Information Technology Reference
In-Depth Information
communicated to composite services. If a composite service does not receive State
i
after a certain period of time, then it assumes a physical fault or status change in WS
i
.
Otherwise, the composite service reads State
i
to find out about the changes made to
WS
i
.
Fig 2.
State of a Participant Service
A policy
category
refers to the type of requirements specified by a policy. As
mentioned in Section 2.1, it refers to functional, non-functional, value-added, or do-
main (i.e., vertical) categories. Policies are specified in XML-based Web service
languages/standards (e.g., WSDL [1], WS-Security [14]). The
scope
of a change
defines the subject to which that change was applied. It includes details about (i) the
location of the modified policy specification and (ii) the element that has been up-
dated within that specification. The specification location is given by the URI of the
XML file that stores the specification. The updated element is identified by the XPath
query of that element within the specification. For instance, let us consider the fol-
lowing WSDL file located in “http://www.ws.com/sq.wsdl”:
<definitions>
<types> <!-- XML Schema --> </types>
<message name=“getQuote_In”> ….
<message name=“getQuote_Out”> …
<portType name=“StockQuoteServiceInterface”>
<operation name=“getQuote”>
<input message=“getQuote_In” />
<output message=“getQuote_Out” />
</operation>
</portType>
...
Let us assume that the name of the operation "getQuote" has been modified in the
WSDL document. The category and scope of the change are defined as follows:
•
Category = (Functional,WSDL).
•
Scope = (URL,Q) where:
•
URL = “http://www.ws.com/stockquote.wsdl”
•
Q = “definitions/portType/operation/@name”
The following definition summarizes the properties of State
i
maintained by a par-
ticipant WS
i
.
