Network Working Group N. Freed
Internet-Draft S. Vedam
Expires: August 28, 2008 Sun Microsystems
February 25, 2008
Sieve Email Filtering: Sieves and display directives in XML
draft-freed-sieve-in-xml-01
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Abstract
This document describes a way to represent Sieve email filtering
language scripts in XML. Representing sieves in XML is intended not
as an alternate storage format for Sieve but rather as a means to
facilitate manipulation of scripts using XML tools.
The XML representation also defines additional elements that have no
counterparts in the regular Sieve language. These elements are
intended for use by graphical user interfaces and provide facilities
for labeling or grouping sections of a script so they can be
displayed more conveniently. These elements are represented as
specially structured comments in regular Sieve format.
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Change History (to be removed prior to publication as an RFC
Changed representation of comments in XML to use a comment element.
Updatde references.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Grammatical structure of Sieve . . . . . . . . . . . . . . . . 4
4. XML Representation of Sieve . . . . . . . . . . . . . . . . . 5
4.1. XML Display Directives . . . . . . . . . . . . . . . . . . 7
5. Extended Example . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. Normative References . . . . . . . . . . . . . . . . . . . 13
7.2. Informative References . . . . . . . . . . . . . . . . . . 13
Appendix A. Schema for Sieves in XML . . . . . . . . . . . . . . 14
Appendix B. Stylesheet for conversion from XML . . . . . . . . . 16
Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
Intellectual Property and Copyright Statements . . . . . . . . . . 23
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1. Introduction
Sieve [RFC5228] is a language for filtering email messages at or
around the time of final delivery. It is designed to be
implementable on either a mail client or mail server. It is meant to
be extensible, simple, and independent of access protocol, mail
architecture, and operating system and it is intended to be
manipulated by a variety of different user interfaces.
Some user interface environments have extensive existing facilities
for manipulating material represented in XML. While adding support
for alternate data syntaxes may be possible in most if not all of
these environments, it may not be particularly convenient to do so.
The obvious way to deal with this issue is to map sieves into XML,
possibly on a separate backend system, manipulate the XML, and
convert it back to normal Sieve format.
The fact that conversion into and out of XML may be done as a
separate operation on a different system argues strongly for defining
a common XML representation for Sieve. This way different front end
user interfaces can be used with different back end mapping and
storage facilities.
Another issue with the creation and manipulation of sieve scripts by
user interfaces is that the language is strictly focused on
describing email filtering operations. The language contains no
mechanisms for indicating how a given script should be presented in a
user interface. Such information can be represented in XML very
easily so it makes sense to define a framework to do this as part of
the XML format. Structured comments can then be used to retain this
information when the script is converted to normal Sieve format.
Various sieve extensions have already been defined, e.g., [RFC5229]
[RFC5230] [RFC5231] [RFC5232] [RFC5233] [RFC5235], and many more are
planned. The set of extensions available varies from one
implementation to the next and may even change as a result of
configuration choices. It is therefore essential that the XML
representation of Sieve be able to accommodate Sieve extensions
without requiring schema changes. It is also desirable that Sieve
extensions not require changes to the code that converts to and from
the XML representation.
This specification defines an XML representation for sieve scripts
and explains how the conversion process to and from XML works. The
XML representation is capable of accommodating any future Sieve
extension as long as the underlying Sieve grammar remains unchanged.
Furthermore, code that converts from XML to the normal Sieve format
requires no changes to accommodate extensions, while code used to
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convert from normal Sieve format to XML only requires changes when
new control commands are added - a rare event. An XML Schema and
sample code to convert to and from XML format are also provided in
the appendices.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. Grammatical structure of Sieve
The Sieve language is designed to be highly extensible without making
any changes to the basic language syntax. Accordingly the syntax of
Sieve, defined in section 8 of [RFC5228], is entirely structural in
nature and employs no reserved words of any sort.
Structurally a sieve script consists of a series of commands. Each
command in turn consists of an identifier, zero or more arguments, a
optional test or test-list, and finally an optional block containing
another series of commands. Commands are further broken down into
controls and actions, although this distinction cannot be determined
from the grammar.
