Making the Schema Association Explicit in the XML Instance Document

The schema used by the Content Completion Assistant and document validation engine can be associated with the document using the

Associate Schema action. For most of the schema types, it uses the xml-model processing instruction, the exceptions being:

W3C XML Schema - The xsi:schemaLocation attribute is used.
DTD - The DOCTYPE declaration is used.

The association can specify a relative file path or a URL of the schema. The advantage of relative file path is that you can configure the schema at file level instead of document type level.

Select the Associate schema action from the Document > Schema menu or the Document toolbar to select the schema that will be associated with the XML document. The Associate Schema dialog box is displayed:

Figure: The Associate Schema Dialog Box

The available options are:

URL - Contains a predefined set of schemas that are used more often and it also keeps a history of the last used schemas. The URL must point to the schema file which can be loaded from the local disk or from a remote server through HTTP(S), FTP(S) or a custom protocol.
Schema type - Selected automatically from the list of possible types in the Schema type combo box (XML Schema, DTD, Relax NG, Relax NG Compact, Schematron, NVDL) based on the extension of the schema file that was entered in the URL field.
Public ID - Specify a public ID if you have selected a DTD.
Add additional association for embedded schematron rules - If you have selected XML Schema or Relax NG schemas with embedded Schematron rules, enable this option.
Use path relative to file location - Enable this option if the XML instance document and the associated schema contain relative paths. The location of the schema file is inserted in the XML instance document as a relative file path. This practice allows you, for example, to share these documents with other users, without running into problems caused by different project locations on physical disk.
Keep existing schema associations - Enable this option to keep the associations of the currently edited document with a Schema when you associate a new one.

The association with an XML Schema is added as an attribute of the root element. The Associate schema action adds one of the following:

xsi:schemaLocation attribute, if the root element of the document sets a default namespace with an xmlns attribute.
xsi:noNamespaceSchemaLocation attribute, if the root element does not set a default namespace.

The association with a DTD is added as a DOCTYPE declaration. The association with a Relax NG , Schematron or NVDL schema is added as xml-model processing instruction.