" Parameter . . . . . . . . . . . . . . . . 54
A.3.7. The "locale" Parameter . . . . . . . . . . . . . . . 56
A.3.8. The "sublist-limit" Parameter . . . . . . . . . . . . 58
A.3.9. Combinations of Parameters . . . . . . . . . . . . . 62
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 64
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 64
1. Introduction
YANG modeled "list" and "leaf-list" nodes may contain a large number
of entries. For instance, there may be thousands of entries in the
configuration for network interfaces or access control lists. And
time-driven logging mechanisms, such as an audit log or a traffic
log, can contain millions of entries.
Retrieval of all the entries can lead to inefficiencies in the
server, the client, and the network in between. For instance,
consider the following:
* A client may need to filter and/or sort list entries in order to,
e.g., present the view requested by a user.
* A server may need to iterate over many more list entries than
needed by a client.
* A network may need to convey more data than needed by a client.
Optimal global resource utilization is obtained when clients are able
to cherry-pick just that which is needed to support the application-
level business logic.
This document defines a generic model for list pagination that can be
implemented by YANG-driven management protocols such as NETCONF
[RFC6241] and RESTCONF [RFC8040]. Details for how such protocols are
updated are outside the scope of this document.
The model presented in this document supports paging over optionally
filtered and/or sorted entries. Server-side filtering and sorting is
ideal as servers can leverage indexes maintained by a backend storage
layer to accelerate queries.
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1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The following terms are defined in [RFC7950] and are not redefined
here: client, data model, data tree, feature, extension, module,
leaf, leaf-list, and server.
1.2. Conventions
Various examples in this document use "BASE64VALUE=" as a placeholder
value for binary data that has been base64 encoded (per Section 9.8
of [RFC7950]). This placeholder value is used because real base64
encoded structures are often many lines long and hence distracting to
the example being presented.
1.3. Adherence to the NMDA
This document is compliant with the Network Management Datastore
Architecture (NMDA) [RFC8342]. The "ietf-list-pagination" module
only defines a YANG extension and augments a couple leafs into a
"config false" node defined by the "ietf-system-capabilities" module.
2. Solution Overview
The solution presented in this document broadly entails a client
sending a query to a server targeting a specific list or leaf-list
including optional parameters guiding which entries should be
returned.
A secondary aspect of this solution entails a client sending a query
parameter to a server guiding how descendent lists and leaf-lists
should be returned. This parameter may be used on any target node,
not just "list" and "leaf-list" nodes.
Clients detect a server's support for list pagination via an entry
for the "ietf-list-pagination" module (defined in Section 4) in the
server's YANG Library [RFC8525] response.
Relying on client-provided query parameters ensures servers remain
backward compatible with legacy clients.
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3. Solution Details
This section is composed of the following subsections:
* Section 3.1 defines five query parameters clients may use to page
through the entries of a single list or leaf-list in a data tree.
* Section 3.2 defines one query parameter that clients may use to
affect the content returned for descendant lists and leaf-lists.
* Section 3.3 defines per schema-node tags enabling servers to
indicate which "config false" lists are constrained and how they
may be interacted with.
3.1. Query Parameters for a Targeted List or Leaf-List
The five query parameters presented this section are listed in
processing order. This processing order is logical, efficient, and
matches the processing order implemented by database systems, such as
SQL.
The order is as follows: a server first processes the "where"
parameter (see Section 3.1.1), then the "sort-by" parameter (see
Section 3.1.2), then the "direction" parameter (see Section 3.1.4),
and either a combination of the "offset" parameter (see
Section 3.1.5) or the "cursor" parameter (see Section 3.1.6), and
lastly "the "limit" parameter (see Section 3.1.7).
The sorting can furthermore be configured with a locale for
collation. This is done by setting the "locale" parameter (see
Section 3.1.3).
3.1.1. The "where" Query Parameter
Description
The "where" query parameter specifies a filter expression that
result-set entries must match.
Default Value
If this query parameter is unspecified, then no entries are
filtered from the working result-set.
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Allowed Values
The allowed values are XPath 1.0 expressions. It is an error if
the XPath expression references a node identifier that does not
exist in the schema, is optional or conditional in the schema or,
for constrained "config false" lists and leaf-lists (see
Section 3.3), if the node identifier does not point to a node
having the "indexed" extension statement applied to it (see
Section 3.3.2).
Conformance
The "where" query parameter MUST be supported for all "config
true" lists and leaf-lists and SHOULD be supported for "config
false" lists and leaf-lists. Servers MAY disable the support for
some or all "config false" lists and leaf-lists as described in
Section 3.3.2.
3.1.2. The "sort-by" Query Parameter
Description
The "sort-by" query parameter indicates the node in the working
result-set (i.e., after the "where" parameter has been applied)
that entries should be sorted by. Sorts are in ascending order
(e.g., '1' before '9', 'a' before 'z', etc.). Missing values are
sorted to the end (e.g., after all nodes having values). Sub-
sorts are not supported.
Default Value
If this query parameter is unspecified, then the list or leaf-
list's default order is used, per the YANG "ordered-by" statement
(see Section 7.7.7 of [RFC7950]).
Allowed Values
The allowed values are node identifiers. It is an error if the
specified node identifier does not exist in the schema, is
optional or conditional in the schema or, for constrained "config
false" lists and leaf-lists (see Section 3.3), if the node
identifier does not point to a node having the "indexed" extension
statement applied to it (see Section 3.3.2).
Conformance
The "sort-by" query parameter MUST be supported for all "config
true" lists and leaf-lists and SHOULD be supported for "config
false" lists and leaf-lists. Servers MAY disable the support for
some or all "config false" lists and leaf-lists as described in
Section 3.3.2.
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3.1.3. The "locale" Query Parameter
Description
The "locale" query parameter indicates what locale is used when
collating the result-set.
Default Value
If this query parameter is unspecified, it is up to the server
select a locale for collation. How the server chooses the locale
used is out of scope for this document. The result-set includes
the locale used by the server for collation with a metadata value
[RFC7952] called "locale".
Allowed Values
The format is a free form string but SHOULD follow the language
sub-tag format defined in [RFC5646]. An example is 'sv_SE'. If a
supplied locale is unknown to the server, the "locale-unavailable"
SHOULD be produced in the error-app-tag in the error output. Note
that all locales are assumed to be UTF-8, since character encoding
for YANG strings and all known YANG modelled encodings and
protocols are required to be UTF-8 [RFC6241] [RFC7950] [RFC7951]
[RFC8040]. A server MUST accept a known encoding with or without
trailing ".UTF-8" and MAY emit an encoding with or without
trailing ".UTF-8". This means a server must handle both e.g.
"sv_SE" and "sv_SE.UTF-8" equally as output, and chooses how to
emit used locale as output.
Conformance
The "locale" query parameter MUST be supported for all "config
true" lists and leaf-lists and SHOULD be supported for "config
false" lists and leaf-lists. Servers MAY disable the support for
some or all "config false" lists and leaf-lists as described in
Section 3.3.2.
3.1.4. The "direction" Query Parameter
Description
The "direction" query parameter indicates how the entries in the
working result-set (i.e., after the "sort-by" parameter has been
applied) should be traversed.
Default Value
If this query parameter is unspecified, the default value is
"forwards".
Allowed Values
The allowed values are:
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forwards
Return entries in the forwards direction. Also known as the
"default" or "ascending" direction.
backwards
Return entries in the backwards direction. Also known as the
"reverse" or "descending" direction
Conformance
The "direction" query parameter MUST be supported for all lists
and leaf-lists.