Some example Sieve controls are:
stop; <-- No arguments, test, or command block
require "fileinto"; <-- Control with a single argument
if true {stop;} <-- Control with test and command block
Some examples of Sieve actions are:
discard; <-- Action with no args, test, or command block
fileinto "folder"; <-- Action with an argument
At the time of this writing there are no controls defined that accept
both arguments and a test. Similarly, there are currently no defined
actions that allow either a test or a command block. Nevertheless,
the Sieve grammar allows such constructs to be defined by some future
extension.
A test consists of an identifier followed by zero or more arguments,
then another test or test-list. Unlike commands, tests cannot be
followed by a command block.
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Here are some examples of Sieve tests. Note that such tests have to
appear as part of a command in order to be syntactically valid:
true <-- Test with no argument or subordinate test
header "to" "me@example.com" <-- Test with several arguments
Command or test arguments can be either string lists, whole numbers
or tags. (Tags are simply identifiers preceded by a colon.) Note
that although the Sieve grammar treats single strings as a degenerate
case of a string list, some tests or actions have arguments that can
only be individual strings, not lists.
Here is an example showing the use of both a test-list and a string
list:
if anyof (not exists ["From", "Date"],
header :contains "from" "fool@example.edu") {
discard;
}
Extensions can add new controls, actions, tests, or new arguments to
existing controls or actions. Extensions can also change how string
content is interpreted, although this is not relevant to this
specification. However, it is especially important to note that so
far no Sieve extension has added a new control to the language and it
seems safe to assume that due to their nature future addition of
controls will be rare.
Finally, comments are allowed between lexical elements in a Sieve
script. It is very important that comments be preserved in the XML
representation.
4. XML Representation of Sieve
Sieve controls and actions are represented in XML as control or
action elements respectively. The command's identifier appears as a
name attribute on the element itself. This is the only attribute
allowed on controls and actions - arguments, tests, test-lists, and
nest command blocks are all represented as nested elements. While
naming the element after the control or action itself may seem like a
better choice, doing so would result in extensions changing the XML
schema.
The example Sieve controls shown in the previous section would be
represented in XML as:
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<control name="stop"/>
<control name="require"><str>fileinto</str></control>
<control name="if">
<test name="true"/><control name="stop"/>
</control>
The example Sieve actions shown above would appear in XML as:
<action name="discard"/>
<action name="fileinto"><str>folder</str></action>
The separation of controls from actions in the XML representation
means that conversion from normal Sieve format to XML has to be able
to distinguish between controls and actions. This is easily done by
maintaining a list of all known controls since experience indicates
new controls are rarely added.
Tests are represented in the same basic way as controls and actions,
that is, as a test element with a name attribute giving the test
identifier. For example:
<test name="true"/>
<test name="header"/><str>to</str><str>me@example.com</str></test>
String, number, and tag arguments are represented as str, num, and
tag elements respectively. The actual string, number, or tag
identifier appears as text inside the element. None of these
elements have any defined attributes. Several examples of arguments
have already appeared in the preceding control, action and test
examples.
String list arguments are represented as a list element which in turn
contains one or more str elements. Note that this allows the
distinction between a single string and a string list containing a
single string to be preserved. This is not essential since a list
containing a single string could simply be mapped to a string, but it
seems prudent to maintain the distinction when mapping to and from
XML.
Nested command blocks appear as a series of control or action
elements inside of an outer control or action element. No block
element is needed since an inner command block can only appear once
and only after any arguments, tests, or test-lists. For example:
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<control name="if>
<test name="anyof">
<test name="not">
<test name="exists>
<list><str>From</str><str>Date</str></list>
</test>
</test>
<test name="header">
<tag>contains</tag>
<str>from</str>
<str>fool@example.edu</str>
</test>
</test>
<action name="discard"/>
</control>
Finally, Sieve comments are mapped to a special comment element in
XML. XML comments are not used because some XML tools do not make it
convenient to access comment nodes.
4.1. XML Display Directives
Sometimes graphical user interfaces are a convenient way to provide
sieve management functions to users. These interfaces typically
summarize/annotate/group/display sieve script(s) in an intuitive way
for end users.
