1.7 Vendor-Extensible Fields
The conceptual schema definition language (CSDL) supports application-specific customization and extension through the use of annotations. These annotations allow applications to embed application-specific or vendor-specific information into CSDL. The CSDL format does not specify how to process these custom-defined structures or how to distinguish structures from multiple vendors or layers. Parsers of the CSDL can ignore annotations that are not expected or not understood.
Annotations can be of two types: AnnotationAttribute and AnnotationElement.
An AnnotationAttribute is a custom XML attribute applied to a CSDL element. The attribute can belong to any XML namespace (as defined in [XMLNS-2ED]) that is not in the list of reserved XML namespaces for CSDL. Consult the reference for each CSDL element within this document to determine whether AnnotationAttribute can be used for that element.
The reserved XML namespaces for CSDL are: