# Filtering By Namespace

When you expect XML messages with elements that use namespace prefixes, you can use a variable of the Namespace type to query the XML for elements contained in a specified namespace.

The syntax for declaring a Namespace variable is as follows:

> var nsVariable = new Namespace("uriString");

The uriString value is the URI that uniquely identifies the namespace. By associating the variable with the namespace URI, you can then use the variable as you might use a namespace prefix. The syntax for using the namespace variable can be one of the following two variations. The first uses the . operator to separate elements in the hierarchy, which the second uses square brackets.

> value = nsVariable::elementName1.nsVariable::elementName2;

> value = ["nsVariable:elementName1"]["nsVariable:elementName2"];

The second variation is especially useful in cases where the element name conflicts with a script keyword (such as if or return). For more information about working around such conflicts, see A Few Things to Remember About XML Maps and Script.

In the following example, the "http://openuri.org/" namespace is associated with the myco variable.

    /* Declare an XML variable with a literal XML value. */
    var xmlEmps = <employeeData>
        <inc:employees xmlns:inc="http://openuri.org/">
            <inc:employee inc:id="111111111">
                <inc:name>John</inc:name>
                <inc:age>25</inc:age>
            </inc:employee>
        </inc:employees>
    </employeeData>;

    /*
     * Declare a namespace variable to represent the namespace in the document
     * above. When accessing the XML, the myco variable will correspond to the
     * namespace URI in the way that the "inc" prefix above corresponds to the
     * namespace in the XML instance.
     */
    var myco = new Namespace("http://openuri.org/");

    /*
     * Create a new variable to hold the <employee> element containing John.
     * Access the elements by using the namespace variable
     * in double-colons in place of the prefix-colon combination used
     * in the XML literal above.
     */
    var xmlName = xmlEmps.myco::employees.myco::employee[0];

Note that you can also access namespaced attributes in the same way. In other words, you can use @inc::id to access the inc:id attribute in the example, as shown here:

    /* Create a new variable to hold the <employee> node containing John. */
    var xmlName = xmlEmps.myco::employee.attribute(@inc::id);

Or like this:

    var xmlName = xmlEmps.myco::employee.@inc::id;

Related Topics

Accessing Attributes With the @ Operator

Accessing Element Children With the . Operator