To do this effectively, the graphical user interface may require
additional information about the sieve script itself. That
information or "meta-data" might include, but is not limited to - a
sieve name (identifying the current sieve), whether the sieve is
enabled or disabled, the order in which the part of the sieve are
presented to the user. The graphical user interface may also choose
to provide mechanisms to allow the user to modify the script.
It is often useful for a graphical user interface to group related
sieve script elements and provide an interface that display these
groups separately so they can be managed as a single object. Some
examples include Sieve statements that together provide vacation
responders, blacklists/whitelists and other types of filtering
controls.
Some advanced graphical user interfaces may even provide a natural
language representation of a sieve script and/or an advanced
interface to present sieve statements directly to the user.
A graphical user interface may also choose to support only a subset
of action commands in the Sieve language (and its extensions) and so
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a mechanism to indicate the extent of support and characterize the
relationships between those supported action commands and test (with
its arguments) is immensely useful and probably required for clients
that may not have complete knowledge of sieve grammar and semantics.
The Sieve language contains no mechanisms for indicating how a given
script should be presented in a user interface. The language also
does not contain any specific mechanisms to represent other sorts of
meta-data about the script. Providing support for such meta-data as
part of a sieve script is currently totally implementation specific
and is usually done by imposing some type of structure on comments.
However, such information can be represented in XML very easily so it
makes sense to define a framework to do this as part of the XML
format. Implementations may choose to use structured comments to
retain this information when the script is converted to normal Sieve
format.
This XML representation defines two display directives - displayblock
and displaydata - as containers for meta-data needed by graphical
user interfaces.
The displayblock element can be used to enclose any number of sieve
statements at any level. It is semantically meaningless to the sieve
script itself. It allows an arbitrary set of attributes.
Implementations MAY use this to provide many simple, display related
meta-data for the sieve such as sieve identifier, group identifier,
order of processing, etc. This information SHOULD be preserved in
structured comments during conversion of XML to the normal Sieve
syntax.
The displaydata element supports any number of arbitrary child
elements. Implementations MAY use this to represent complex data
about that sieve such as a natural language representation of sieve
or a way to provide the sieve script directly. Again, this
information SHOULD be preserved in structured comments when
converted.
5. Extended Example
The example sieve script given in section 9 of [RFC5228] would be
represented in XML as follows:
<sieve>
<comment>
Example Sieve Filter
Declare any optional features or extensions used by the script
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</comment>
<control name="require">
<str>fileinto</str>
</control>
<comment>
Handle messages from known mailing lists
Move messages from IETF filter discussion list to filter mailbox
</comment>
<control name="if">
<test name="header">
<tag>is</tag>
<str>Sender</str>
<str>owner-ietf-mta-filters@imc.org</str>
</test>
<action name="fileinto">
<str>filter</str>
</action> <comment>move to "filter" mailbox</comment>
</control>
<comment>
Keep all messages to or from people in my company
</comment>
<control name="elsif">
<test name="address">
<tag>domain</tag>
<tag>is</tag>
<list>
<str>From</str>
<str>To</str>
</list>
<str>example.com</str>
</test>
<action name="keep"/>
</control>
<comment>
Try and catch unsolicited email. If a message is not to me,
or it contains a subject known to be spam, file it away.
</comment>
<control name="elsif">
<test name="anyof">
<test name="not">
<test name="address">
<tag>all</tag>
<tag>contains</tag>
<list>
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<str>To</str>
<str>Cc</str>
<str>Bcc</str>
</list>
<str>me@example.com</str>
</test>
</test>
<test name="header">
<tag>matches</tag>
<str>subject</str>
<list>
<str>*make*money*fast*</str>
<str>*university*dipl*mas*</str>
</list>
</test>
</test>
<action name="fileinto">
<str>spam</str>
</action>
</control>
<control name="else">
<comment>
Move all other (non-company) mail to "personal"
mailbox.
