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Common Query Language (CQL2)
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| Definitionskos:definition | A fundamental operation performed on a collection of features is that of filtering in order to obtain a subset of the data which contains feature instances that satisfy some filtering criteria. This document specifies A filter grammar called Common Query Language (CQL2); Two encodings for CQL2 - a text and a JSON encoding. The Common Query Language (CQL2) defined in this document is a generic filter grammar that can be used to specify how resource instances in a source collection of any item type, including features, can be filtered to identify a results set. Typically, CQL2 is used in query operations to identify the subset of resources, such as features, that should be included in a response document. However, CQL2 can also be used in other operations, such as updates, to identify the subset of resources that should be affected by an operation. Each resource instance in the source collection is evaluated against a filtering expression. The filter expression always evaluates to true, false or null. If the expression evaluates to true, the resource instance satisfies the expression and is marked as being in the result set. If the overall filter expression evaluates to false or null, the data instance is not in the result set. Thus, the net effect of evaluating a filter expression is a set of resources that satisfy the predicates in the expression. The Common Query Language and its text encoding are not new, but this is the first time that the language is formally specified. The Common Query Language with the acronym CQL was originally created as a text encoding for use with implementations of the OGC Catalogue Service Implementation Specification. The language is based on the capabilities in the OGC Filter Encoding Standard, which was originally part of the Web Feature Service (WFS) Standard. The Common Query Language as specified in this document is a revision of this earlier version. While the language design including the classification of operators are consistent with the earlier specification, there have been a number of changes and existing implementations of CQL will need to be updated to process filter expressions specified by this document. This document therefore uses the acronym CQL2 to refer to the current version of the Common Query Language. |
|---|---|
| Broaderbroader | Implementation Standard |
| http://purl.org/dc/terms/createdcreated | 2024-07-26 |
| Creatorcreator | Panagiotis (Peter) A. Vretanos, Clemens Portele |
| seeAlsoseeAlso | https://docs.ogc.org/is/21-065r2/21-065r2.html |
| Statusstatus | valid |
| Notationnotation | 21-065r2 |
| Alternative LabelaltLabel | 21-065r2 |
| Common Query Language (CQL2) | |
| OGC document typedoctype | Implementation Standard |