Proposed schemas for VOResource v0.10
(revision 2)
To address the major issues dicussed in the
IVOA Note
Lessons Learned Using VOResource in the NVO, the
following revisions to the VOResource XML schema and its extensions
are proposed. The main changes reflect two recommendations from a
recent workshop on the Resource metadata schemas. These are:
- To move to a model built more around reusable XML types rather
than reusable elements. Use of substitution groups is dropped
in favor of xsi:type to achieve polymorphism.
- To restructure the metadata to more closely match the names and
implied structure defined in the
IVOA
Recommendation, Resource Metadata for the Virtual
Observatory.
These recommendations were approved by the IVOA Registry Working Group (RWG).
In addition, the RWG recommended additional changes (resulting in revision 2):
- drop the referenceURL attribute from the ResourceName type.
- drop the logical-id attribute from the Relationship type.
- identify standard services (e.g. ConeSearch, SIA) as a resource
subtype, rather than as a subtype of Capability*
- remove definition of root element from VOResource-v0.10.xsd;
leave this to be defined by the application as necessary.
*Note: this last
recommendation led to significant changes in the Service Resource
model.
These recommendations were applied to the latest, working draft
VOResource family of schemas, resulting in the following revisions:
To see illustrations about how these changes affect what the instance
documents actually look like, review the example instance files
below:
- organisation.xml: describing
the Radio Astronomy Imaging Group (RAI) at NCSA
- registry.xml: describing the
publishing registry at NCSA.
- authority.xml: decribing the
"ncsa.adil" authority ID and RAI's ownership of it.
- collection.xml: describing the
ADIL as a data collection.
- webform.xml: describing an existing
browser-based web-form page as a service.
- conesearch.xml: describing the
ADIL Cone Search implentation (inludes description of input
parameters).
- sia.xml: describing the ADIL
implementation of the Simple Image Access Protocol (includes
description of the output VOTable with its columns).
Note about the root element: The VOResource schema no
longer defines global elements to be used as document roots; applications
should define these in their own schema, importing the VOResource core
schema and any of its extensions as necessary. In the
examples above, no such "document schema" is necessary to
legally verify. According to the XML Schema standard
(Part
1, Sect. 3.3.2, clause 1.2), the use of xsi:type in the root
element is sufficient for defining its type.
You can download all the revised schemas and the above examples in one
file. Because the schemas are not yet released working drafts
(i.e. they are internal drafts that have not been posted to
http://www.ivoa.net/xml), schemaLocation attributes have
been set to assume all of the schemas are found in the current working
directory; this will allow you to readily use XML tools with them.
Download one of the following files:
Last modified: Tue Jun 22 12:36:36 2004