</comment>
<action name="fileinto">
<str>personal</str>
</action>
</control>
</sieve>
The same script could be annotated with graphical display hints in a
variety of ways. Two possibilities are:
<sieve>
<control name="require">
<str>fileinto</str>
</control>
<displayblock name="File filter list mail" order="1"
group="FILE_TO_FOLDER" enable="true">
<control name="if">
<test name="header">
<tag>is</tag>
<str>Sender</str>
<str>owner-ietf-mta-filters@imc.org</str>
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</test>
<action name="fileinto">
<str>filter</str>
</action>
</control>
</displayblock>
<displayblock name="Keep all company mail" order="2"
group="KEEP_MESSAGE" enable="true">
<control name="elsif">
<test name="address">
<tag>domain</tag>
<tag>is</tag>
<list>
<str>From</str>
<str>To</str>
</list>
<str>example.com</str>
</test>
<action name="keep"/>
</control>
</displayblock>
<displayblock name="File suspected spam" order="3"
group="FILE_TO_FOLDER" enable="true">
<control name="elsif">
<test name="anyof">
<test name="not">
<test name="address">
<tag>all</tag>
<tag>contains</tag>
<list>
<str>To</str>
<str>Cc</str>
<str>Bcc</str>
</list>
<str>me@example.com</str>
</test>
</test>
<test name="header">
<tag>matches</tag>
<str>subject</str>
<list>
<str>*make*money*fast*</str>
<str>*university*dipl*mas*</str>
</list>
</test>
</test>
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<action name="fileinto">
<str>spam</str>
</action>
</control>
</displayblock>
<displayblock name="File noncompany mail as personal" order="4"
group="FILE_TO_FOLDER" enable="true">
<control name="else">
<action name="fileinto">
<str>personal</str>
</action>
</control>
</displayblock>
</sieve>
Note that since displayblock elements are semantically null as far as
the script itself is concerned they can be used to group structures
like elsif and else that are tied to statements in other groups.
<sieve>
<displaydata>
<nls-interpretation>
If the e-mail header "Sender" is owner-ietf-mta-filters@imc.org
then file it into the "filter" folder.
Otherwise if the address in the "From" or "To" has a domain
that is "example.com" then keep it.
Otherwise messages meeting with any of these conditions:
(1) None of the addresses in "To" or "Cc" or "Bcc" contains
the domain "example.com".
(2) The "Subject" field matches the pattern *make*money*fast* or
*university*dipl*mas* then file it into the "spam" folder.
If all else fails then file the message in the "personal"
folder.
</nls-interpretation>
</displaydata>
... the actual sieve script ...
</sieve>
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6. Security Considerations
Any syntactically valid sieve script can be represented in XML.
Accordingly, all security considerations applicable to Sieve and any
extensions used also apply to the XML representation.
The use of XML carries its own security risks. Section 7 of RFC 3470
[RFC3470] discusses these risks.
Arbitrary data can be placed in the extensible displayblock and
displaydata constructs defined in this specification, possibly
including entire scripts in languages other than Sieve. Appropriate
security precautions should be taken when using these facilities.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3470] Hollenbeck, S., Rose, M., and L. Masinter, "Guidelines for
the Use of Extensible Markup Language (XML)
within IETF Protocols", BCP 70, RFC 3470, January 2003.
[RFC5228] Guenther, P. and T. Showalter, "Sieve: An Email Filtering
Language", RFC 5228, January 2008.
7.2. Informative References
[RFC5229] Homme, K., "Sieve Email Filtering: Variables Extension",
RFC 5229, January 2008.
[RFC5230] Showalter, T. and N. Freed, "Sieve Email Filtering:
Vacation Extension", RFC 5230, January 2008.
[RFC5231] Segmuller, W. and B. Leiba, "Sieve Email Filtering:
Relational Extension", RFC 5231, January 2008.
[RFC5232] Melnikov, A., "Sieve Email Filtering: Imap4flags
Extension", RFC 5232, January 2008.
[RFC5233] Murchison, K., "Sieve Email Filtering: Subaddress
Extension", RFC 5233, January 2008.
[RFC5235] Daboo, C., "Sieve Email Filtering: Spamtest and Virustest
Extensions", RFC 5235, January 2008.
