Spectral DM document update

[Doug Tody]

Hi All -

This discussion seems to have died down for the moment; hopefully some
others will post as well, particularly as the Europeans come back online
tomorrow.

An important point here is that if we put an API in front of Spectrum,
the details of the XML serialization are not all that important.  The API
library can support multiple serializations and resolve any differences
between them, exposing an in-memory model to client applications which
is *indendent of external representation*.  If the API wants to present
vectors to the client it can turn Point objects into vectors, or extract
vectors from the columns of tables; if it wants to present a Point-model
it can turn vectors or columns into Points, or whatever is required.

The specfic XML serialization only matters much when we deal with the
XML representation directly.  This happens if we use XML schema-based
code generation tools to autogenerate a data binding, in which case if
we have an array of Points in the schema, that is what the resultant
API will present.  Another case is when XML-specific tools are used to
access the XML directly.  In this case the vector approach may again
be better, as a reference to a single node in the serialization could
recover a data vector in one step, allowing it to be easily extracted
and used in tools; otherwise such a data vector could be quite hard to
extract.  The tag-everything approach makes it easy to get at a single
array element, but not the whole array, which is the wrong approach for
something like a spectrum.

None of this has much to do with SOAP or the peculiarities of specific
SOAP implementations, or where SOAP is appropriate to use or otherwise.
That is an important issue too, which has not been adequately discussed,
but is largely a separate issue.

	- Doug