AI 18 - Usage of wsrp:dialect

[Peter Niblett <peter_niblett@uk.ibm.com>]

wsrp:dialect appears as an attribute in the wsrp:QueryExpressionType. This
type is currently used in BaseNotification for the precondition and
selector that appear as Subscription properties and in the subscribe
message.

wsrp:QueryExpressionType has the following definition

  <xsd:complexType name="QueryExpressionType">
    <xsd:sequence>
      <xsd:any minOccurs="1" maxOccurs="1" processContents="lax" />
    </xsd:sequence>
    <xsd:attribute name="dialect" type="xsd:anyURI" />
  </xsd:complexType>

The rationale for reusing the type is

1. The syntax provides what we need for Selector and Precondition
2. There's a close similarity between the semantics of the Precondition
element/property and the wsrp:QueryExpression, and a reasonable similarity
with the semantics of the Selector. Using a common schema type definition
emphasises this similarity.
3. It means that there is one fewer type definition out there

On the other side of the balance it should be noted that

a). This is now the only dependency that the BaseNotification xsd has on
the Resource Properties namespace
b)  TopicExpressions (which are also dialected) use a TopicExpressionType
which is defined in a WS-Notification namespace, and doesn't use the wsrp
namespace.

Peter Niblett