GWS Splinter: XSD Schema Evolution

[Mark Taylor]

Paul,

On Fri, 3 Jul 2015, Paul Harrison wrote:

> actually you can see this fleshed out into a first draft at  
> 
> https://code.google.com/p/volute/source/browse/trunk/projects/grid/notes/schema-versioning/schemaVersioning.tex

I hadn't seen that before; from a quick scan it looks in good shape,
and answers some of the other questions I had on this subject.

> > I haven't been through the diff of the 1.0 and 1.1-PR versions
> > of the schema with a fine toothcomb, but I can see at least
> > one incompatibility: in the 1.1-PR version, the "version"
> > attribute of the job and jobs elements is required, so
> > older instances of this document (which lack that attribute)
> > are invalid against the new version of the schema.
> 
> This anomaly comes about in trying to make the transition to the new “rules” for schema evolution for UWS.
> The intention being that the version attribute is the way to distinguish between minor versions of the standard, and 
> therefore because of its importance it was made mandatory in the 1.1 schema. However, I can see that this
> does itself break the rule that we had laid down of not introducing mandatory new elements/attributes.
> 
> I think that perhaps the best way to solve this is to make it formally optional in the schema, but in the standard document
> make it a “must” for the server to use. In the next major revision of the standard, it can be made mandatory.

Thanks, that sounds like an excellent solution.
I have included a note about this issue in my comments on the
UWS11RFC wiki page.

Mark

--
Mark Taylor   Astronomical Programmer   Physics, Bristol University, UK
m.b.taylor at bris.ac.uk +44-117-9288776  http://www.star.bris.ac.uk/~mbt/