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Appendix A. Schema for Sieves in XML
The following defines a schema for the XML representation of Sieve
scripts. Note that aside from defining the displaydata and
displayblock elements this schema imposes no constraints on their
content.
<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<xsd:element name="sieve">
<xsd:complexType>
<xsd:sequence>
<xsd:choice maxOccurs="unbounded" minOccurs="0">
<xsd:element ref="control"/>
<xsd:element ref="action"/>
<xsd:element ref="displayblock"/>
<xsd:element ref="displaydata"/>
<xsd:element ref="comment"/>
</xsd:choice>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="comment" type="xsd:string"/>
<xsd:complexType name="command">
<xsd:sequence>
<xsd:choice minOccurs="0" maxOccurs="unbounded">
<xsd:element ref="str"/>
<xsd:element ref="num"/>
<xsd:element ref="list"/>
<xsd:element ref="tag"/>
<xsd:element ref="comment"/>
</xsd:choice>
<xsd:element ref="test" minOccurs="0" maxOccurs="1"/>
<xsd:choice minOccurs="0" maxOccurs="unbounded">
<xsd:element ref="control"/>
<xsd:element ref="action"/>
<xsd:element ref="displayblock"/>
<xsd:element ref="displaydata"/>
<xsd:element ref="comment"/>
</xsd:choice>
</xsd:sequence>
<xsd:attribute use="required" name="name" type="identifier"/>
</xsd:complexType>
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<xsd:element name="control" type="command"/>
<xsd:element name="action" type="command"/>
<xsd:element name="test">
<xsd:complexType>
<xsd:sequence>
<xsd:choice minOccurs="0" maxOccurs="unbounded">
<xsd:element ref="str"/>
<xsd:element ref="num"/>
<xsd:element ref="list"/>
<xsd:element ref="tag"/>
<xsd:element ref="comment"/>
</xsd:choice>
<xsd:element ref="test" minOccurs="0"
maxOccurs="unbounded"/>
</xsd:sequence>
<xsd:attribute use="required" name="name" type="identifier"/>
</xsd:complexType>
</xsd:element>
<xsd:element name="list">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="str" minOccurs="1"
maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="tag" type="identifier"/>
<xsd:element name="str" type="xsd:string"/>
<xsd:element name="num" type="xsd:nonNegativeInteger"/>
<xsd:simpleType name="identifier">
<xsd:restriction base="xsd:token">
<xsd:pattern value="[A-Za-z_][A-Za-z0-9_]*"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:element name="displayblock">
<xsd:complexType>
<xsd:sequence>
<xsd:choice minOccurs="0" maxOccurs="unbounded">
<xsd:element ref="control"/>
<xsd:element ref="action"/>
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<xsd:element ref="displayblock"/>
<xsd:element ref="displaydata"/>
<xsd:element ref="comment"/>
</xsd:choice>
</xsd:sequence>
<xsd:anyAttribute processContents="skip"/>
</xsd:complexType>
</xsd:element>
<xsd:element name="displaydata">
<xsd:complexType>
<xsd:sequence minOccurs="0" maxOccurs="unbounded">
<xsd:any processContents="skip"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
Appendix B. Stylesheet for conversion from XML
<?xml version="1.0" encoding="UTF-8"?>
<!-- Convert Sieve in XML to standard Sieve syntax -->
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text" encoding="UTF-8"
media-type="application/sieve"/>
<!-- Only preserve whitespace in str elements -->
<xsl:strip-space elements="*"/>
<xsl:preserve-space elements="str"/>
<!-- Match top level sieve node,
start processing in sieve mode -->
<xsl:template match="sieve">
<xsl:apply-templates
select="control|action|comment()|displayblock|displaydata"
mode="sieve">
<xsl:with-param name="prefix" select="''"/>
</xsl:apply-templates>
</xsl:template>
<!-- Routine to properly literalize quotes in Sieve strings -->
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<xsl:template name="quote-string">
