Property names in GML XPath expressions
Copyright © 2010 Open Geospatial Consortium
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3 equality tests of the form “child=value” may be used to identify a specific object property by constraining the child elements of the property. Equality tests can be logically combined using the
“and” or “or” operators.
NOTE Consider the following example:
Building nameCity hallname
addresses Address
cityBonncity streetOxfordstrassestreet
number1number Address
Address cityBonncity
streetBreitestrassestreet number5number
Address addresses
Building Filter
PropertyIsEqualTo ValueReferenceaddressesAddresscityValueReference
LiteralBonnLiteral PropertyIsEqualTo
Filter
In this example “City hall” has two address values. The following XPath expression can be used to reference the number of the first Address value:
addressesAddress[street=Oxfordstrasse]number
e The last step of the XPath expression shall be a resource property or sub-component of a resource property.
f The function schema-element may be supported.
Other standards that reference this International Standard shall declare whether implementing the schema- element function is mandatory or optional.
EXAMPLE 1 The WFS standard see ISO 19142 declares that implementing the schema-element function is
optional and defines a conformance class to test whether a WFS implementation supports that method or not.
Other standards that reference this International Standard may extend this XPath subset as required.
EXAMPLE 2 The WFS standard see ISO 19142 extends this subset by allowing the use of an accessor function
called wfs:valueOf.
Annex D defines the subset of the XPath grammar for the path expressions used in this International Standard. It follows the EBNF see ISOIEC 14977 notation defined in the XPath 2.0 specification, Appendix A “XPath
grammar” see http:www.w3.orgTRxpath20nt-bnf.
7.5 Literals 7.5.1 General considerations
This subclause defines how the XML encoding of a filter expression defined in this International Standard encodes literal values. A literal value is any part of a statement or expression which should be used as
provided.
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