acid policy assertions proposal

[Greg Pavlik <greg.pavlik@oracle.com>]

Policy Assertions


Web services endpoints that support the ACID transaction protocol may 
wish to advertise policies indicating their capabilities and 
requirements. This specification defines an assertion indicating that 
the ACID protocol must be used in communication with the service with 
which the policy is associated.

The ACID policy assertion is defined by the following schema, which is 
defined for the target namespace of the acid protocol:

<xsd:element name=”TXAssertion”>

<xsd:complexType>

<xsd:sequence>

<xsd:any namespace=”##other” processContents=”lax” minOccurs=”0” 
maxOccurs=”unbounded”/>

</xsd:sequence>

<xsd:attribute name=”optional” type=”xsd:boolean” use=”optional” />

<xsd:anyAttribute namespace=”##other” processContents=”lax”/>

</xsd:complexType>

</xsd:element>

The assertion mandates that an acid:Context MUST be present as a SOAP 
header on a message sent to the service advertising the policy. A value 
of true for the optional attribute modifies the assertion semantic to 
indicate that an acid:Context MAY be included as a SOAP header when 
submitted as a request. A value of false indicates that an acid:Context 
must be included as a SOAP header on a message sent to the service; it 
is semantically equivalent to the assertion without an optional attribute.


A service that advertises an acid:TXAssertion guarantees to process the 
SOAP header in an implementation specific way. It does not guarantee to 
perform all work performed in the context of the application invocation 
in an ACID transaction. For example, a service may be implemented as an 
EJB or COM+ component that suspends all transactions related to the 
operation of the implementation. In this case, the semantics of the Web 
services interchange are obeyed: the header must be processed, but the 
service does not perform transactional work.

An example of a policy assertion specifying that an acid:Context MUST be 
present on any incoming SOAP requests follows:

<acid:TXAssertion/>

or

<acid:TXAssertion optional=”false”/>

An example of a policy assertion specifying that an acid:Context MAY be 
present on any incoming SOAP requests follows:

<acid:TXAssertion optional=”true”/>

Services can communicate policies in an implementation specific manner. 
The semantics of a service that does not advertise an ACID policy 
assertion are undefined.