definition for equivalence that is extensional in
nature.
(Xue 2010) presented another framework to
address the data integration in open environment.
The author attempted to address three main issues,
namely; the heterogeneity, the architecture, and the
modeling and representation of ontologies. The
author in (Xue 2010) proposed the use of ontology
and semantic matching to bridge the heterogeneity
gap between various information systems. In (Xue
2010), however, database schemas were used to
extract semantics and to generate ontologies. This
yields a set of data-driven-ontologies (DDO). The
use of DDO is a good idea when an ontology is
missing. However, relying on the schema as a source
of semantics is inadequate. This is because the
semantics embedded in the database schemas are
lost, tossed, outdated, and/or not maintainable.
Moreover, the author in (Xue 2010) employed a
frame-based language (Xue, Ghenniwa, and Shen
2010). It is known that Frame-based languages are
limited in their expressiveness and reasoning. The
semantics of Frame-based languages are also not
precisely defined (Selman and Levesque 1993). The
author in (Xue 2010) also used an extensional
reduction model. It has been shown in (Ali and
Ghenniwa 2012) and (Ali and Ghenniwa 2014) that
the extension reduction model does not address the
needs of an open environment.
And finally, a mediated architecture was adopted
by (Xue 2010). Similar architectures are also utilized
in (Ali and Ghenniwa 2014), (Calvanese et al. 2018)
and (De Giacomo et al. 2018). The mediated
architecture relaxes the requirement that each
information system behaves as a DIS on its own.
This is a constraint that P2P systems (Majkić 2009)
naturally require. On the other hand, the mediated
architecture is centralized and, as such, is not
adequate for open environment.
In this work, a framework for data integration
system is presented. The proposed framework
addresses the issues mentioned above. We will start
by shedding some light on the IEL as the IEL is
important to modeling DIS in open environment.
2 PROPOSITIONAL EPISTEMIC
LOGIC
Epistemic logic is the logic of knowledge and belief.
Even though, epistemic logic and doxastic logic
formalize the knowledge and belief, respectively, the
term epistemic logic is also commonly used to refer
to both the logic of knowledge and the logic of
belief. The main focus of epistemic logic is the
propositional knowledge. That said, an agent bears
the propositional attitude “knowing” or “believing”
towards a proposition. As such, when we say: “Joe
knows that Tom loves Merry” we are asserting that
Joe is an agent who bears the propositional attitude
“knows” towards the proposition expressed by “Tom
loves Merry”.
The syntax of the propositional epistemic logic is
simply the result of augmenting the language of
propositional logic with the unary knowledge or
belief operators K
a
or B
a
; where a is an agent, and
the operators K and B are the epistemic operators for
knowledge and belief respectively. In that sense, if P
is an arbitrary proposition, following is how these
operators are read:
K
a
P reads “Agent a knows that P”
And for the belief operator of doxastic logic:
B
a
P reads “Agent a believes that P”
3 INTENSIONAL EPISTEMIC
LOGIC
As discussed in (Fitting 2006) and (Bealer 1979)
knowledge and beliefs are intensional matters. The
same interpretation is adopted by (Ali and
Ghenniwa 2012) in the context of knowledge
engineering. IEL (Jiang 1993) offers a way to
properly handle relative intensions in nested
believes. The most distinguished feature of the
intensional epistemic logic is the use of intensional
index on the terms. The basic idea is that, given a
formula like B
a
p(b), b does not have to have to be
rigid. That means, b does not have to have the same
meaning everywhere in the formula or same
denotation in all possible worlds. And so, we need
some mean to distinguish the case when b is
evaluated inside the intensional scope of agent a,
and the case when b is evaluated outside the
intensional scope of agent a. to achieve this, a
superscripted index is attached to each term to
denote the number of the believe operator that
contains the intended meaning of the term. If a term
is not attached with an intensional index, then the
intended meaning of the term is rigid. For example;
the formula B
a
(Q B
b
Q), where Q’s intended
meaning is in the scope of B
a
, can be represented in
IEL as B
a
(Q
1
B
b
Q
1
). If the second Q in the original
formula is intended to be local to B
b
, then the