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Subject: RE: [emix] New Power Item Type proposals
I have attached the list of unit
enumerators with the documentation on usage. Note that for example VA has the
comment: “Apparent power in volt ampere”. The associated UML has VA as the initial
value for unit as part of the ApparentPower class. If you are worried about
misuse, I suppose this could be coded as a restriction pattern in the schema,
although I have not seen it handled like that. Bruce
Bartell Xtensible Solutions From: Toby Considine
[mailto:tobyconsidine@gmail.com] On Behalf Of
Toby Considine I
have been developing and coding with the proposed changes to the POWER.XSD and
they allow some very strange outcomes. If I follow the schema, and use no
knowledge I have already, Apparent Power can be expressed in a number of units,
including Ohms, Radians, Degrees, Hertz, and Kilograms/Joule (and many others).
This reduces the usability of the schema and makes many obviously invalid
information exchanges (in terms of “you can’t buy that”)
fully valid (in schema validation terms). This reduces the utility and value of
the artifacts produced in inter-domain exchanges. They
also break compatibility between the unification of measurement types urged by
PAP10, in that they establishes special sub-classes of names of units and for
that are used within Power that are used for no other areas of emix, for
example, in quality measures, or in pollution warrants. By restricting in the
schema all measurement types to a defined set only useful for power, they will
require revisions to the standard to extend the classes to new metrics, say to
new pollutant types, or to include carbon trading. If we reduce the base
fungibility of measurements in this way, we decrease the ability of EMIX-based
systems to respond to new market dynamics and new market regulations without
returning to the standards cycle. This sort of hindrance to adaptability
violates a core precept of EMIX which is to enable more rapid productization of
technologies and energy approaches. EMIX
as it has grown establishes some core models for exchanging information about
products whose value changes with time of delivery. Power is but one of these.
Certificates / Pollutants / carbon trading / et al. are significant others that
are closely tied to power markets, and are likely to be more so in the future.
These markets are much more changeable than the base power exchanges. Power
quality metrics vary distinctly between US, European, and Asian market already.
We want to make sure that our approach handles these different metrics,
including ones we do not know, without returning to the standards process. EMIX
already has a clear distinction between the base schema, and the particular
instantiation of its extensions for power. Other groups are already looking at
developing their own extensions for other energy-related products whose value
changes with time. There are discussions underway about using domain extensions
for the distribution of natural gas, low pressure steam, high pressure steam,
chilled water, and other district-based distributions. When we move to an
exceptionality for power, we reduce the power of the results. None
of this is meant in any way to deprecate the importance of alignment with the
IEC TC57 CIM, particularly as the IEC itself continues its growing alignment
with ISO where there subject matters overlap. I mean instead to that we have
not achieved the optimal alignment. Of course, we need to keep ever mindful
that alignment is not the same as unity. tc “The
single biggest problem in communication is the illusion that it has taken
place.”
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