<xsl:param name="str"/>
<xsl:choose>
<xsl:when test="not($str)"/>
<xsl:when test="contains($str, '"')">
<xsl:call-template name="quote-string">
<xsl:with-param name="str"
select="substring-before($str, '"')"/>
</xsl:call-template>
<xsl:text>\"</xsl:text>
<xsl:call-template name="quote-string">
<xsl:with-param name="str"
select="substring-after($str, '"')"/>
</xsl:call-template>
</xsl:when>
<xsl:when test="contains($str, '\')">
<xsl:call-template name="quote-string">
<xsl:with-param name="str"
select="substring-before($str, '\')"/>
</xsl:call-template>
<xsl:text>\\</xsl:text>
<xsl:call-template name="quote-string">
<xsl:with-param name="str"
select="substring-after($str, '\')"/>
</xsl:call-template>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$str"/>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
<!-- Sieve mode processing templates -->
<xsl:template match="control|action" mode="sieve">
<xsl:param name="prefix"/>
<xsl:text xml:space="preserve">
</xsl:text>
<xsl:value-of select="$prefix"/>
<xsl:value-of select="@name"/>
<xsl:variable name="blockbegin"
select="generate-id(control|action)"/>
<xsl:for-each select="*|comment()">
<xsl:choose>
<xsl:when test="self::str|self::num|
self::list|self::tag|self::test">
<xsl:apply-templates select="." mode="sieve"/>
</xsl:when>
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<xsl:when test="generate-id(.) = $blockbegin">
<xsl:text xml:space="preserve">
</xsl:text>
<xsl:value-of select="$prefix"/>
<xsl:text>{</xsl:text>
<xsl:apply-templates select="." mode="sieve">
<xsl:with-param name="prefix"
select="concat($prefix, ' ')"/>
</xsl:apply-templates>
</xsl:when>
<xsl:otherwise>
<xsl:apply-templates select="." mode="sieve">
<xsl:with-param name="prefix"
select="concat($prefix, ' ')"/>
</xsl:apply-templates>
</xsl:otherwise>
</xsl:choose>
</xsl:for-each>
<xsl:choose>
<xsl:when test="count(control|action) > 0">
<xsl:text xml:space="preserve">
</xsl:text>
<xsl:value-of select="$prefix"/>
<xsl:text>}</xsl:text>
</xsl:when>
<xsl:otherwise>
<xsl:text>;</xsl:text>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
<xsl:template match="test" mode="sieve">
<xsl:text xml:space="preserve"> </xsl:text>
<xsl:value-of select="@name"/>
<xsl:apply-templates select="str|num|list|tag|comment()"
mode="sieve"/>
<xsl:if test="count(descendant::test) > 0">
<xsl:text> (</xsl:text>
<xsl:for-each select="test">
<xsl:apply-templates select="." mode="sieve"/>
<xsl:if test="count(following-sibling::test) > 0">
<xsl:text>,</xsl:text>
</xsl:if>
</xsl:for-each>
<xsl:text> )</xsl:text>
</xsl:if>
</xsl:template>
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<xsl:template match="str" mode="sieve">
<xsl:text> "</xsl:text>
<xsl:call-template name="quote-string">
<xsl:with-param name="str" select="text()"/>
</xsl:call-template>
<xsl:text>"</xsl:text>
</xsl:template>
<xsl:template match="num" mode="sieve">
<xsl:text xml:space="preserve"> </xsl:text>
<!-- Use numeric suffixes when possible -->
<xsl:choose>
<xsl:when test="(number(text()) mod 1073741824) = 0">
<xsl:value-of select="number(text()) div 1073741824"/>
<xsl:text>G</xsl:text>
</xsl:when>
<xsl:when test="(number(text()) mod 1048576) = 0">
<xsl:value-of select="number(text()) div 1048576"/>
<xsl:text>M</xsl:text>
</xsl:when>
<xsl:when test="(number(text()) mod 1024) = 0">
<xsl:value-of select="number(text()) div 1024"/>
<xsl:text>K</xsl:text>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="text()"/>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
<xsl:template match="list" mode="sieve">
<xsl:text> [</xsl:text>
<xsl:for-each select="str">
<xsl:apply-templates select="." mode="sieve"/>
