4.11 Importing and including schemas

If an XSD schema becomes too large, it can be split in several smaller pieces. The pieces are assembled into a global schema by means of an XSD <import>  or <include> directive. This feature also makes it possible to share resource kind definitions across several contracts. The shared definitions are placed in a separate schema resource which is imported by several contract schemas.

For example, the global CRM contract imports a “common” schema as follows:

<xs:schema xmlns:sc="http://schemas.sage.com/sc/2009" xmlns="http://schemas.sage.com/crmErp/2008" 
  xmlns:sme="http://schemas.sage.com/sdata/sme/2007" elementFormDefault="qualified" 
  targetNamespace="http://schemas.sage.com/crmErp/2008" id="crmErp" xmlns:xs="http://www.w3.org/2001/XMLSchema">
**  <xs:import schemaLocation="$schema/common" namespace="http://schemas.sage.com/sc/2009"/>
**
  <xs:element sme:role="resourceKind" sme:pluralName="tradingAccounts" sme:compliance="must" sme:canGet="true" sme:canPut="true" 
    sme:canPost="true" sme:canDelete="true" sme:isSyncSource="true" sme:isSyncTarget="true" name="tradingAccount" type="tradingAccount--type"/>
  <!-- more element and type definitions -->
</xs/schema>

If the imported schema is intended to be shared, as in the example above, it should have its own namespace and it should be imported with an <import> directive, as in the example above.

If, on the other hand, the smaller schema is only a fragment of the larger schema and is not intended to be shared, then it should be included with an <include> directive. The previous example could be modified to include its resource kind definitions from schema fragments, as follows:

<xs:schema xmlns:sc="http://schemas.sage.com/sc/2009" xmlns="http://schemas.sage.com/crmErp/2008" 
  xmlns:sme="http://schemas.sage.com/sdata/sme/2007" elementFormDefault="qualified" 
  targetNamespace="http://schemas.sage.com/crmErp/2008" id="crmErp" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:import schemaLocation="$schema/common" namespace="http://schemas.sage.com/sc/2009"/>
**  <xs:include schemaLocation="$schema/tradingAccount"/>**
**  <xs:include schemaLocation="$schema/contact"/>**
**  <xs:include schemaLocation="$schema/contactGroup"/>
**  <!-- more RK include directives -->
</xs/schema>

SData providers MAY use this feature for large schemas