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Is Part Of
Team
Agent 2
R
Goal
P
De
AND
AND
Mitigate Risk
G2
Is Part Of
G1
++ D
++ D
G2
-
De
Risk
-
Agent 1
G1
Fig. 2.
The “Collaboration in Small Groups for Risky Activities” pattern
Fig. 2, the pattern indicates
TEAM delegates execution of G1 to AGENT1
will
match elements that involve two roles, where the first role delegates execution of a goal
to the second role. Moreover, in some patterns (e.g., GoF [2]) pattern contexts are left
implicit and designers need to fill the details. A pattern is applicable to the problem-at-
hand if all constructs in the pattern match corresponding elements of the problem. When
such a match is found, the reasoner returns not only true, but also mappings for pattern
variables. Patterns are formalized in two parts: (i) the
mandatory part
must be matched
in the problem-at-hand for the pattern match to succeed; (ii) the
optional part
can bring
about useful mappings for variables, but do not affect the outcome of a pattern match. In
our approach, matching is performed at the individual level (ABox) of the knowledge
base. Therefore, the reasoner checks for individuals present in the problem and the
relationships among them, and lists all individuals that match the pattern context. Note
that reasoners can return more than one resultset, since it is likely there are several parts
of the model that match a given pattern context.
In the context of security and dependability, the
optional part
is only used to define a
new actor (including its capabilities & responsibilities) that is not necessarily present in
the problem. For instance, A client needs to buy a house from Company A, but he does
not trust Company A. Based on [6], to ensure security, the designers can “patch” the
trust issue by having a contract arranged by a lawyer. However, in most cases the lawyer
does not exist in the “current” statement of the problem, hence the need for optional
elements during a pattern match. Application of the pattern basically introduces, a new
role - lawyer (i.e., a trusted
3
rd
party
).
models can be queried using two languages: SPARQL [12], and SQWRL
[13]. The SPARQL is a W3C Recommendation [12] for querying RDF. RDF essentially
offers directed labeled graph data format, built out of triples. Thus, SPARQL queries are
expressed in terms of triple patterns, consisting of a subject, predicate, and object. The
OWL-
DL
