Using Namespaces

Data services are implemented using XML, which means that there can be conflicting element names. Therefore, we use namespaces to uniquely identify the elements defined within a specific web service. Using namespaces for a data service is optional. However, in certain data services, namespaces become necessary. Read below for more information.

Namespace inheritance in a data service

Namespaces can be defined at different levels of a data service, which means that you can have multiple namespaces applicable to your data service at the same time. In such a scenario, the top-level namespaces will be inherited by the lower level as explained below.

  1. The namespace at the data service level applies to all aspects of the data service, i.e., to all elements in the results of all the queries (output mapping).
  2. The namespace at the query result level (row namespace) overrides the service namespace and applies a given namespace to all the result elements (output mapping elements) of that query.
  3. The namespace specified for a result element (output mapping) overrides the query-level row namespace.
  4. If you have a complex element with child elements nested :
    1. The namespace for the complex element overrides the result row namespace and assigns the namespace to all its child elements.
    2. The namespace specifically assigned to a child element overrides the parent element's namespace.

See the following topics for instructions on setting namespaces at different levels of a data service:

Setting the namespace for a data service

The service namespace is used to uniquely identify a web service, which means that this namespace applies to all elements in the data service. In the WSDL that represents the service, the namespace is indicated by the "targetNamespace" attribute.

Setting the namespace for a data service query

When you define a query for your data service, you can set a namespace for the elements in the query result (output mapping). That is, the Row Namespace applies to all the result rows that you define as output mappings for that query. For example, the row namespace can be set for the query result element: Customers .

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

Info

If you have multiple queries with the same element wrapper but different element rows, be sure to use separate namespaces for each query. The example below illustrates two queries in a data service (.dbs file) with the following qualities:

  • The element wrapper is the same for both queries, which is <result element="employees" rowName="employee"> .
  • The two queries contain two unique element rows: ' salary ' and ' phone '.

Therefore, since we are using the same element wrapper for both queries, we need to use two separate namespaces to identify the two conflicting elements ('salary' and 'phone') in the two queries as shown below.

<query id="employeesByNumberSQL" useConfig="default">
      <sql>select * from Employees where employeeNumber = ?</sql>
      <result defaultNamespace="http://abc.com/empNamespace1" element="employees" rowName="employee">
         <element column="lastName" name="last-name" xsdType="string"/>
         <element column="firstName" name="first-name" xsdType="string"/>
         <element column="email" name="email" xsdType="string"/>
         <element column="salary" name="salary" xsdType="double"/>
      </result>
      <param name="employeeNumber" ordinal="1" sqlType="INTEGER"/>
</query>
<query id="employeesByIDSQL" useConfig="default">
      <sql>select * from Employees where employeesID = ?</sql>
      <result defaultNamespace="http://abc.com/empNamespace2" element="employees" rowName="employee">
         <element column="lastName" name="last-name" xsdType="string"/>
         <element column="firstName" name="first-name" xsdType="string"/>
         <element column="email" name="email" xsdType="string"/>
         <element column="phone" name="phone" xsdType="string"/>
      </result>
      <param name="employeeID" ordinal="1" sqlType="INTEGER"/>
</query>

Setting namespaces for specific elements in the query result

The row namespace applies to all elements in the query result. Alternatively, you can specify namespaces for selected elements (output mapping elements) in the query result as shown below.

Info

If you have a data service query using the same result element multiple times, be sure to use separate namespaces for each element to avoid conflicts. The example below illustrates a single query in a data service (.dbs file) that has the same element defined twice. In this situation, we have to use separate namespaces for the two elements in order to distinguish them separately. 

<query id="getProductByIDSQL" useConfig="default">
      <sql>select * from Products where productID = ?</sql>
      <result defaultNamespace="http://abc.com/productIDNamespace" element="products" rowName="product">
         <element column="productID" name="productID" xsdType="string"/>
         <element column="productID" name="productID" xsdType="INTEGER"/>
         <element column="productName" name="productName" xsdType="string"/>
      </result>
</query>

Setting namespaces for complex results

In complex results, the result elements can be arbitrarily nested. These nested elements can have their own namespaces. The example given below illustrates a query with a complex result (nested elements). As shown below, the namespace specified for the 'contact' element is inherited by the child elements that are nested within. However, if you assign specific namespaces to the child elements, the namespace inherited by the parent element will be overridden.

<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>
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