utypes: a proposal

[Douglas Tody]

Hi Norman -

On Thu, 30 Oct 2008, Norman Gray wrote:
> 
> ...presuming some 'cha' namespace declaration.  Making utypes
> compatible with XPath ends up looking pretty much like the existing
> proposal, except that '.'  -> '/' and the namespace prefix is repeated.

If I understand this correctly, you are suggesting changing the
basic syntax of UTYPE to replace the "." delimiters with the XPath
"/".  We cannot contemplate such a change at this point as UTYPE has
been in use for several years now, is specifed in existing standards
such as SSA and Spectrum (at least), and is used in many production
services and applications.

To avoid changing the fundamentals of UTYPEs the main things which must
not change are:

     o	The basic syntax as currently in use.

     o	The ability to use a simple string equality comparision to
     	recognize UTYPEs.  Apps do not parse UTYPEs, they just use
 	string comparision, e.g., to recognize the fields of a data
 	model.  Humans "parse" UTYPEs when they read them.

In my opinion it is not a problem that there can be multiple instances
of the same UTYPE within a namespace.  There *should* be multiple
instances of UTYPEs if multiple instances of the same data model
are present.  This can be resolved as a separate matter in many ways,
at the level of the container mechanism and access software.

 	- Doug