[Auscope-geosciml] RE : [ExternalEmail] Re: RE : RE : service architecture [SEC=UNCLASSIFIED]

Ben Caradoc-Davies Ben.Caradoc-Davies at csiro.au
Thu Sep 24 01:37:04 EDT 2009


On 18/09/09 17:30, Boisvert, Eric wrote:
> in a/*/c/D, the * can only match all substitution of B  and you can't specify you just want M and its descendants.
[...]
> So you are right, '*' is only a partial solution.

a/*/c allows you to select features with property "a" having a property 
"c". Type defined by having a property with a particular name is known 
as "duck typing":
http://en.wikipedia.org/wiki/Duck_typing

This is not the static typing we have come to expect from working with 
UML/XSD. However, duck typing is known to work in practice, and is 
widely used in dynamically-typed languages such as Python.

If schema designers are happy for polymorphic queries to be limited to 
duck type, and not require consideration of inheritance, then XPath will 
be satisfactory.

Kind regards,

-- 
Ben Caradoc-Davies <Ben.Caradoc-Davies at csiro.au>
Software Engineer, CSIRO Earth Science and Resource Engineering
Australian Resources Research Centre
26 Dick Perry Ave, Kensington WA 6151, Australia



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