3.1.5. The "offset" Query Parameter
Description
The "offset" query parameter indicates the number of entries in
the working result-set (i.e., after the "direction" parameter has
been applied) that should be skipped over when preparing the
response.
Default Value
If this query parameter is unspecified, then no entries in the
result-set are skipped, same as when the offset value '0' is
specified.
Allowed Values
The allowed values are unsigned integers. It is an error for the
offset value to exceed the number of entries in the working
result-set, and the "offset-out-of-range" identity SHOULD be
produced in the error-app-tag in the error output when this
occurs.
Conformance
The "offset" query parameter MUST be supported for all lists and
leaf-lists.
3.1.6. The "cursor" Query Parameter
Description
The "cursor" query parameter indicates where to start the working
result-set (i.e., after the "direction" parameter has been
applied), the elements before the cursor are skipped over when
preparing the response. Furthermore, a result set constrained
with the "limit" query parameter includes metadata values
[RFC7952] called "next" and "previous", which contains cursor
values to the next and previous result-sets. These next and
previous cursor values are opaque index values for the underlying
system's database, e.g. a key or other information needed to
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efficiently access the selected result-set. These "next" and
"previous" metadata values work as Hypermedia as the Engine of
Application State (HATEOAS) links [REST-Dissertation]. This means
that the server does not keep any stateful information about the
"next" and "previous" cursor or the current page. Due to their
ephemeral nature, cursor values are never cached.
Default Value
If this query parameter is unspecified, then no entries in the
result-set are skipped.
Allowed Values
The allowed values are base64 encoded positions interpreted by the
server to index an element in the list, e.g. a list key or other
information to efficiently access the selected result-set. It is
an error to supply an unkown cursor for the working result-set,
and the "cursor-not-found" identity SHOULD be produced in the
error-app-tag in the error output when this occurs.
Conformance
The "cursor" query parameter MUST be supported for all "config
true" lists and SHOULD be supported for all "config false" lists.
It is however optional to support the "cursor" query parameter for
"config false" lists and the support must be signaled by the
server per list.
Servers indicate that they support the "cursor" query parameter
for a "config false" list node by having the "cursor-supported"
extension statement applied to it in the "per-node-capabilities"
node in the "ietf-system-capabilities" model.
Since leaf-lists might not have any unique values that can be
indexed, the "cursor" query parameter is not relevant for the
leaf-lists. Consider the following leaf-list [1,1,2,3,5], which
contains elements without uniquely indexable values. It would be
possible to use the position, but then the solution would be equal
to using the "offset" query parameter.
3.1.7. The "limit" Query Parameter
Description
The "limit" query parameter limits the number of entries returned
from the working result-set (i.e., after the "offset" parameter
has been applied). Any list or leaf-list that is limited
includes, somewhere in its encoding, a metadata value [RFC7952]
called "remaining", a positive integer indicating the number of
elements that were not included in the result-set by the "limit"
operation, or the value "unknown" in case, e.g., the server
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determines that counting would be prohibitively expensive.
Default Value
If this query parameter is unspecified, the number of entries that
may be returned is unbounded.
Allowed Values
The allowed values are positive integers.
Conformance
The "limit" query parameter MUST be supported for all lists and
leaf-lists.
3.2. Query Parameter for Descendant Lists and Leaf-Lists
Whilst this document primarily regards pagination for a list or leaf-
list, it begs the question for how descendant lists and leaf-lists
should be handled, which is addressed by the "sublist-limit" query
parameter described in this section.
3.2.1. The "sublist-limit" Query Parameter
Description
The "sublist-limit" parameter limits the number of entries
returned for descendent lists and leaf-lists.
Any descendent list or leaf-list limited by the "sublist-limit"
parameter includes, somewhere in its encoding, a metadata value
[RFC7952] called "remaining", a positive integer indicating the
number of elements that were not included by the "sublist-limit"
parameter, or the value "unknown" in case, e.g., the server
determines that counting would be prohibitively expensive.
When used on a list node, it only affects the list's descendant
nodes, not the list itself, which is only affected by the
parameters presented in Section 3.1.
Default Value
If this query parameter is unspecified, the number of entries that
may be returned for descendent lists and leaf-lists is unbounded.
Allowed Values
The allowed values are positive integers.
Conformance
The "sublist-limit" query parameter MUST be supported for all
conventional nodes, including a datastore's top-level node (i.e.,
'/').
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3.3. Constraints on "where" and "sort-by" for "config false" Lists
Some "config false" lists and leaf-lists may contain an enormous
number of entries. For instance, a time-driven logging mechanism,
such as an audit log or a traffic log, can contain millions of
entries.
In such cases, "where" and "sort-by" expressions will not perform
well if the server must bring each entry into memory in order to
process it.
The server's best option is to leverage query-optimizing features
(e.g., indexes) built into the backend database holding the dataset.
However, arbitrary "where" expressions and "sort-by" node identifiers
into syntax supported by the backend database and/or query-optimizers
may prove challenging, if not impossible, to implement.
Thusly this section introduces mechanisms whereby a server can:
1. Identify which "config false" lists and leaf-lists are
constrained.
2. Identify what node-identifiers and expressions are allowed for
the constrained lists and leaf-lists.
| Note: The pagination performance for "config true" lists and
| leaf-lists is not considered as already servers must be able to
| process them as configuration. Whilst some "config true' lists
| and leaf-lists may contain thousands of entries, they are well
| within the capability of server-side processing.
3.3.1. Identifying Constrained "config false" Lists and Leaf-Lists
Identification of which lists and leaf-lists are constrained occurs
in the schema tree, not the data tree. However, as server abilities
vary, it is not possible to define constraints in YANG modules
defining generic data models.
In order to enable servers to identify which lists and leaf-lists are
constrained, the solution presented in this document augments the
data model defined by the "ietf-system-capabilities" module presented
in [RFC9196].
Specifically, the "ietf-list-pagination" module (see Section 4)
augments an empty leaf node called "constrained" into the "per-node-
capabilities" node defined in the "ietf-system-capabilities" module.
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The "constrained" leaf MAY be specified for any "config false" list
or leaf-list.
When a list or leaf-list is constrained:
* All parts of XPath 1.0 expressions are disabled unless explicitly
enabled by Section 3.3.2.
* Node-identifiers used in "where" expressions and "sort-by" filters
MUST have the "indexed" leaf applied to it (see Section 3.3.2).
* For lists only, node-identifiers used in "where" expressions and
"sort-by" filters MUST NOT descend past any descendent lists.
This ensures that only indexes relative to the targeted list are
used. Further constraints on node identifiers MAY be applied in
Section 3.3.2.
3.3.2. Indicating the Constraints for "where" Filters and "sort-by"
Expressions
This section identifies how constraints for "where" filters and
"sort-by" expressions are specified. These constraints are valid
only if the "constrained" leaf described in the previous section
Section 3.3.1 has been set on the immediate ancestor "list" node or,
for "leaf-list" nodes, on itself.
3.3.2.1. Indicating Filterable/Sortable Nodes
For "where" filters, an unconstrained XPath expressions may use any
node in comparisons. However, efficient mappings to backend
databases may support only a subset of the nodes.
Similarly, for "sort-by" expressions, efficient sorts may only
support a subset of the nodes.
In order to enable servers to identify which nodes may be used in
comparisons (for both "where" and "sort-by" expressions), the "ietf-
list-pagination" module (see Section 4) augments an empty leaf node
called "indexed" into the "per-node-capabilities" node defined in the
"ietf-system-capabilities" module (see [RFC9196]).
