HEMS monitoring and control language
RFC 1076

Document Type RFC - Unknown (November 1988; No errata)
Obsoletes RFC 1023
Last updated 2013-03-02
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Network Working Group                                         G. Trewitt
Request for Comments: 1076                           Stanford University
Obsoletes: RFC 1023                                         C. Partridge
                                                           November 1988

                  HEMS Monitoring and Control Language

                           TABLE OF CONTENTS

1.   Status of This Memo                                               1
     Introduction                                                      2
2.   Overview and Scope                                                2
3.   Overview of Query Processor Operation                             4
4.   Encoding of Queries and Responses                                 5
4.1  Notation Used in This Proposal                                    5
5.   Data Organization                                                 6
5.1  Example Data Tree                                                 7
5.2  Arrays                                                            8
6.   Components of a Query                                             9
7.   Reply to a Query                                                 10
8.   Query Language                                                   12
8.1  Moving Around in the Data Tree                                   14
8.2  Retrieving Data                                                  15
8.3  Data Attributes                                                  16
8.4  Examining Memory                                                 18
8.5  Control Operations:  Modifying the Data Tree                     19
8.6  Associative Data Access:  Filters                                21
8.7  Terminating a Query                                              26
9.   Extending the Set of Values                                      27
10.  Authorization                                                    27
11.  Errors                                                           28
I.   ASN.1 Descriptions of Query Language Components                  29
I.1  Operation Codes                                                  30
I.2  Error Returns                                                    31
I.3  Filters                                                          33
I.4  Attributes                                                       34
I.5  VendorSpecific                                                   36
II.  Implementation Hints                                             36
III. Obtaining a Copy of the ASN.1 Specification                      42


   This RFC specifies a query language for monitoring and control of
   network entities.  This RFC supercedes RFC-1023, extending the query
   language and providing more discussion of the underlying issues.

Trewitt & Partridge                                             [Page 1]
RFC 1076          HEMS Monitoring and Control Language     November 1988

   This language is a component of the High-Level Entity Monitoring
   System (HEMS) described in RFC-1021 and RFC-1022.  Readers may wish
   to consult these RFCs when reading this memo.  RFC-1024 contains
   detailed assignments of numbers and structures used in this system.
   Portions of RFC-1024 that define query language structures are
   superceded by definitions in this memo.  This memo assumes a
   knowledge of the ISO data encoding standard, ASN.1.

   Distribution of this memo is unlimited.


   This RFC specifies the design of a general-purpose, yet efficient,
   monitoring and control language for managing network entities.  The
   data in the entity is modeled as a hierarchy and specific items are
   named by giving the path from the root of the tree.  Most items are
   read-only, but some can be "set" in order to perform control
   operations.  Both requests and responses are represented using the
   ISO ASN.1 data encoding rules.


   The basic model of monitoring and control used in this memo is that a
   query is sent to a monitored entity and the entity sends back a
   response.  The term query is used in the database sense -- it may
   request information, modify data, or both.  We will use gateway-
   oriented examples, but it should be understood that this query-
   response mechanism is applicable to any IP entity.

   In particular, there is no notion of an interactive "conversation" as
   in SMTP [RFC-821] or FTP [RFC-959].  A query is a complete request
   that stands on its own and elicits a complete response.

   In order to design the query language, we had to define a model for
   the data to be retrieved by the queries, which required some
   understanding of and assumptions to be made about the data.  We ended
   up with a fairly flexible data model, which places few limits on the
   type or size of the data.

   Wherever possible, we give motivations for the design decisions or
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