Comments on ADQL-0.7

I agree with most of Tony's comments. As the version number creeps towards the magic number 1.0 we really ought to make this look more like a specification, and not merely a casual description. The language used needs to be tightened up to make it clear what is required and what optional.

If essential parts of the specification have to be given only in the form of .xsd files, then these also have to be referenced properly, with a URL to the master copy in some repository, and brought under version control. But I think that for the benefit of any astronomers who might be curious, it is extremely desirable that this document should also include a text description of the features of the SkyQL/ADQL language. Maybe this can be done by reference to an existing specification of SQL, e.g. the entry level of SQL92, I don't know?

The list of functions is now identical to that in section 1 of appendix C of the JDBC-3.0 specification, as downloadable from http://java.sun.com/products/jdbc/index.jsp - maybe it's worth stating that?

The schema diagrams are indeed illegible, and even than only show a very small part of the schema. I don't their presence adds much. A few paragraphs of text explaining the facilities in outline would be better.

The REGION spec is also important, and again only referenced by an xml. Google found several versions for me, it's not clear which is the master.

The only reference here is an example:
  Region('CIRCLE J2000 19.5 -36.7 0.02')

The alternatives to CIRCLE need to be specified; as do the possible equinoxes as alternatives to J2000. I presume the other values are in degrees, but this is nowhere stated.

This brings me on to another topic, what units are to be used by ADQL queries, and how do users (and software) find out? But I'll post something on that separately.

-- 
Clive Page
Dept of Physics & Astronomy,
University of Leicester,    Tel +44 116 252 3551
Leicester, LE1 7RH,  U.K.   Fax +44 116 252 3311