When a "list" or "leaf-list" node has the "constrained" leaf, only
nodes having the "indexed" node may be used in "where" and/or "sort-
by" expressions. If no nodes have the "indexed" leaf, when the
"constrained" leaf is present, then "where" and "sort-by" expressions
are disabled for that list or leaf-list.
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4. The "ietf-list-pagination" Module
The "ietf-list-pagination" module is used by servers to indicate that
they support pagination on YANG "list" and "leaf-list" nodes, and to
provide an ability to indicate which "config false" list and/or
"leaf-list" nodes are constrained and, if so, which nodes may be used
in "where" and "sort-by" expressions.
4.1. Data Model Overview
The following tree diagram [RFC8340] illustrates the "ietf-list-
pagination" module:
module: ietf-list-pagination
augment /sysc:system-capabilities/sysc:datastore-capabilities
/sysc:per-node-capabilities:
+--ro constrained? empty
+--ro indexed? empty
+--ro cursor-supported? empty
Comments:
* As shown, this module augments three optional leafs into the "per-
node-capabilities" node of the "ietf-system-capabilities" module.
* Not shown is that the module also defines an "md:annotation"
statement named "remaining". This annotation may be present in a
server's response to a client request containing either the
"limit" (Section 3.1.7) or "sublist-limit" parameters
(Appendix A.3.8).
4.2. Example Usage
4.2.1. Constraining a "config false" list
The following example illustrates the "ietf-list-pagination" module's
augmentations of the "system-capabilities" data tree. This example
assumes the "example-social" module defined in the Appendix A.1 is
implemented.
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=============== NOTE: '\' line wrapping per RFC 8792 ================
<system-capabilities
xmlns="urn:ietf:params:xml:ns:yang:ietf-system-capabilities"
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"
xmlns:es="https://example.com/ns/example-social"
xmlns:lpg="urn:ietf:params:xml:ns:yang:ietf-list-pagination">
<datastore-capabilities>
<datastore>ds:operational</datastore>
<per-node-capabilities>
<node-selector>/es:audit-logs/es:audit-log</node-selector>
<lpg:constrained/>
</per-node-capabilities>
<per-node-capabilities>
<node-selector>/es:audit-logs/es:audit-log/es:timestamp</node-\
selector>
<lpg:indexed/>
</per-node-capabilities>
<per-node-capabilities>
<node-selector>/es:audit-logs/es:audit-log/es:member-id</node-\
selector>
<lpg:indexed/>
</per-node-capabilities>
<per-node-capabilities>
<node-selector>/es:audit-logs/es:audit-log/es:outcome</node-se\
lector>
<lpg:indexed/>
</per-node-capabilities>
</datastore-capabilities>
</system-capabilities>
4.2.2. Indicating number remaining in a limited list
FIXME: valid syntax for 'where'?
4.3. YANG Module
This YANG module has normative references to [RFC7952] and [RFC9196].
<CODE BEGINS> file "ietf-list-pagination@2024-03-01.yang"
module ietf-list-pagination {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-list-pagination";
prefix lpg;
import ietf-datastores {
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prefix ds;
reference
"RFC 8342: Network Management Datastore Architecture (NMDA)";
}
import ietf-yang-types {
prefix yang;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-yang-metadata {
prefix md;
reference
"RFC 7952: Defining and Using Metadata with YANG";
}
import ietf-system-capabilities {
prefix sysc;
reference
"RFC 9196: YANG Modules Describing Capabilities for Systems and
Datastore Update Notifications";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: https://datatracker.ietf.org/wg/netconf
WG List: NETCONF WG list <mailto:netconf@ietf.org>";
description
"This module is used by servers to 1) indicate they support
pagination on 'list' and 'leaf-list' resources, 2) define a
grouping for each list-pagination parameter, and 3) indicate
which 'config false' lists have constrained 'where' and
'sort-by' parameters and how they may be used, if at all.
Copyright (c) 2024 IETF Trust and the persons identified
as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with
or without modification, is permitted pursuant to, and
subject to the license terms contained in, the Revised
BSD License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info).
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This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC
itself for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
are to be interpreted as described in BCP 14 (RFC 2119)
(RFC 8174) when, and only when, they appear in all
capitals, as shown here.";
revision 2024-03-01 {
description
"Initial revision.";
reference
"RFC XXXX: List Pagination for YANG-driven Protocols";
}
// Annotations
md:annotation remaining {
type union {
type uint32;
type enumeration {
enum "unknown" {
description
"Indicates that number of remaining entries is unknown
to the server in case, e.g., the server has determined
that counting would be prohibitively expensive.";
}
}
}
description
"This annotation contains the number of elements not included
in the result set (a positive value) due to a 'limit' or
'sublist-limit' operation. If no elements were removed,
this annotation MUST NOT appear. The minimum value (0),
which never occurs in normal operation, is reserved to
represent 'unknown'. The maximum value (2^32-1) is
reserved to represent any value greater than or equal
to 2^32-1 elements.";
}
md:annotation next {
type string;
description
"This annotation contains the base64 encoded value of the next
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cursor in the pagination.";
}
md:annotation previous {
type string;
description
"This annotation contains the base64 encoded value of the
previous cursor in the pagination.";
}
md:annotation locale {
type string;
description
"This annotation contains the locale used when sorting.
The format is a free form string but SHOULD follow the
language sub-tag format defined in RFC 5646.
An example is 'sv_SE'.
For further details see references:
RFC 5646: Tags for identifying Languages
RFC 6365: Technology Used in Internationalization in the
IETF";
}
// Identities
identity list-pagination-error {
description
"Base identity for list-pagination errors.";
}
identity offset-out-of-range {
base list-pagination-error;
description
"The 'offset' query parameter value is greater than the number
of instances in the target list or leaf-list resource.";
}
identity cursor-not-found {
base list-pagination-error;
description
"The 'cursor' query parameter value is unknown for the target
list.";
}
identity locale-unavailable {
base list-pagination-error;
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description
"The 'locale' query parameter input is not a valid
locale or the locale is not available on the system.";
}
// Groupings
grouping where-param-grouping {
description
"This grouping may be used by protocol-specific YANG modules
to define a protocol-specific query parameter.";
leaf where {
type union {
type yang:xpath1.0;
type enumeration {
enum "unfiltered" {
description
"Indicates that no entries are to be filtered
from the working result-set.";
}
}
}
default "unfiltered";
description
"The 'where' parameter specifies a boolean expression
that result-set entries must match.
It is an error if the XPath expression references a node
identifier that does not exist in the schema, is optional
or conditional in the schema or, for constrained 'config
false' lists and leaf-lists, if the node identifier does
not point to a node having the 'indexed' extension
statement applied to it (see RFC XXXX).";
}
}
grouping locale-param-grouping {
description
"The grouping may be used by protocol-specific YANG modules
to define a protocol-specific query parameter.";
leaf locale {
type string;
description
"The 'locale' parameter indicates the locale which the
entries in the working result-set should be collated.";
}
}
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grouping sort-by-param-grouping {
description
"This grouping may be used by protocol-specific YANG modules
to define a protocol-specific query parameter.";
leaf sort-by {
type union {
type string {
// An RFC 7950 'descendant-schema-nodeid'.
pattern '([0-9a-fA-F]*:)?[0-9a-fA-F]*'
+ '(/([0-9a-fA-F]*:)?[0-9a-fA-F]*)*';
}
type enumeration {
enum "none" {
description
"Indicates that the list or leaf-list's default
order is to be used, per the YANG 'ordered-by'
statement.";
}
}
}
default "none";
description
"The 'sort-by' parameter indicates the node in the
working result-set (i.e., after the 'where' parameter
has been applied) that entries should be sorted by.
