The Capabilities vocabulary aims to provide a way for service authors to describe certain capabilities of an OData Service. There are some capabilities which are strongly recommended for services to support even though they are optional. Support for $top and $skip is a good example as supporting these query options helps with performance of a service and are essential. Such capabilities are assumed to be default capabilities of an OData service even in the case that a capabilities annotation doesn’t exist. Capabilities annotations are mainly expected to be used to explicitly specify that a service doesn’t support such capabilities. Capabilities annotations can as well be used to declaratively specify the support of such capabilities. On the other hand, there are some capabilities that a service may choose to support or not support and in varying degrees. $filter and $orderby are such good examples. This vocabulary aims to define terms to specify support or no support for such capabilities. A service is assumed to support by default the following capabilities even though an annotation doesn’t exist: - Countability ($count, $inlinecount) - Client pageability ($top, $skip) - Expandability ($expand) - Indexability by key - Batch support ($batch) - Navigability of navigation properties A service is expected to support the following capabilities. If not supported, the service is expected to call out the restrictions using annotations: - Filterability ($filter) - Sortability ($orderby) - Queryability of top level entity sets - Query functions A client cannot assume that a service supports certain capabilities. A client can try, but it needs to be prepared to handle an error in case the following capabilities are not supported: - Insertability - Updatability - Deletability