edits to bridge VOSI-TAP gap

[Ray Plante]

Hi TAPpers,

A few people (most notably, Tom McGlynn) have noted a gap between the TAP
specification of the getCapabilities() and the specification in VOSI that
makes it unclear exactly how to implement this operation for TAP.  I would
therefore like to propose specific changes to these documents intended to
close this gap.  This email specifically addresses TAP.  (See my message 
to the grid list, http://www.ivoa.net/forum/grid/0910/0738.htm, for the 
recommendations for VOSI.)

So to clarify in TAP what is needed from the getCapabilities function, 
I propose we add the following into section 2.7.2 (VOSI), just after
the first paragraph (which ends with "as defined by the VOSI standard 
[6]."):

    Note:
    The VOSI standard specifies that the capability metadata is encoded
    as an XML document which lists each of the service's capabilities as
    a <capability> element.  The type of this element (which defines its
    contents) is {http://www.ivoa.net/xml/VOResource/v1.0}Capability from
    the VOResource XML standard [8].

   In addition, the capabilties output must also comply with the following
   requirements:

    *  the returned document must include one <capability> element that
         describes the service's support for this protocol,
    *  this <capability> element describing its for TAP must have its
         "standardID" attribute set to "ivo://ivoa.net/std/TAP",
    *  this capability element must include at least one "<interface>"
         element with its "role" attribute set to "std",
    *  this "<interface>" element must contain a child "<accessURL>"
         element with the attribute "use" set to "base" which contains
         the root web resource for the service as defined in section
         2.2

    Note:
    VO registries recognize a service's support for a standard protocol
    through this capability description.  In particular, a different
    standard Capability sub-type is used for each standard protocol to
    provide capability metadata that is specific to that protocol.  At the
    time of this writing, a Capability sub-type for TAP has not yet been
    defined.  Thus for compliance with this standard, any legal Capability
    description that meets the above restrictions is sufficient.  However,
    once a VOResource extension for TAP is standardized, it is strongly
    recommended that TAP services emit its capabilities using that the
    Capability sub-type specialized for TAP.

   For example, the returned capabilities document for a service supporting
   TAP might look as follows:

     <?xml version="1.0" encoding="UTF-8"?>
     <vosi:capabilities xmlns=""
             xmlns:vosi="http://www.ivoa.net/xml/VOSI/v1.0"
             xmlns:vs="http://www.ivoa.net/xml/VODataService/v1.0"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://www.ivoa.net/xml/VOSI/v1.0
                                 http://www.ivoa.net/xml/VOSI/v1.0
                                 http://www.ivoa.net/xml/VODataService/v1.0
                                 http://www.ivoa.net/xml/VODataService/v1.0">

        <vosi:capability standardID="ivo://ivoa.net/std/TAP">
           <interface xsi:type="vs:ParamHTTP">
              <accessURL use="base"> http://myarchive.net/myTAP </accessURL>
           </interface>
        </vosi:capability>

        <vosi:capability standardID="ivo://ivoa.net/std/VOSI#capabilities">
           <interface xsi:type="vs:ParamHTTP">
              <accessURL use="full"> http://myarchive.net/myTAP/capabilities </accessURL>
           </interface>
        </vosi:capability>

        <vosi:capability standardID="ivo://ivoa.net/std/VOSI#availability">
           <interface xsi:type="vs:ParamHTTP">
              <accessURL use="full"> http://myarchive.net/myTAP/availability </accessURL>
           </interface>
        </vosi:capability>

        <vosi:capability standardID="ivo://ivoa.net/std/VOSI#tables">
           <interface xsi:type="vs:ParamHTTP">
              <accessURL use="full"> http://myarchive.net/myTAP/tables </accessURL>
           </interface>
        </vosi:capability>
     </vosi:capabilities>

The 2 Note paragraphs should use formatting used in section 2.3.4 to 
indicate that its status as non-normative comments on the normative text. 
The example should also use the appropriate formatting.

cheers,
Ray