<xsl:if test="count(following-sibling::str) > 0">
<xsl:text>,</xsl:text>
</xsl:if>
</xsl:for-each>
<xsl:text> ]</xsl:text>
</xsl:template>
<xsl:template match="tag" mode="sieve">
<xsl:text> :</xsl:text>
<xsl:value-of select="text()"/>
</xsl:template>
<xsl:template match="comment" mode="sieve">
<xsl:param name="prefix"/>
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<xsl:text xml:space="preserve">
</xsl:text>
<xsl:value-of select="$prefix"/>
<xsl:text>/*</xsl:text>
<xsl:value-of select="."/>
<xsl:value-of select="$prefix"/>
<xsl:text>*/</xsl:text>
</xsl:template>
<!-- Convert display information into structured comments -->
<xsl:template match="displayblock" mode="sieve">
<xsl:param name="prefix"/>
<xsl:text xml:space="preserve">
</xsl:text>
<xsl:value-of select="$prefix"/>
<xsl:text>/* [*</xsl:text>
<xsl:apply-templates select="@*" mode="copy"/>
<xsl:text> */</xsl:text>
<xsl:apply-templates
select="control|action|comment()|displayblock|displaydata"
mode="sieve">
<xsl:with-param name="prefix" select="$prefix"/>
</xsl:apply-templates>
<xsl:text xml:space="preserve">
</xsl:text>
<xsl:value-of select="$prefix"/>
<xsl:text>/* *] */</xsl:text>
</xsl:template>
<xsl:template match="displaydata" mode="sieve">
<xsl:param name="prefix"/>
<xsl:text xml:space="preserve">
</xsl:text>
<xsl:value-of select="$prefix"/>
<xsl:text>/* [|</xsl:text>
<xsl:apply-templates mode="copy">
<xsl:with-param name="prefix"
select="concat($prefix, ' ')"/>
</xsl:apply-templates>
<xsl:text xml:space="preserve">
</xsl:text>
<xsl:value-of select="$prefix"/>
<xsl:text> |] */</xsl:text>
</xsl:template>
<!-- Copy mode processing templates -->
<xsl:template match="*[not(node())]" mode="copy">
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<xsl:param name="prefix"/>
<xsl:text xml:space="preserve">
</xsl:text>
<xsl:value-of select="$prefix"/>
<xsl:text><</xsl:text>
<xsl:value-of select="name()"/>
<xsl:apply-templates select="@*" mode="copy"/>
<xsl:text>/></xsl:text>
</xsl:template>
<xsl:template match="*[node()]" mode="copy">
<xsl:param name="prefix"/>
<xsl:text xml:space="preserve">
</xsl:text>
<xsl:value-of select="$prefix"/>
<xsl:text><</xsl:text>
<xsl:value-of select="name()"/>
<xsl:apply-templates select="@*" mode="copy"/>
<xsl:text>></xsl:text>
<xsl:apply-templates mode="copy">
<xsl:with-param name="prefix"
select="concat($prefix, ' ')"/>
</xsl:apply-templates>
<xsl:if test="*[last()][not(text())]">
<xsl:text xml:space="preserve">
</xsl:text>
<xsl:value-of select="$prefix"/>
</xsl:if>
<xsl:text></</xsl:text>
<xsl:value-of select="name()"/>
<xsl:text>></xsl:text>
</xsl:template>
<xsl:template match="@*" mode="copy">
<xsl:text> </xsl:text>
<xsl:value-of select="name()"/>
<xsl:text>="</xsl:text>
<xsl:value-of select="."/>
<xsl:text>"</xsl:text>
</xsl:template>
</xsl:stylesheet>
Appendix C. Acknowledgements
The stylesheet copy mode code is loosely based on a sample code
posted to the xsl-list list by Americo Albuquerque. Andrew McKeon
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provided useful comments on the document.
Authors' Addresses
Ned Freed
Sun Microsystems
3401 Centrelake Drive, Suite 410
Ontario, CA 92761-1205
USA
Phone: +1 909 457 4293
Email: ned.freed@mrochek.com
Srinivas Saisatish Vedam
Sun Microsystems
Phone: +91 80669 27577
Email: Srinivas.Sv@Sun.COM
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Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
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The IETF invites any interested party to bring to its attention any
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this standard. Please address the information to the IETF at
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