Sorts are in ascending order (e.g., '1' before '9',
'a' before 'z', etc.). Missing values are sorted to
the end (e.g., after all nodes having values).";
}
}
grouping direction-param-grouping {
description
"This grouping may be used by protocol-specific YANG modules
to define a protocol-specific query parameter.";
leaf direction {
type enumeration {
enum forwards {
description
"Indicates that entries should be traversed from
the first to last item in the working result set.";
}
enum backwards {
description
"Indicates that entries should be traversed from
the last to first item in the working result set.";
}
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}
default "forwards";
description
"The 'direction' parameter indicates how the entries in the
working result-set (i.e., after the 'sort-by' parameter
has been applied) should be traversed.";
}
}
grouping cursor-param-grouping {
description
"This grouping may be used by protocol-specific YANG modules
to define a protocol-specific query parameter.";
leaf cursor {
type string;
description
"The 'cursor' parameter indicates where to start the working
result-set (i.e. after the 'direction' parameter has been
applied), the elements before the cursor are skipped over
when preparing the response. Furthermare the result-set is
annotated with attributes for the next and previous cursors
following a result-set constrained with the 'limit' query
parameter.";
}
}
grouping offset-param-grouping {
description
"This grouping may be used by protocol-specific YANG modules
to define a protocol-specific query parameter.";
leaf offset {
type uint32;
default 0;
description
"The 'offset' parameter indicates the number of entries
in the working result-set (i.e., after the 'direction'
parameter has been applied) that should be skipped over
when preparing the response.";
}
}
grouping limit-param-grouping {
description
"This grouping may be used by protocol-specific YANG modules
to define a protocol-specific query parameter.";
leaf limit {
type union {
type uint32 {
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range "1..max";
}
type enumeration {
enum "unbounded" {
description
"Indicates that the number of entries that may be
returned is unbounded.";
}
}
}
default "unbounded";
description
"The 'limit' parameter limits the number of entries returned
from the working result-set (i.e., after the 'offset'
parameter has been applied).
Any result-set that is limited includes, somewhere in its
encoding, the metadata value 'remaining' to indicate the
number entries not included in the result set.";
}
}
grouping sublist-limit-param-grouping {
description
"This grouping may be used by protocol-specific YANG modules
to define a protocol-specific query parameter.";
leaf sublist-limit {
type union {
type uint32 {
range "1..max";
}
type enumeration {
enum "unbounded" {
description
"Indicates that the number of entries that may be
returned is unbounded.";
}
}
}
default "unbounded";
description
"The 'sublist-limit' parameter limits the number of entries
for descendent lists and leaf-lists.
Any result-set that is limited includes, somewhere in
its encoding, the metadata value 'remaining' to indicate
the number entries not included in the result set.";
}
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}
// Protocol-accessible nodes
augment
"/sysc:system-capabilities/sysc:datastore-capabilities"
+ "/sysc:per-node-capabilities" {
// Ensure the following nodes are only used for the
// <operational> datastore.
when "/sysc:system-capabilities/sysc:datastore-capabilities"
+ "/sysc:datastore = 'ds:operational'";
description
"Defines some leafs that MAY be used by the server to
describe constraints imposed of the 'where' filters and
'sort-by' parameters used in list pagination queries.";
leaf constrained {
type empty;
description
"Indicates that 'where' filters and 'sort-by' parameters
on the targeted 'config false' list node are constrained.
If a list is not 'constrained', then full XPath 1.0
expressions may be used in 'where' filters and all node
identifiers are usable by 'sort-by'.";
}
leaf indexed {
type empty;
description
"Indicates that the targeted descendent node of a
'constrained' list (see the 'constrained' leaf) may be
used in 'where' filters and/or 'sort-by' parameters.
If a descendent node of a 'constrained' list is not
'indexed', then it MUST NOT be used in 'where' filters
or 'sort-by' parameters.";
}
leaf cursor-supported {
type empty;
description
"Indicates that the targeted list node supports the
'cursor' parameter.";
}
}
}
<CODE ENDS>
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5. IANA Considerations
5.1. The "IETF XML" Registry
This document registers one URI in the "ns" subregistry of the IETF
XML Registry [RFC3688] maintained at
https://www.iana.org/assignments/xml-registry/xml-registry.xhtml#ns.
Following the format in [RFC3688], the following registration is
requested:
URI: urn:ietf:params:xml:ns:yang:ietf-list-pagination
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
5.2. The "YANG Module Names" Registry
This document registers one YANG module in the YANG Module Names
registry [RFC6020] maintained at https://www.iana.org/assignments/
yang-parameters/yang-parameters.xhtml. Following the format defined
in [RFC6020], the below registration is requested:
name: ietf-list-pagination
namespace: urn:ietf:params:xml:ns:yang:ietf-list-pagination
prefix: lpg
RFC: XXXX
6. Security Considerations
6.1. Considerations for the "ietf-list-pagination" YANG Module
This section follows the template defined in Section 3.7.1 of
[RFC8407].
The YANG module specified in this document defines a schema for data
that is designed to be accessed via network management protocols such
as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer
is the secure transport layer, and the mandatory-to-implement secure
transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer
is HTTPS, and the mandatory-to-implement secure transport is TLS
[RFC8446].
The Network Configuration Access Control Model (NACM) [RFC8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.
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All protocol-accessible data nodes in this module are read-only and
cannot be modified. Access control may be configured to avoid
exposing any read-only data that is defined by the augmenting module
documentation as being security sensitive.
Since this module also defines groupings, these considerations are
primarily for the designers of other modules that use these
groupings.
None of the readable data nodes defined in this YANG module are
considered sensitive or vulnerable in network environments. The NACM
"default-deny-all" extension has not been set for any data nodes
defined in this module.
This module does not define any RPCs or actions or notifications, and
thus the security consideration for such is not provided here.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC5646] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
September 2009, <https://www.rfc-editor.org/info/rfc5646>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
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[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<https://www.rfc-editor.org/info/rfc7951>.
[RFC7952] Lhotka, L., "Defining and Using Metadata with YANG",
RFC 7952, DOI 10.17487/RFC7952, August 2016,
<https://www.rfc-editor.org/info/rfc7952>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of
Documents Containing YANG Data Models", BCP 216, RFC 8407,
DOI 10.17487/RFC8407, October 2018,
<https://www.rfc-editor.org/info/rfc8407>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC9196] Lengyel, B., Clemm, A., and B. Claise, "YANG Modules
Describing Capabilities for Systems and Datastore Update
Notifications", RFC 9196, DOI 10.17487/RFC9196, February
2022, <https://www.rfc-editor.org/info/rfc9196>.
7.2. Informative References
[I-D.ietf-netconf-list-pagination-nc]
Watsen, K., Wu, Q., Hagsand, O., Li, H., and P. Andersson,
"NETCONF Extensions to Support List Pagination", Work in
Progress, Internet-Draft, draft-ietf-netconf-list-
pagination-nc-02, 22 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
list-pagination-nc-02>.
[I-D.ietf-netconf-list-pagination-rc]
Watsen, K., Wu, Q., Hagsand, O., Li, H., and P. Andersson,
"RESTCONF Extensions to Support List Pagination", Work in
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Progress, Internet-Draft, draft-ietf-netconf-list-
pagination-rc-02, 22 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
list-pagination-rc-02>.
[I-D.ietf-netconf-restconf-collection]
Bierman, A., Björklund, M., and K. Watsen, "RESTCONF
Collection Resource", Work in Progress, Internet-Draft,
draft-ietf-netconf-restconf-collection-00, 30 January
2015, <https://datatracker.ietf.org/doc/html/draft-ietf-
netconf-restconf-collection-00>.
