Table of contents

Appendices

5.6 schemaLocation

XML Schema uses the schemaLocation and xsi:schemaLocation attributes in three circumstances.

ref401. In an instance document, the attribute xsi:schemaLocation provides hints from the author to a processor regarding the location of schema documents. The author warrants that these schema documents are relevant to checking the validity of the document content, on a namespace by namespace basis. For example, we can indicate the location of the Report schema to a processor of the Quarterly Report:

NOTE: 

Using schemaLocation in the Quarterly Report, 4Q99html.xml

<purchaseReport
  xmlns="http://www.example.com/Report"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.example.com/Report
  http://www.example.com/Report.xsd"
  period="P3M" periodEnding="1999-12-31">

  <!-- etc. -->

</purchaseReport>

The schemaLocation attribute contains pairs of values: The first member of each pair is the namespace for which the second member is the hint describing where to find to an appropriate schema document. The schemaLocation attribute value consists of one or more pairs of URI references, separated by white space. The first member of each pair is a namespace name, and the second member of the pair is a hint describing where to find an appropriate schema document for that namespace. The presence of these hints does not require the processor to obtain or use the cited schema documents, and the processor is free to use other schemas obtained by any suitable means, or to use no schema at all.

A schema is not required to have a namespace (see [Undeclared Target Namespaces]) and so there is a noNamespaceSchemaLocation attribute which is used to provide hints for the locations of schema documents that do not have target namespaces.

2. In a schema, the include element has a required schemaLocation attribute, and it contains a URI reference which must identify a schema document. The effect is to compose a final effective schema by merging the declarations and definitions of the including and the included schemas. For example, in [Advanced Concepts II: The International Purchase Order], the type definitions of Address, USAddress, UKAddress, USState (along with their attribute and local element declarations) from address.xsd were added to the element declarations of purchaseOrder and comment, and the type definitions of PurchaseOrderType, Items and SKU (along with their attribute and local element declarations) from ipo.xsd to create a single schema.

3. Also in a schema, the import element has optional namespace and schemaLocation attributes. If present, the schemaLocation attribute is understood in a way which parallels the interpretation of xsi:schemaLocation in (1). Specifically, it provides a hint from the author to a processor regarding the location of a schema document that the author warrants supplies the required components for the namespace identified by the namespace attribute. To import components that are not in any target namespace, the import element is used without a namespace attribute (and with or without a schemaLocation attribute). References to components imported in this manner are unqualified.

Note that the schemaLocation is only a hint and some processors and applications will have reasons to not use it. For example, an XHTML editor may have a built-in XHTML schema.