Declaring transactional consistency Transactional consistency of response paging

Copyright © 2010 Open Geospatial Consortium 31 This International Standard defines two types of query expressions; ad hoc query expressions and stored query expressions. Ad hoc query expressions are encoded in XML using the element wfs:Query. They are called ad hoc because the query is not stored by the server and is only known at runtime. Stored query expression are encoded in XML using the wfs:StoredQuery element. A stored query expressions is a query that has been previously saved in the servers data store and can be executed at any time using the querys identifier. Both query expression types are derived from the abstract query expression elements defined in Clause 6 of ISO 19143:2010. 7.9.2 Ad hoc query expression 7.9.2.1 Request Semantics An ad hoc query expression may be used in a GetPropertyValue see Clause 10, GetFeature see Clause 11, GetFeatureWithLock see Clause 13 or LockFeature see Clause 12 operation to identify the set of features to be operated upon. As shown in Figure 8, an ad hoc query expression contains a typeNames parameter, projection clause, a selection clause and a sorting clause. The mandatory typeNames parameter lists the name of one or more feature types to query. The optional projection clause identifies a subset of optional feature properties that shall be presented in the result set. The projection clause for XML-encoded ad hoc query expressions may also be used to control, on a per-property basis, how resource references see 7.6.4 are resolved in the response document. NOTE How resource references are resolved in a response document can only be controlled at the operation level for KVP-encoded requests. This is accomplished using the RESOLVE, RESOLVEDEPTH and RESOLVETIMEOUT keywords see 7.6.4.3. This is in contrast to XML-encoded requests where resource resolution can be controlled at the operation and property levels. The optional selection clause specifies criteria that conditionally select features from a servers data store. The optional sorting clause specifies how the features in the response document should be ordered. An ad hoc query also allows a CRS to be asserted and used when presenting feature geometries in a response document.