[REST-Dissertation]
Fielding, R., "Architectural Styles and the Design of
Network-based Software Architectures", 2000,
<http://www.ics.uci.edu/~fielding/pubs/dissertation/
top.htm>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
Internationalization in the IETF", BCP 166, RFC 6365,
DOI 10.17487/RFC6365, September 2011,
<https://www.rfc-editor.org/info/rfc6365>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
and R. Wilton, "YANG Library", RFC 8525,
DOI 10.17487/RFC8525, March 2019,
<https://www.rfc-editor.org/info/rfc8525>.
Appendix A. Vector Tests
This normative appendix section illustrates every notable edge
condition conceived during this document's production.
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Test inputs and outputs are provided in a manner that is both generic
and concise.
Management protocol specific documents need only reproduce as many of
these tests as necessary to convey pecularities presented by the
protocol.
Implementations are RECOMMENDED to implement the tests presented in
this document, in addition to any tests that may be presented in
protocol specific documents.
A.1. Example YANG Module
The vector tests assume the "example-social" YANG module defined in
this section.
This module has been specially crafted to cover every notable edge
condition, especially with regards to the types of the data nodes.
Following is the tree diagram [RFC8340] for the "example-social"
module:
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module: example-social
+--rw members
| +--rw member* [member-id]
| +--rw member-id string
| +--rw email-address inet:email-address
| +--rw password ianach:crypt-hash
| +--rw avatar? binary
| +--rw tagline? string
| +--rw privacy-settings
| | +--rw hide-network? boolean
| | +--rw post-visibility? enumeration
| +--rw following* -> /members/member/member-id
| +--rw posts
| | +--rw post* [timestamp]
| | +--rw timestamp yang:date-and-time
| | +--rw title? string
| | +--rw body string
| +--rw favorites
| | +--rw uint8-numbers* uint8
| | +--rw uint64-numbers* uint64
| | +--rw int8-numbers* int8
| | +--rw int64-numbers* int64
| | +--rw decimal64-numbers* decimal64
| | +--rw bits* bits
| +--ro stats
| +--ro joined yang:date-and-time
| +--ro membership-level enumeration
| +--ro last-activity? yang:date-and-time
+--ro audit-logs
+--ro audit-log* []
+--ro timestamp yang:date-and-time
+--ro member-id string
+--ro source-ip inet:ip-address
+--ro request string
+--ro outcome boolean
Following is the YANG [RFC7950] for the "example-social" module:
module example-social {
yang-version 1.1;
namespace "https://example.com/ns/example-social";
prefix es;
import ietf-yang-types {
prefix yang;
reference
"RFC 6991: Common YANG Data Types";
}
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import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types";
}
import iana-crypt-hash {
prefix ianach;
reference
"RFC 7317: A YANG Data Model for System Management";
}
organization "Example, Inc.";
contact "support@example.com";
description "Example Social Data Model.";
revision YYYY-MM-DD {
description
"Initial version.";
reference
"RFC XXXX: Example social module.";
}
container members {
description
"Container for list of members.";
list member {
key "member-id";
description
"List of members.";
leaf member-id {
type string {
length "1..80";
pattern '.*[\n].*' {
modifier invert-match;
}
}
description
"The member's identifier.";
}
leaf email-address {
type inet:email-address;
mandatory true;
description
"The member's email address.";
}
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leaf password {
type ianach:crypt-hash;
mandatory true;
description
"The member's hashed-password.";
}
leaf avatar {
type binary;
description
"An binary image file.";
}
leaf tagline {
type string {
length "1..80";
pattern '.*[\n].*' {
modifier invert-match;
}
}
description
"The member's tagline.";
}
container privacy-settings {
leaf hide-network {
type boolean;
description
"Hide who you follow and who follows you.";
}
leaf post-visibility {
type enumeration {
enum public {
description
"Posts are public.";
}
enum unlisted {
description
"Posts are unlisted, though visable to all.";
}
enum followers-only {
description
"Posts only visible to followers.";
}
}
default public;
description
"The post privacy setting.";
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}
description
"Preferences for the member.";
}
leaf-list following {
type leafref {
path "/members/member/member-id";
}
description
"Other members this members is following.";
}
container posts {
description
"The member's posts.";
list post {
key timestamp;
leaf timestamp {
type yang:date-and-time;
description
"The timestamp for the member's post.";
}
leaf title {
type string {
length "1..80";
pattern '.*[\n].*' {
modifier invert-match;
}
}
description
"A one-line title.";
}
leaf body {
type string;
mandatory true;
description
"The body of the post.";
}
description
"A list of posts.";
}
}
container favorites {
description
"The member's favorites.";
leaf-list uint8-numbers {
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type uint8;
ordered-by user;
description
"The member's favorite uint8 numbers.";
}
leaf-list uint64-numbers {
type uint64;
ordered-by user;
description
"The member's favorite uint64 numbers.";
}
leaf-list int8-numbers {
type int8;
ordered-by user;
description
"The member's favorite int8 numbers.";
}
leaf-list int64-numbers {
type int64;
ordered-by user;
description
"The member's favorite uint64 numbers.";
}
leaf-list decimal64-numbers {
type decimal64 {
fraction-digits 5;
}
ordered-by user;
description
"The member's favorite decimal64 numbers.";
}
leaf-list bits {
type bits {
bit zero {
position 0;
description "zero";
}
bit one {
position 1;
description "one";
}
bit two {
position 2;
description "two";
}
}
ordered-by user;
description
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"The member's favorite bits.";
}
}
container stats {
config false;
description
"Operational state members values.";
leaf joined {
type yang:date-and-time;
mandatory true;
description
"Timestamp when member joined.";
}
leaf membership-level {
type enumeration {
enum admin {
description
"Site administrator.";
}
enum standard {
description
"Standard membership level.";
}
enum pro {
description
"Professional membership level.";
}
}
mandatory true;
description
"The membership level for this member.";
}
leaf last-activity {
type yang:date-and-time;
description
"Timestamp of member's last activity.";
}
}
}
}
container audit-logs {
config false;
description
"Audit log configuration";
list audit-log {
description
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"List of audit logs.";
leaf timestamp {
type yang:date-and-time;
mandatory true;
description
"The timestamp for the event.";
}
leaf member-id {
type string;
mandatory true;
description
"The 'member-id' of the member.";
}
leaf source-ip {
type inet:ip-address;
mandatory true;
description
"The apparent IP address the member used.";
}
leaf request {
type string;
mandatory true;
description
"The member's request.";
}
leaf outcome {
type boolean;
mandatory true;
description
"Indicate if request was permitted.";
}
}
}
}
A.2. Example Data Set
The examples assume the server's operational state as follows.
The data is provided in JSON only for convenience and, in particular,
has no bearing on the "generic" nature of the tests themselves.
{
"example-social:members": {
"member": [
{
"member-id": "bob",
"email-address": "bob@example.com",
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"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Here and now, like never before.",
"posts": {
"post": [
{
"timestamp": "2020-08-14T03:32:25Z",
"body": "Just got in."
},
{
"timestamp": "2020-08-14T03:33:55Z",
"body": "What's new?"
},
{
"timestamp": "2020-08-14T03:34:30Z",
"body": "I'm bored..."
