Semantic Composition of Web Portal Components - End User Computing Challenges and Technologies: Emerging Tools and Applications - page 181

and takes into account both the types of users
working with the system and the environment
it is being applied to. CDF examines a subject
system with respect to 13 orthogonal concerns,
that is, cognitive dimensions. We will now iterate
through these concerns, describe them briefly, and
use them to compare our approach to semantic
Web portal composition with the traditional way
of composing WPC components.

• Closeness of mapping: Closeness of rep-

resentation to domain. In the traditional
approach to portal composition, WPCs are
the only abstractions that map close to the
problem domain of the end user. For example,
our case study contains WPCs for assessment
reports, surgical reports, and so forth. Event
interfaces, an important abstraction when it
comes to portal composition, do not closely
map to any end-user domain, posing sig-
nificant cognitive load for portal composers.
In our approach, WPCs and PDO concepts
directly map to the end-user domain. Users do
not directly have to deal with event interfaces
during composition, reducing their cognitive
load.

• Abstraction gradient: What are the mini-

mum and maximum levels of abstraction?

The traditional approach to composing Web
portals uses three main kinds of abstrac-
tions: WPCs, WPC event interfaces, and
portal pages. There are six different types
of WPC event interfaces, namely primitive
sinks, primitive sources, tuple sinks, tuple
sources, relation sinks, and relation sources
(cf. Figure 2). The only way new abstractions
can be defined is by adding new WPCs to
the component library. However, this is a
complex activity, which involves a deep
understanding of low-level programming
techniques in the component framework
architecture used (e.g., ASP.net, C#, MSQL,
and SharePoint). This type of programming
is not realistically considered doable for
end users. Therefore, we may consider the
number of abstractions in the traditional
approach as fixed from the point of view of
the end user. In our semantic composition
approach, three kinds of abstractions exist:
WPCs, portal pages, and domain concepts
(defined within the PDO). Users can easily
define new domain concepts by extending
the PDO (e.g., using ezOwl). Users do not
need to understand the different kinds of event
interfaces. In particular, they do not have to
worry about their directionality in terms of
sources and sinks. WPC interface connec-
tions are generated automatically based on
the user configuring domain instances in the
CIM. Consequently, abstraction is higher
and more extensible in our approach.

• Consistency: Degree to which parts of

the language can be inferred from other
parts.

In traditional portal composition, there
is a cognitive gap between the domain of
WPCs (the end user's problem domain)
and the domain of WPC interfaces (tech-
nical domain of event-based systems and
data structures). This gap does not exist in
the semantic composition approach. Users
use the same concepts in the PDO as well
as in the CIM. They stay on the level of the
problem domain throughout the composition
process. Therefore, the semantic approach to
composition is more consistent.

• Diffuseness : Number of symbols or graphical

entities required to express the meaning.

The newly proposed semantic approach
to composition is more diffuse since it uses
additional graphical entities PDO concepts,
instances of PDO concepts in the CIM. Still,
all of these concepts map closely to the end
user's domain knowledge. Therefore, we do
not believe that this is a significant disad-
vantage.

• Error-proneness: How likely are careless

mistakes?

In the traditional approach, WPC interfaces
are not semantically typed; for example, any