Within filter expressions, specific resource instances can be identified using the fes:ResourceId element.
The rid attribute specifies the id of the resource that shall be selected by the predicate.
The previousRid attribute may be used, in implementations that support versioning, to report the previous identifier of a resource.
For attributes version, startTime and endTime are used to navigate versions of a resource if an implementation that references this International Standard supports versioning.
If an implementation that references this International Standard does not support versioning, any value specified for these attributes shall be ignored and the predicate shall always select the single version that is available.
If an implementation that references this International Standard supports versioning, the rid shall be a system generated hash containing a logical resource identifier and a version number. The specific details of the hash are implementation dependant and shall be opaque to a client.
The version attribute may then be used to navigate the various versions of a resource.
The version attribute may be an integer N indicating that the Nth version of the resource shall be selected. The first version of a resource shall be numbered 1. If N exceeds the number of versions available, the latest version of the resource shall be selected.
The version attribute may also be date indicating that the version of the resource closest to the specified date shall be selected.
The versionAction attribute may also be the strings FIRST, LATEST, PREVIOUS, NEXT and ALL. The token FIRST shall select the first version of a resource. The token LATEST shall select the most recent version of a resource. The PREVIOUS and NEXT tokens shall select the previous or next version of a resource relative to the version specified using the rid attribute. The token ALL shall select all available version of a resource.
The attributes startTime and endTime may be used to specify a predicate that selects all versions of a resource between the specified start date and end date. The startTime and endTime attributes shall always be specified together. If the startTime and endTime are specified, the version attribute shall not be specified.
7.12
Extensions
7.12.1
General considerations
Standards that reference this International Standard may extend the filter syntax by:
a)
adding functions using the fes:Function element (see 7.6);
b)
adding new operators by defining new elements in the filter syntax.
Each of these methods can be used to extend the filter syntax, as described in 7.12.2 and 7.12.3.
Ad hoc extensions to the filter syntax are strongly discouraged because such extensions are not interoperable. Instead, extensions should be made within the context of a standard that references this International Standard.