}
]
},
"favorites": {
"decimal64-numbers": ["3.14159", "2.71828"]
},
"stats": {
"joined": "2020-08-14T03:30:00Z",
"membership-level": "standard",
"last-activity": "2020-08-14T03:34:30Z"
}
},
{
"member-id": "eric",
"email-address": "eric@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Go to bed with dreams; wake up with a purpose.",
"following": ["alice"],
"posts": {
"post": [
{
"timestamp": "2020-09-17T18:02:04Z",
"title": "Son, brother, husband, father",
"body": "What's your story?"
}
]
},
"favorites": {
"bits": ["two", "one", "zero"]
},
"stats": {
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"joined": "2020-09-17T19:38:32Z",
"membership-level": "pro",
"last-activity": "2020-09-17T18:02:04Z"
}
},
{
"member-id": "alice",
"email-address": "alice@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Every day is a new day",
"privacy-settings": {
"hide-network": false,
"post-visibility": "public"
},
"following": ["bob", "eric", "lin"],
"posts": {
"post": [
{
"timestamp": "2020-07-08T13:12:45Z",
"title": "My first post",
"body": "Hiya all!"
},
{
"timestamp": "2020-07-09T01:32:23Z",
"title": "Sleepy...",
"body": "Catch y'all tomorrow."
}
]
},
"favorites": {
"uint8-numbers": [17, 13, 11, 7, 5, 3],
"int8-numbers": [-5, -3, -1, 1, 3, 5]
},
"stats": {
"joined": "2020-07-08T12:38:32Z",
"membership-level": "admin",
"last-activity": "2021-04-01T02:51:11Z"
}
},
{
"member-id": "lin",
"email-address": "lin@example.com",
"password": "$0$1543",
"privacy-settings": {
"hide-network": true,
"post-visibility": "followers-only"
},
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"following": ["joe", "eric", "alice"],
"stats": {
"joined": "2020-07-09T12:38:32Z",
"membership-level": "standard",
"last-activity": "2021-04-01T02:51:11Z"
}
},
{
"member-id": "joe",
"email-address": "joe@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Greatness is measured by courage and heart.",
"privacy-settings": {
"post-visibility": "unlisted"
},
"following": ["bob"],
"posts": {
"post": [
{
"timestamp": "2020-10-17T18:02:04Z",
"body": "What's your status?"
}
]
},
"stats": {
"joined": "2020-10-08T12:38:32Z",
"membership-level": "pro",
"last-activity": "2021-04-01T02:51:11Z"
}
},
{
"member-id": "åsa",
"email-address": "asa@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"privacy-settings": {
"post-visibility": "unlisted"
},
"following": ["alice", "bob"],
"stats": {
"joined": "2022-02-19T13:12:00Z",
"membership-level": "standard",
"last-activity": "2022-04-19T13:12:59Z"
}
}
]
},
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"example-social:audit-logs": {
"audit-log": [
{
"timestamp": "2020-10-11T06:47:59Z",
"member-id": "alice",
"source-ip": "192.168.0.92",
"request": "POST /groups/group/2043",
"outcome": true
},
{
"timestamp": "2020-11-01T15:22:01Z",
"member-id": "bob",
"source-ip": "192.168.2.16",
"request": "POST /groups/group/123",
"outcome": false
},
{
"timestamp": "2020-12-12T21:00:28Z",
"member-id": "eric",
"source-ip": "192.168.254.1",
"request": "POST /groups/group/10",
"outcome": true
},
{
"timestamp": "2021-01-03T06:47:59Z",
"member-id": "alice",
"source-ip": "192.168.0.92",
"request": "POST /groups/group/333",
"outcome": true
},
{
"timestamp": "2021-01-21T10:00:00Z",
"member-id": "bob",
"source-ip": "192.168.2.16",
"request": "POST /groups/group/42",
"outcome": true
},
{
"timestamp": "2020-02-07T09:06:21Z",
"member-id": "alice",
"source-ip": "192.168.0.92",
"request": "POST /groups/group/1202",
"outcome": true
},
{
"timestamp": "2020-02-28T02:48:11Z",
"member-id": "bob",
"source-ip": "192.168.2.16",
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"request": "POST /groups/group/345",
"outcome": true
}
]
}
}
A.3. Example Queries
The following sections are presented in reverse query-parameters
processing order. Starting with the simplest (limit) and ending with
the most complex (where).
All the vector tests are presented in a protocol-independent manner.
JSON is used only for its conciseness.
A.3.1. The "limit" Parameter
Noting that "limit" must be a positive number, the edge condition
values are '1', '2', num-elements-1, num-elements, and num-
elements+1.
| If '0' were a valid limit value, it would always return an
| empty result set. Any value greater than or equal to num-
| elements results the entire result set, same as when "limit" is
| unspecified.
These vector tests assume the target "/example-
social:members/member=alice/favorites/uint8-numbers", which has six
values, thus the edge condition "limit" values are: '1', '2', '5',
'6', and '7'.
A.3.1.1. limit=1
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: 1
RESPONSE
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{
"example-social:uint8-numbers": [17],
"@example-social:uint8-numbers": [
{
"ietf-list-pagination:remaining": 5
}
]
}
A.3.1.2. limit=2
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: 2
RESPONSE
{
"example-social:uint8-numbers": [17, 13],
"@example-social:uint8-numbers": [
{
"ietf-list-pagination:remaining": 4
}
]
}
A.3.1.3. limit=5
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: 5
RESPONSE
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{
"example-social:uint8-numbers": [17, 13, 11, 7, 5],
"@example-social:uint8-numbers": [
{
"ietf-list-pagination:remaining": 1
}
]
}
A.3.1.4. limit=6
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: 6
RESPONSE
{
"example-social:uint8-numbers": [17, 13, 11, 7, 5, 3]
}
A.3.1.5. limit=7
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: 7
RESPONSE
{
"example-social:uint8-numbers": [17, 13, 11, 7, 5, 3]
}
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A.3.2. The "offset" Parameter
Noting that "offset" must be an unsigned number less than or equal to
the num-elements, the edge condition values are '0', '1', '2', num-
elements-1, num-elements, and num-elements+1.
These vector tests again assume the target "/example-
social:members/member=alice/favorites/uint8-numbers", which has six
values, thus the edge condition "limit" values are: '0', '1', '2',
'5', '6', and '7'.
A.3.2.1. offset=0
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: 0
Limit: -
RESPONSE
{
"example-social:uint8-numbers": [17, 13, 11, 7, 5, 3]
}
A.3.2.2. offset=1
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: 1
Limit: -
RESPONSE
{
"example-social:uint8-numbers": [13, 11, 7, 5, 3]
}
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A.3.2.3. offset=2
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: 2
Limit: -
RESPONSE
{
"example-social:uint8-numbers": [11, 7, 5, 3]
}
A.3.2.4. offset=5
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: 5
Limit: -
RESPONSE
{
"example-social:uint8-numbers": [3]
}
A.3.2.5. offset=6
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: 6
Limit: -
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RESPONSE
{
"example-social:uint8-numbers": []
}
A.3.2.6. offset=7
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: 7
Limit: -
RESPONSE
ERROR
A.3.3. The "cursor" Parameter
Noting that "cursor" must be an base64 encoded opaque value which
addresses an element in a list.
| The default value is empty, which is the same as supplying the
| cursor value for the first element in the list.
These vector tests assume the target "/example-social:members/member"
which has five members.
| Note that response has added attributes describing the result
| set and position in pagination.
A.3.3.1. cursor=&limit=2
REQUEST
Target: /example-social:members/member
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: 2
Cursor: -
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RESPONSE
{
"example-social:member": [
{
"member-id": "bob",
"email-address": "bob@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Here and now, like never before.",
"posts": {
"post": [
{
"timestamp": "2020-08-14T03:32:25Z",
"body": "Just got in."
