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lost, tossed, outdated, and/or not maintainable.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