Semantic Composition of Web Portal Components - End User Computing Challenges and Technologies: Emerging Tools and Applications - page 173

Figure 3. Semantic WPC composition: Over-
view

components chosen for the page. The information
provided in the CIM is sufficient for the portal
framework in order to generate the actual event
connections between WPC interfaces.
The following subsections will provide a more
detailed explanation of the approach sketched in
this overview.

portal

Specify/Evolve Portal
Domain Ontology (PDO)

Develop/Evolve
Common Functionality

portal domain ontology

Administrator

An ontology is a predefined set of concepts, re-
lationships among concepts, and constraints on
those concepts that exist in a particular domain.
Ontological specifications are meant to be shared.
Their key benefit is to provide a common under-
standing and terminology for domains. Research-
ers and practitioners in the general area of knowledge
engineering and specific disciplines, such as biology
and medicine, have been using ontologies for many
years. More recently, ontology engineering has
increasingly been applied to software engineering,
in particular for the purpose of business-to-busi-
ness (B2B) data integration and the Semantic Web
(McGuinnes, Fikes, Hendler, & Stein, 2002).
Many languages have been proposed for the
formal specification of ontologies. In the areas of
software engineering, W3C's standards proposal
for the Ontology Web Language (OWL) arguably
seems to have the best chances to achieve broad
adoption (Heflin, 2004). The native representation
of OWL specifications is textual, based on RDF
(Resource Description Format) and XML. Such
textual specifications are hard to comprehend and
maintain. Therefore, our framework uses a graphi-
cal ontology development tool, ezOWL, which
is based on Protege 2000 (Noy, Sintek, Decker,
Crubezy, Fegerson, & Musen, 2001).
Figure 4 shows a simplified excerpt of a PDO
for vision care, which could be used in a portal
associated with a hospital department. Central
conceptual abstractions are entities (e.g., persons,
places, organisations, etc.), acts (e.g., observations,
procedures), roles (e.g., nurses, patients), and
clinical documents (e.g., cataract assessment,

Add/Type WPCs to
Library

Specify/Confirm
Context Information Model
(CIM)

Delete Pages

«extends»

Use Pages

User

Compose Pages

end-user-based WPC composition. In a nutshell,
we employ a formal specification of the concepts
in the application domain served by a particular
portal, a so-called Portal Domain Ontology (PDO).
The PDO is maintained by the portal administrator,
in addition to normal activities, such as granting
privileges for access control, maintaining WPC
libraries, and evolving general portal functional-
ity. Whenever the administrator adds WPCs to a
1ibrary, the administrator ensures that their event
interfaces are semantically typed; that is, they
must be mapped to concepts in the PDO.
With this semantic knowledge about WPC
component interfaces, the portal can provide end
users with a simpler, more abstract composition
paradigm, namely a paradigm that is grounded in
the user's business domain. Composing portal pages
in this new paradigm happens in two steps: first,
the user selects the components to be presented on
the page, and, second, the user associates a Context
Information Model (CIM) with the composed portal
page. Essentially, the CIM contains instances of the
concepts in the PDO and relates them to the WPC