VOSI: capabilities

[Matthew Graham]

Hi Ray,

I think that we can incorporate this into the current Availability  
schema and please feel free to propose what to put in it.

	Cheers,

	Matthew


On Oct 26, 2009, at 11:02 PM, Ray Plante wrote:

> Hi GWSers,
>
> I've been looking at how we can tighten both the VOSI and TAP  
> specifications to clarify exactly what a TAP service should return  
> for its capability metadata (S2.1 in VOSI, http://www.ivoa.net/Documents/VOSI/20090825/WD-VOSI-1.0-20090825.html) 
> . It seems to me that we probably need to be more specific about the  
> representation of this metadata.
>
> The form of the capability metadata is currently described in this  
> paragraph:
>
>  The service metadata shall be represented as an XML document which
>  contains a sequence of one or more elements of type
>  {http://www.ivoa.net/xml/VOResource/v1.0}Capability or sub-types
>  thereof.
>
> I see a few issues with this:
>
>  1.  I believe the intent here is that the XML document has an  
> arbitrary
>      root element containing direct child elements (as a sequence) of
>      type vr:Capability; however, it is actually ambiguous.  It seems
>      that the sequence could have any number of ancestors (i.e.  
> elements
>      between it and the root element) and still be compliant with this
>      statement.
>
>  2.  Even if we have eliminated the ambiguity of (1) above, I think we
>      need to provide an explicit schema to use for this document (as
>      VOResource is not sufficient).  This schema would define a root
>      element that takes a sequence of elements of type Capability.
>      Without this, either implementors would have to provide their own
>      custom schemas that do the same (and post them on-line) or we  
> would
>      be faced with responses that are not validate-able using standard
>      XML Schema techniques.
>
> To address these, we need to first be more explicit about the XML  
> layout. If provide the schema, then doing so is easier: we say, must  
> be compliant with XXX schema with the root element xxx:xxx.
>
> Assuming we do provide a schema, the question becomes how.  The  
> document already provides a simple schema for the availability  
> metadata (namespace http://www.ivoa.net/xml/Availability/v0.4).  We  
> could add a new global element for capabilities to this schema, but  
> we should probably change the namespace name (to, say, http://www.ivoa.net/xml/VOSI/v1.0) 
> . If we have some entrenchment with http://www.ivoa.net/xml/Availability/v0.4 
>  (which I doubt we do), then we would need a second schema.  Any  
> preferences?  May I propose a new schema?
>
> cheers,
> Ray
>