| ASN.1 is the specification of data encoding; specifically it is the ISO
approved data encoding representation. The meta language used in ISO
to define data encoding is often used as a meta language to define
protocol objects within the scope of the OSI SMI or IETF SMI. However,
ASN.1 precisely is only a data encoding mechanism and is totally
inadequate as a language to fully define managed objects. IETF has
defined MIBs to define a limited number of well defined objects and
uses ASN.1 templates and/or Concise MIB notation to define the syntax
of those objects. OSI on the other hand has defined a specification
language for objects (GDMO) to define managed objects. In both cases
the objects are defined at the protocol level syntactically and the
behavior of the object is defined in textual comments.
MSL on the other hand is a DEC proprietary object definition language
that is used to represent the User Interface behavior of managed
objects. It has properties and structure to allow objects to be
defined such that the user interface can be generic rather than be
specialized for each object.
In a precise way ASN.1 and MSL are 2 entirely different things. ASN.1
tells you what you need to know to properly encode protocol objects and
MSL defines what you need to know to enroll an EMA object into an
EMA management environment.
THEY ARE NOT COMPARABLE. Yes, at first glance the ASN.1 templates of
IETF describe a set of things which MSL also describe. But MSL also
has properties that ASN.1 templates do not have.
ASN.1 can not be used as a replacement for MSL. It lacks the properties
that are required. We tried with our MIB translation tool to used
ASN.1 templates but they are ambiguous. IETF realized their
deficiencies, and have since adopted the Concise MIB syntax which
for IETF MIB objects can be used to generate MSL definitions of
objects with certain assumptions.
The more interesting question is whether GDMO can be used as a
replacement for MSL. Many of us believe that GDMO with some
enhancements can replace MSL (MSL predates GDMO by several years).
DEC is working through several ISO committees trying to get GDMO
enhanced so that it addresses those user interface properties that
are needed so that it can replace MSL.
Hope this helps!
wally
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| For more information please see the following document written by
Mark Sylor which explores this in detail, White Paper
(GDMO+, 18-Apr-1991). This can be found on FILES. Right now work on
GDMO is in its early stages only. There is a lot more work to do before
it becomes the standard around here.
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