Defining Namespaces

A namespace uniquely identifies a Web service and is specified by the <targetNamespace> element in the WSDL that represents the service. A data service is simply a Web service with specialized functionality. As a data service implementation is based on XML, namespace handling is an important aspect to it. 

When developing a data service, you get to specify namespaces in several places as follows:

Service namespace

The service namespace is used to uniquely identify a web service. In the WSDL which represents the service, it is indicated by the "targetNamespace" attribute of the WSDL document element. The service namespace can be set using the  Create/Edit Data Service window of the Data Services Server management console.

For example,

Data service result row namespace

This namespace is set through the Row namespace value in the query result section. It associates the result rows or result entries of a specific namespace. Therefore, all the subelements in that result raw are under this namespace by default.

The example below shows how the row namespace is set for the query result element: Customers .

After setting the row namespace, the Customers element's data type falls under the given namespace.

The XML Schema fragment in data types section taken from the service's WSDL is as follows:

Namespaces for specific elements in the result

You might want only selected elements in the result row to contain a specific namespace. This can be defined by setting the namespace in the output mappings as follows:

This is how the setting is reflected in the WSDL.

Namespaces for complex results

In complex results in data services, the result elements can be arbitrarily nested. These nested elements can have their own namespaces. The example below shows how this is represented in a database file fragment, which has a complex result.

<query id="customersInBostonSQL" useConfig="default">
      <sql>select  * from Customers where city = 'Boston' and country = 'USA'</sql>
      <result defaultNamespace="http://abc.com/nsb" element="customers" rowName="customer">
         <element column="customerName" name="customer-name" xsdType="string"/>
         <element namespace="http://abc.com/nsb" name="contact">
         	<element column="contactLastName" name="contact-last-name" xsdType="string"/>
         	<element column="contactFirstName" name="contact-first-name" xsdType="string"/>
         </element>
         <element column="phone" name="phone" xsdType="string"/>
         <element column="city" name="city" xsdType="string"/>
         <element column="country" name="country" xsdType="string"/>
      </result>
</query>

The WSDL created for the above service is as follows:

The resulted XML of the executed service is as follows:

Namespace inheritance in a data service

There's an inheritance order where a top-level namespace is inherited by its children. In summary, the inheritance is as follows:

• Service namespace is applied to all aspects of the data service, i.e. results.
• Result row namespace overrides the service namespace and applies a given namespace for the whole result.
• Complex result, nested elements override the result row namespace and assign the namespace to all its child elements.
• A namespace specifically assigned to an element overrides the parent element's namespace and assigns the given namespace to itself.