Schemas That Use Other Schemas

Overview

When your schemas become large and complex, or when the schemas that represent your different types of instance messages have some portions in common, it can be useful to combine smaller schemas into the schemas that ultimately define the structure of the instance messages you plan to exchange with trading partners. For example, you might have multiple message types that require a shipping address to be expressed within them. You can define the structure of a shipping address in a single schema, and then use that schema within other schemas that define, for example, Order, Invoice, and Shipping Notice message schemas.

Import, include, and redefine

XML Schema definition (XSD) language provides three related mechanisms for using multiple schemas together that BizTalk Editor supports. The following table summarizes the characteristics of these mechanisms, as defined by XSD.

Multischema mechanism	Usage scenario
Import	- Accesses and uses types defined in the imported schema. - Must use types in the imported schema as is, or derive new types from them; no type modification allowed. - Provides a mechanism for using types defined in other namespaces. Indeed, an imported schema must have a target namespace that is different from the importing schema. - Uses the import element and its namespace and schemaLocation attributes to reference the other schema.
Include	- Accesses and uses types defined in the included schema. - Must use types in the included schema as is, or derive new types from them; no type modification allowed. - The included schema must be in the same target namespace as the including schema, or the target namespace of the included schema must be empty. - Uses the include element and its schemaLocation attribute to reference the other schema.
Redefine	- Accesses and uses types defined in the redefined schema. - Can use types in the redefined schema as is, derive new types from them, or specify modifications to them. - The redefined schema must be in the same target namespace as the redefining schema, or the target namespace of the redefined schema must be empty. - Uses the redefine element and its schemaLocation attribute to reference the other schema. Any type redefinitions are specified with the redefine element. Note: Using the redefine mechanism is an advanced XSD concept and should only be used after you have sufficient understanding of how and when it should be used.

Note

For complete information about the differences and similarities between the import, include, and redefine mechanisms, see the references listed in XSD Resources on the Web.

Important details

To use a type defined in one schema (Schema1) within another schema (Schema2), you must provide a reference to Schema1 within Schema2. To do so, use the Imports property of the Schema node in Schema2. When you click the ellipsis (...) button in the Imports property field, the Imports dialog box opens. In the Import New Schema as drop-down list, select XSD Import, XSD Include, or XSD Redefine. Then click Add to open the BizTalk Type Picker dialog box and browse within your BizTalk project to select Schema1.

For detailed instructions about these steps, see Creating Schemas That Use Other Schemas.

When you use the Imports dialog box to import, include, or redefine another schema, one or more of the XSD elements import, include, and redefine is added to the XSD representation of your schema, including the appropriate attributes and attribute values. Further, in the case of the import element, a prefix declaration for the namespace of the other schema is added to the schema element.

All global types (such as ComplexTypes, SimpleTypes, element groups, attribute groups) in an imported/included/redefined schema are automatically available for use within the schema in which the former schema is imported, included, or redefined. For example, global ComplexTypes defined in an imported/included/redefined schema are added to the drop-down list of the Data Structure Type property for all of the Record nodes in the importing, including, or redefining schema. More details on this property in the UI guidance and developers API namespace reference.

See Also

About Schemas
Create Schemas That Use Other Schemas
Create References to Another Node or Type