An XML schema is written in a schema definition language in XML that describes the structure and other semantics of a conforming instance document. You must register the XML schema in an Oracle XML database before you can use the Oracle XML database. Before you register the XML schema, you must know the following:

• Whether the data for the XML instance documents already exists in relational tables. If this is the case, you must create Object Views for XML.

• Whether the storage model is LOB or Object Relational. This depends on which parts of the document are queried often and thus will need faster retrieval.

• Whether the XML schema document is annotated with comments to generate object data types and object tables. If not, you must create and manually map these objects to the XML schema. If the XML schema is already annotated with information to automatically generate object types and object tables, the XML database automatically generates these objects and you can insert conforming XML documents into it.

Use the XML schema to create complex types and storage elements for XML documents based on the XML schema. This type is available for Oracle version 9.2 and above.

For more information about XML schemas and Oracle XML databases, see Oracle XML DB Developer's Guide.