Information Technology Reference
In-Depth Information
«CV_Object»
User
Operations
«CV_OperationInterface»
iUser2Corporation
«CV_OperationInterfaceSignature»
IUserMgmt
«CV_Object»
Corporation
DataMgmt
«CV_OperationInterface»
iCorporationMgmt
FIGURE 4.1: The concepts involved in connecting computational objects.
share the same signature specification, IUserMgmt), but with complementary
causalities, reflecting their client and server roles.
UML (enhanced with the appropriate stereotypes defined by UML4ODP)
provides a natural and faithful representation of the computational language
concepts. Thus, UML components can be used directly to represent compu-
tational objects, their interfaces and the signature of their operations. UML
components represent computational object types, UML ports are used to
represent ODP interface types, and UML interfaces represent the signatures
of computational signals and operations.
UML is not the only way to specify the interfaces of computational ob-
jects in a platform-independent way | that is, without committing to a par-
ticular programming language or implementation technology. For example,
CORBA [31] is a specification from the OMG that, amongst other things, pro-
vides a platform-independent language to describe object interfaces. This lan-
guage, called CORBA IDL (Interface Definition Language) was also adopted
as standard ISO 14750 [12] as part of the RM-ODP family. It offers a textual
notation for specifying object interfaces and operation signatures. Therefore,
if you take an ODP computational specification, it is not that hard to create
a mapping onto CORBA. ITU-T has another interface definition language,
called eODL (ITU-T Rec. Z.130, ITU object definition language [26]), which
provides some facilities additional to those in OMG's IDL. In the realm of
service-oriented architectures, the interfaces used to represent web services are
specified using WSDL [100]. This can be considered as a specialized version
of an interface definition language for web-based services, which also allows
expression of the ODP computational language concepts in a textual man-
ner. It is therefore also relatively straightforward to create a mapping from a
computational specification to a web service specification.
The ability to specify interfaces precisely is extremely valuable. In the
first place, it allows users and other IT systems to exploit a specification that
describes both the services provided by our computational objects and the
way they should be invoked. These technical services can then be exposed as
discussed in section 1.5. In the second place, service descriptions can be used
