Information Technology Reference
In-Depth Information
4.3.2 Specifying Data Mapping
The functionality of data mapping is to define rules to relate (syntacti-
cally/semantically equivalent) elements of two messages such that two
interfaces belonging to different services can be linked, and ultimately,
services can be composed. In the specification of BPEL, messages
exchanged between two Web services are modeled as an aggregation
of parts and/or elements. Therefore, data mapping can be performed at
the message, part or element levels.
It is noted that data mapping is a very challenging problem in the
area of data integration, semantic Web, and SOA. We assume that the
data mapping relation between two services to be composed is specified
by service composers who intend to compose them. We then focus on
how to detect the behavior mismatches between two services and how to
build a mediator to glue them (if possible). Semantic Web service
technology allows the semiautomatic and automatic annotation of Web
services, and therefore, can be very helpful in the generation of data
mapping relations between two services. Some prior works [97,116]
focused on the data semantics and transformation between Web service
interfaces. Instead, we focus on the behavior analysis and mediation via
data transformation. Note that the proposed approach can be combined
with the prior ones to provide a total solution to more adaptive and
semantic-enhanced Web service composition.
Data mapping I between N 1 and N 2 is a finite set of data mapping
rules. Each rule is expressed in the form of
,
where src can be a message, a part or element of a message whose
place is with the polarity of
<
src, target, trans_flag
>
1 (i.e., an outgoing message place); src
can also be a constant. target can be a message, a part or element of
a message whose place is with the polarity of
1 (i.e., an incoming
one). trans_flag is a Boolean variable and the default value is false.
It is set to be false if target can be mapped from src directly, and it is
set to be true if target can be mapped from src with additional
transformation.
The data mapping may enjoy the following properties:
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Completeness. Every element/part of a target message appears on
the right-hand side of some mapping rule.
Accuracy. Every element/part of a target message appears in at
most one right-hand side of a mapping rule.
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