RFC 1024 (rfc1024) - Page 2 of 74

HEMS variable definitions

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RFC 1024                    HEMS Definitions                October 1987


MESSAGE FORMATS

   All HEMS values are conveyed between applications and entities using
   the High-Level Entity Management Protocol (HEMP) specified in RFC-
   1022.  All values specified in this memo are passed in the data
   sections of HEMP messages.  For all message types, the data section
   is a SEQUENCE of objects.  For requests, these objects are operations
   and their operands.  Replies contain a sequence of objects retrieved
   by a request.  Events contain an initial event object followed by an
   optional number of objects related to the event.

   Messages conforming to this memo should set the link field in the
   HEMP CommonHeader to 1, to indicate version 1 of HEMS.  The
   resourceId field should be set to NULL.


CONTROL LANGUAGE INSTRUCTIONS

   The HEMS Monitoring and Control Language defines a suite of
   operations which the query processor must be able to perform.  These
   operations and their operands are ASN.1 objects which are passed to
   the query processor over a network connection.  The operations and
   operands are sent in postfix form (the operation follows the
   operands). Operands are pushed onto a stack and are processed when
   the operation is encountered.

   To ensure that operations are easily recognized in the input stream,
   they are all encoded in a single application-specific type.  This
   type is shown below.

               Operation ::= [APPLICATION 1] IMPLICIT INTEGER {
                       reserved(0), get(1) begin(2), end(3),
                       get-match(4), get-attributes(5),
                       get-attributes-match(6), get-range(7),
                       set(8), set-match(9)
                   }

   When the query processor encounters an Operation object it consults
   the value to determine which operation is to be done (e.g., GET).

GENERAL COMMENTS ON OBJECTS STORED IN ENTITIES

   The High-Level Monitoring and Control Language requires the object
   space to have a tree-shaped type space.  Locating a particular object
   requires identifying that section of the tree in which the object
   resides.  (A more detailed explanation of the scheme is given in
   RFC-1023).




Partridge & Trewitt
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