},
{
"timestamp": "2020-08-14T03:33:55Z",
"body": "What's new?"
},
{
"timestamp": "2020-08-14T03:34:30Z",
"body": "I'm bored..."
}
]
},
"favorites": {
"decimal64-numbers": ["3.14159", "2.71828"]
},
"stats": {
"joined": "2020-08-14T03:30:00Z",
"membership-level": "standard",
"last-activity": "2020-08-14T03:34:30Z"
}
},
{
"member-id": "eric",
"email-address": "eric@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Go to bed with dreams; wake up with a purpose.",
"following": ["alice"],
"posts": {
"post": [
{
"timestamp": "2020-09-17T18:02:04Z",
"title": "Son, brother, husband, father",
"body": "What's your story?"
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}
]
},
"favorites": {
"bits": ["two", "one", "zero"]
},
"stats": {
"joined": "2020-09-17T19:38:32Z",
"membership-level": "pro",
"last-activity": "2020-09-17T18:02:04Z"
}
}
],
"@example-social:member": [
{
"ietf-list-pagination:remaining": 3,
"ietf-list-pagination:previous": "",
"ietf-list-pagination:next": "YWxpY2U=" // alice
}
]
}
A.3.3.2. cursor="YWxpY2U="&limit=2
REQUEST
Target: /example-social:members/member
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: 2
Cursor: YWxpY2U=
RESPONSE
{
"example-social:member": [
{
"member-id": "alice",
"email-address": "alice@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Every day is a new day",
"privacy-settings": {
"hide-network": false,
"post-visibility": "public"
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},
"following": ["bob", "eric", "lin"],
"posts": {
"post": [
{
"timestamp": "2020-07-08T13:12:45Z",
"title": "My first post",
"body": "Hiya all!"
},
{
"timestamp": "2020-07-09T01:32:23Z",
"title": "Sleepy...",
"body": "Catch y'all tomorrow."
}
]
},
"favorites": {
"uint8-numbers": [17, 13, 11, 7, 5, 3],
"int8-numbers": [-5, -3, -1, 1, 3, 5]
},
"stats": {
"joined": "2020-07-08T12:38:32Z",
"membership-level": "admin",
"last-activity": "2021-04-01T02:51:11Z"
}
},
{
"member-id": "lin",
"email-address": "lin@example.com",
"password": "$0$1543",
"privacy-settings": {
"hide-network": true,
"post-visibility": "followers-only"
},
"following": ["joe", "eric", "alice"],
"stats": {
"joined": "2020-07-09T12:38:32Z",
"membership-level": "standard",
"last-activity": "2021-04-01T02:51:11Z"
}
}
],
"@example-social:member": [
{
"ietf-list-pagination:remaining": 1,
"ietf-list-pagination:previous": "ZXJpYw==", // eric
"ietf-list-pagination:next": "am9l" // joe
}
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]
}
A.3.3.3. cursor="am9l"&limit=2
REQUEST
Target: /example-social:members/member
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: 2
Cursor: am9l
RESPONSE
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{
"example-social:member": [
{
"member-id": "joe",
"email-address": "joe@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Greatness is measured by courage and heart.",
"privacy-settings": {
"post-visibility": "unlisted"
},
"following": ["bob"],
"posts": {
"post": [
{
"timestamp": "2020-10-17T18:02:04Z",
"body": "What's your status?"
}
]
},
"stats": {
"joined": "2020-10-08T12:38:32Z",
"membership-level": "pro",
"last-activity": "2021-04-01T02:51:11Z"
}
}
],
"@example-social:member": [
{
"ietf-list-pagination:remaining": 0,
"ietf-list-pagination:previous": "bGlu", // lin
"ietf-list-pagination:next": ""
}
]
}
A.3.4. The "direction" Parameter
Noting that "direction" is an enumeration with two values, the edge
condition values are each defined enumeration.
| The value "forwards" is sometimes known as the "default" value,
| as it produces the same result set as when "direction" is
| unspecified.
These vector tests again assume the target "/example-
social:members/member=alice/favorites/uint8-numbers". The number of
elements is relevant to the edge condition values.
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| It is notable that "uint8-numbers" is an "ordered-by" user
| leaf-list. Traversals are over the user-specified order, not
| the numerically-sorted order, which is what the "sort-by"
| parameter addresses. If this were an "ordered-by system" leaf-
| list, then the traversals would be over the system-specified
| order, again not a numerically-sorted order.
A.3.4.1. direction=forwards
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: forwards
Offset: -
Limit: -
RESPONSE
{
"example-social:uint8-numbers": [17, 13, 11, 7, 5, 3]
}
A.3.4.2. direction=backwards
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: -
Direction: backwards
Offset: -
Limit: -
RESPONSE
{
"example-social:uint8-numbers": [3, 5, 7, 11, 13, 17]
}
A.3.5. The "sort-by" Parameter
Noting that the "sort-by" parameter is a node identifier, there is
not so much "edge conditions" as there are "interesting conditions".
This section provides examples for some interesting conditions.
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A.3.5.1. the target node's type
The section provides three examples, one for a "leaf-list" and two
for a "list", with one using a direct descendent and the other using
an indirect descendent.
A.3.5.1.1. type is a "leaf-list"
This example illustrates when the target node's type is a "leaf-
list". Note that a single period (i.e., '.') is used to represent
the nodes to be sorted.
This test again uses the target "/example-
social:members/member=alice/favorites/uint8-numbers", which is a
leaf-list.
REQUEST
Target: /example-social:members/member=alice/favorites/uint8-numbers
Pagination Parameters:
Where: -
Sort-by: .
Direction: -
Offset: -
Limit: -
RESPONSE
{
"example-social:uint8-numbers": [3, 5, 7, 11, 13, 17]
}
A.3.5.1.2. type is a "list" and sort-by node is a direct descendent
This example illustrates when the target node's type is a "list" and
a direct descendent is the "sort-by" node.
This vector test uses the target "/example-social:members/member",
which is a "list", and the sort-by descendent node "member-id", which
is the "key" for the list.
REQUEST
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Target: /example-social:members/member
Pagination Parameters:
Where: -
Sort-by: member-id
Direction: -
Offset: -
Limit: -
RESPONSE
| To make the example more understandable, an ellipse (i.e.,
| "...") is used to represent a missing subtree of data.
{
"example-social:member": [
{
"member-id": "alice",
...
},
{
"member-id": "bob",
...
},
{
"member-id": "eric",
...
},
{
"member-id": "joe",
...
},
{
"member-id": "lin",
...
}
]
}
A.3.5.1.3. type is a "list" and sort-by node is an indirect descendent
This example illustrates when the target node's type is a "list" and
an indirect descendent is the "sort-by" node.
This vector test uses the target "/example-social:members/member",
which is a "list", and the sort-by descendent node "stats/joined",
which is a "config false" descendent leaf. Due to "joined" being a
"config false" node, this request would have to target the "member"
node in the <operational> datastore.
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REQUEST
Target: /example-social:members/member
Pagination Parameters:
Where: -
Sort-by: stats/joined
Direction: -
Offset: -
Limit: -
RESPONSE
| To make the example more understandable, an elipse (i.e.,
| "...") is used to represent a missing subtree of data.
{
"example-social:member": [
{
"member-id": "alice",
...
},
{
"member-id": "lin",
...
},
{
"member-id": "bob",
...
},
{
"member-id": "eric",
...
},
{
"member-id": "joe",
...
}
]
}
A.3.5.2. handling missing entries
The section provides one example for when the "sort-by" node is not
present in the data set.
