[Auscope-geosciml] service architecture [SEC=UNCLASSIFIED]

Ben Caradoc-Davies Ben.Caradoc-Davies at csiro.au
Fri Sep 18 01:26:52 EDT 2009


On 17/09/09 07:28, Oliver.Raymond at ga.gov.au wrote:
>> “...Can WFS queries be specified against base classes or substitution groups of polymorphic types?
> Do you mean like when a gsml:Fault (eg, gml:name = Lake George Fault) is also a gsml:Contact?

I am more concerned about how to query a property whose concrete type is 
not known. You may only know the base type. The MappedFeature 
specification/GeologicUnit/name is just an example.

Suppose you have a feature type A with property "x", and two derived 
feature types B and C. In ASCII UML:

+---+
| A |  <--- A
+---+
| x |  <--- B
+---+

B and C inherit property "x" from A. If a feature type F has a property 
"a" of type A, then you do not know if, for a particular feature 
instance, if it is an A, B, or C, but you do know that they all have an 
"x". Should you be able to make a PropertyEquals query for a particular 
value of x:

a/A/x

(In XSD: This is situation implemented as element A with type AType 
[includes property "x"], element B with type BType, and element C with 
type CType, and BType extends Atype, and CType also extends AType. 
Feature F is defined as element F of type FType. FType has a property 
"a" of APropertyType, which contains an AType, whose substitution group 
comprises AType, Btype, CType.)

> Could you give a real world example when a GeologicUnit would have the same name as a GeologicStructure?

Sorry, I am not a geologist. I cannot distinguish rock from concrete. I 
was even taken in by the fibreglass "basalt" at the Haast visitor 
centre. I will use abstract examples in future.

> If you deliver individual geologic feature types in separate WFS services (like we did in Testbed 3), then you don’t get the problem of dealing with mixed geologic feature types.

Doesn't that defeat the purpose of using a WFS, which is intended to 
deliver multiple feature types?

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



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