Re: XML-QL
Jonathan Robie (jonathan@texcel.no)
Sat, 31 Oct 1998 11:36:23 -0500
At 11:19 AM 9/1/98 +0100, Michael Kay wrote:
>My immediate reaction is to compare this not with SQL, but
>with the new XSL "tree construction" facilities which
>essentially provide an XML transformation language. I don't
>have time to do a detailed point-by-point comparison but it
>would certainly be a useful exercise. Conceptually they have
>many similarities but there are many points of detail where
>one is stronger than the other. I would think it is entirely
>possible to devise a language that combines the power of
>both without a significant loss of usability.
In fact, at Metastructures 98 I presented a language called XQL that uses a
syntax very similar to XSL Patterns. This language was developed primarily
by Joe Lapp of webMethods and me. Like XML-QL, XQL is declarative.
One of the significant differences between XML-QL and XQL is that XQL can
do both hierarchy and sequence. The fundamental structural relationships in
XQL are:
o hierarchy
o parent/child
o ancestor/descendant
o sequence
o precedes
o immediately precedes
o position
o subscripts
o ranges
I think sequence is pretty important in documents, though it is not
important in many data-oriented systems. XML-QL's heritage in relational
theory has caused it to ignore sequence.
Jonathan
jonathan@texcel.no
Texcel Research
http://www.texcel.no