FIXME: need to finish this section...
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A.3.6. The "where" Parameter
The "where" is an XPath 1.0 expression, there are numerous edge
conditions to consider, e.g., the types of the nodes that are
targeted by the expression.
A.3.6.1. match of leaf-list's values
FIXME
A.3.6.2. match on descendent string containing a substring
This example selects members that have an email address containing
"@example.com".
REQUEST
Target: /example-social:members/member
Pagination Parameters:
Where: //.[contains (@email-address,'@example.com')]
Sort-by: -
Direction: -
Offset: -
Limit: -
RESPONSE
| To make the example more understandable, an elipse (i.e.,
| "...") is used to represent a missing subtree of data.
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{
"example-social:member": [
{
"member-id": "bob",
...
},
{
"member-id": "eric",
...
},
{
"member-id": "alice",
...
},
{
"member-id": "joe",
...
},
{
"member-id": "lin",
...
}
]
}
A.3.6.3. match on decendent timestamp starting with a substring
This example selects members that have a posting whose timestamp
begins with the string "2020".
REQUEST
Target: /example-social:members/member
Pagination Parameters:
Where: //posts//post[starts-with(@timestamp,'2020')]
Sort-by: -
Direction: -
Offset: -
Limit: -
RESPONSE
| To make the example more understandable, an elipse (i.e.,
| "...") is used to represent a missing subtree of data.
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{
"example-social:member": [
{
"member-id": "bob",
...
},
{
"member-id": "eric",
...
},
{
"member-id": "alice",
...
},
{
"member-id": "joe",
...
}
]
}
A.3.7. The "locale" Parameter
The "locale" parameter may be used on any target node.
| If this parameter is omitted, there is no default value it is
| up to the server chooses a locale. This locale is then
| reported in the result-set as the "locale" metadata value.
REQUEST
Target: /example-social:members/member
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: -
Sort-locale: sv_SE
RESPONSE
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{
"example-social:member": [
{
"member-id": "alice",
...
},
{
"member-id": "bob",
...
},
{
"member-id": "eric",
...
},
{
"member-id": "joe",
...
},
{
"member-id": "lin",
...
},
{
"member-id": "åsa",
...
}
],
"@example-social:member": [
{
"ietf-list-pagination:locale": "sv_SE"
}
]
}
REQUEST
Target: /example-social:members/member
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: -
Sort-locale: en_US
RESPONSE
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{
"example-social:member": [
{
"member-id": "alice",
...
},
{
"member-id": "åsa",
...
},
{
"member-id": "bob",
...
},
{
"member-id": "eric",
...
},
{
"member-id": "joe",
...
},
{
"member-id": "lin",
...
}
],
"@example-social:member": [
{
"ietf-list-pagination:locale": "en_US"
}
]
}
A.3.8. The "sublist-limit" Parameter
The "sublist-limit" parameter may be used on any target node.
A.3.8.1. target is a list entry
This example uses the target node '/example-social:members/
member=alice' in the <intended> datastore.
| The target node is a specific list entry/element node, not the
| YANG "list" node.
This example sets the sublist-limit value '1', which returns just the
first entry for all descendent lists and leaf-lists.
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Note that, in the response, the "remaining" metadata value is set on
the first element of each descendent list and leaf-list having more
than one value.
REQUEST
Datastore: <intended>
Target: /example-social:members/member=alice
Sublist-limit: 1
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: -
RESPONSE
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{
"example-social:member": [
{
"member-id": "alice",
"email-address": "alice@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Every day is a new day",
"privacy-settings": {
"hide-network": "false",
"post-visibility": "public"
},
"following": ["bob"],
"@following": [
{
"ietf-list-pagination:remaining": "2"
}
],
"posts": {
"post": [
{
"@": {
"ietf-list-pagination:remaining": "1"
},
"timestamp": "2020-07-08T13:12:45Z",
"title": "My first post",
"body": "Hiya all!"
}
]
},
"favorites": {
"uint8-numbers": [17],
"int8-numbers": [-5],
"@uint8-numbers": [
{
"ietf-list-pagination:remaining": "5"
}
],
"@int8-numbers": [
{
"ietf-list-pagination:remaining": "5"
}
]
}
}
]
}
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A.3.8.2. target is a datastore
This example uses the target node <intended>.
This example sets the sublist-limit value '1', which returns just the
first entry for all descendent lists and leaf-lists.
Note that, in the response, the "remaining" metadata value is set on
the first element of each descendent list and leaf-list having more
than one value.
REQUEST
Datastore: <intended>
Target: /
Sublist-limit: 1
Pagination Parameters:
Where: -
Sort-by: -
Direction: -
Offset: -
Limit: -
RESPONSE
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{
"example-social:members": {
"member": [
{
"@": {
"ietf-list-pagination:remaining": "4"
},
"member-id": "bob",
"email-address": "bob@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Here and now, like never before.",
"posts": {
"post": [
{
"@": {
"ietf-list-pagination:remaining": "2"
},
"timestamp": "2020-08-14T03:32:25Z",
"body": "Just got in."
}
]
},
"favorites": {
"decimal64-numbers": ["3.14159"],
"@decimal64-numbers": [
{
"ietf-list-pagination:remaining": "1"
}
]
}
}
]
}
}
A.3.9. Combinations of Parameters
A.3.9.1. All six parameters at once
REQUEST
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Datastore: <operational>
Target: /example-social:members/member
Sublist-limit: 1
Pagination Parameters:
Where: //stats//joined[starts-with(@timestamp,'2020')]
Sort-by: member-id
Direction: backwards
Offset: 2
Limit: 2
RESPONSE
{
"example-social:member": [
{
"@": {
"ietf-list-pagination:remaining": "1"
},
"member-id": "eric",
"email-address": "eric@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Go to bed with dreams; wake up with a purpose.",
"following": ["alice"],
"posts": {
"post": [
{
"timestamp": "2020-09-17T18:02:04Z",
"title": "Son, brother, husband, father",
"body": "What's your story?"
}
]
},
"favorites": {
"bits": ["two"],
"@bits": [
{
"ietf-list-pagination:remaining": "2"
}
]
},
"stats": {
"joined": "2020-09-17T19:38:32Z",
"membership-level": "pro",
"last-activity": "2020-09-17T18:02:04Z"
}
},
{
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"member-id": "bob",
"email-address": "bob@example.com",
"password": "$0$1543",
"avatar": "BASE64VALUE=",
"tagline": "Here and now, like never before.",
"posts": {
"post": [
{
"@": {
"ietf-list-pagination:remaining": "2"
},
"timestamp": "2020-08-14T03:32:25Z",
"body": "Just got in."
}
]
},
"favorites": {
"decimal64-numbers": ["3.14159"],
"@decimal64-numbers": [
{
"ietf-list-pagination:remaining": "1"
}
]
},
"stats": {
"joined": "2020-08-14T03:30:00Z",
"membership-level": "standard",
"last-activity": "2020-08-14T03:34:30Z"
}
}
}
}
Acknowledgements
The authors would like to thank the following for lively discussions
on list (ordered by first name): Andy Bierman, Martin Björklund, and
Robert Varga.
Authors' Addresses
Kent Watsen
Watsen Networks
Email: kent+ietf@watsen.net
Qin Wu
Huawei Technologies
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Email: bill.wu@huawei.com
Per Andersson
Cisco Systems
Email: perander@cisco.com
Olof Hagsand
SUNET
Email: olof@hagsand.se
Hongwei Li
Hewlett Packard Enterprise
Email: flycoolman@gmail.com
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