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Subject: RE: Profiles - what do we mean by the term?
During the call today, the term "profile" was used numerous times. I am not
sure we all have a common understanding by what we mean by a "profile". In ISO
and the OGC, we use the following definition:
A
profile is a strict subset of a Standard applicable to multiple
Application Schemas. This is from ISO 19109 and is typically used in the context
of XML schema.
If
we use this definition, then a profile of CAP, or EDXL for that matter, would be
a subset - not an extension, optional or otherwise. I am not sure that this is
what we want. As soon as a group adds elements or changes the meaning of an
existing element to meet local conditions, this is NOT a profile!
I
think that several of us have been talking about is the concept of an extension.
In the OGC, we have been having a strong dialogue about a general pattern for
the development of all OGC standards. We call this model core-extension.
Sometime in 2008, the membership will approve this pattern as policy to be used
in the development of all OGC standards.
Essentially
what this means is that for most any standard (interface, payload, etc) it is
possible to define a core set of elements/functionality that has an associated
set of conformance clauses. The standard also provides guidance as to how to
define extensions. Extensions allow for adding new elements or functionality -
they do not break the core. This means that any organization implementing the
core can achieve a desired level of interoperability and feel very
confident that the core standard will not change much over a fairly long period
of time. At the same time, extensions can be developed the enable the use of the
core in other information domains, communities, programs, regions, and so forth
- again without any modifications to the core. Further, extensions need not go
through a standards organization for approval - unless the group that developed
the extension wants to go to the effort.
Now,
for a standard that is already in use and implemented, there may be some
modification required to the existing standard (core) in order to enable the
ability to define extensions. We already have some of this capability to define
extensions in EDXL-RM and perhaps in DE but I am not familiar enough with
DE.
So,
in a way, I see the evolution of CAP using the core-extension design
pattern as potentially a very positive move. CAP as we know it may stay pretty
much as is: relatively simple, fairly easy to implement, and meeting specific
requirements in a well defined community. However, we may also be
able to define a consistent approach to enabling extensions that allow for such
capabilities as the specification of alternate coordinate reference systems,
multiple coordinate reference systems, additional geometries, multiple
geometries, time, and so forth. Such an approach protects current investment,
future proofs the core standard, allows more communities to engage and use the
standard. The list of benefits is quite long and very well
documented.
I
am not trying to fan any fires here. And I definitely do not develop standards
for standards sake! I spent 25 years as a software engineer, lead design
engineer, and then chief architect for a number commercial GIS products
before joining the OGC. I am very pragmatic about how we develop and use
standards.
Time
to go watch House.
Cheers
Carl Reed, PhD
CTO and Executive Director Specification Program OGC The OGC: Helping the World to Communicate Geographically
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