> Date: Tue, 2 Sep 2003 12:07:36 +0100
> From: "Matthew J. Dovey" <[log in to unmask]>
>
> In XCQL the type of term could be relaxed to allow any XML structure e.g.
>
> <index>geo.countryBorders</index>
>   <relation>within</relation>
>   <term>
>     <gils:boundingRect xmlns:gils="urn:gils.org:termTypes">
>       <gils:point>13N25W</gils:point>
>       <gils:point>25S70E</gils:point>
>     </gils:boundingRect>
>   </term>
> </searchClause>

Yes.

> How to encode in CQL?
> option 1: direct escaped encoding?
>
> geo.countryBorders within "&lt;gils:boundingRect xmlns:gils="urn:gils.org:termTypes"&gt&lt;gils:point&gt;13N25W&lt/gils:point&gt;..."

CQL itself has nothing to do with XML, so it would be silly -- and
unnecessary -- to apply an XML encoding to the string.  There's no
need to protect '<' and '>', which are not special characters in CQL
term strings.  But we _do_ need to protect '"', which _is_ a special
character -- the only one, in fact.

So if we go this route at all, we should use
        geo.countryBorders within "<gils:boundingRect xmlns:gils=\"urn:gils.org:termTypes\"&gt<gils:point>13N25W&lt/gils:point>..."
(as the existing specification already nails down.)

> option 2: different bespoke string based encoding
>
> geo.countryBorders within "boundingRect(13N25W,25S70E)"

Fine by me.  I think we should endeavor to preserve CQL's design goal
of being human-readable, and this approach is much more conducive to
that goal than embedding an ugly hunk of XML.  There's precedent, of
course: XPath is a string-based syntax that very deliberately does
_not_ use XML for reasons of readability.

> Questions: how to ensure that this is recognised as a structure not
> as a string? (or just define this for the particular index
> geo.countryBorders must be a structure of this form).

The proposal already on the table is to define relation modifiers to
indicate the "type" of the term, e.g.
         gils.location =/point "34,76"
         gils.location within/rect "34,76 36,78"
Works for me.

 _/|_    _______________________________________________________________
/o ) \/  Mike Taylor  <[log in to unmask]>  http://www.miketaylor.org.uk
)_v__/\  "Have you killed anyone?" / "Yes, but they were all bad" --
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