into a knowledge warehouse (KW) for which we give
our definition and architecture. Our suggestions rely
on several works of the literature (Kerschberg, 2001),
(Dymond, 2002), (Nemati et al., 2002), (Qing-lan and
Zhi-jun, 2009) and (Irfan and uddin Shaikh, 2010)
that have tried to introduce the KW concept and pro-
pose a basic architecture for a KW. However, these
authors did not provide a precise definition of a KW
and did not detailed its architecture. Indeed, in their
works, a KW is considered as a data warehouse (Dy-
mond, 2002) (Nemati et al., 2002) described with
three layers: capture, storage and access to content.
For example, (Dymond, 2002) considers that the stor-
age structure is referred to as a knowledge base and
is constructed as a tree with objects at the nodes. Ob-
jects are packages containing data in ”attributes” and
blocks of program code in ”methods”.
In addition, most of proposed architectures are
presented in an abstract way and are composed of
three layers (Data source layer, Knowledge manage-
ment layer and Knowledge presentation layer) (Ker-
schberg, 2001) (Dymond, 2002) (Nemati et al., 2002)
(Irfan and uddin Shaikh, 2010). These architectures i)
do not present the interaction between decision mak-
ers and the KW (i.e., How to exploit and update stored
knowledge?) and ii) do not specify the sources of
knowledge: are they exist in business sources of com-
panies, are they extracted from existing data or are
they acquired through the formulation of tacit knowl-
edge from individuals working in these companies.
Furthermore, in the absence of a complete defini-
tion of KW, we rely on the following extracts so that
we can give our definition of a KW:
• The knowledge can be found in multiple repos-
itories under multiple heterogeneous representa-
tion (Kerschberg, 2001) such as databases, docu-
ments, computer programs and even in people’s
heads (Dymond, 2002);
• The knowledge extracted and stored in the KW
should be explicit (Kerschberg, 2001) (Nemati
et al., 2002), i.e., formal and systematic in order to
be easily communicated and shared (Nonaka and
Takeuchi, 1995);
• The KW can be used as a clearinghouse of knowl-
edge to be used throughout the organization by the
employees to support their knowledge intensive
decision-making activities (Nemati et al., 2002).
Based on these three extracts that we consider
incomplete and often reflecting a particular view-
point, we provide our definition. In our viewpoint,
a Knowledge Warehouse gathers explicit knowledge
that may come from multiple sources having heteroge-
neous formats and relating to several business activ-
ities within a domain. This knowledge is unified and
integrated in order to support an intelligent decision-
making process (Ayadi et al., 2013).
Based on this definition, we draw multi-layer core
architecture for a KW (cf., Figure 1). In this archi-
tecture, we find the following tasks located at three
layers (Ayadi et al., 2013).
Data Acquisition: This step is interested in col-
lecting the initial data from companies belonging to
one or more sectors.
Knowledge Extraction: Extracts the hidden
knowledge from the initial data by using multiple
knowledge extraction techniques such as data mining
techniques (Zaki and Meira, 2014).
Tacit Knowledge Explicitness: This step provides
experts with knowledge models to express their tacit
knowledge into explicit knowledge in order to be used
by a computerized decision process.
Knowledge Harmonization: The harmonization
aims to standardize knowledge expressed in hetero-
geneous formats before being loaded into the KW. It
is based on a transformation process that transforms
knowledge from a source model into a common tar-
get model (i.e., MOT).
Knowledge Storage: Storing knowledge accord-
ing to a KW model is crucial for the computerized
decision process. Naturally, stored knowledge could
be later updated by the KW administrator in order to
manage knowledge evolution over time.
Knowledge Exploitation: Once the KW is loaded,
the usage of its content is the ultimate step for intelli-
gently solving decision problems.
As a further step in the KW life cycle is the KW
maintenance. After a decision was taken and evalu-
ated, if the decision maker is satisfied then he vali-
dates it, otherwise he can inform the KW administra-
tor to update knowledge that led to invalid decisions.
In the remaining of this paper, we focus on
the knowledge harmonization as a keystone task for
knowledge warehousing. Knowledge has often sev-
eral representation forms: tacit knowledge of experts
or knowledge extracted through data mining tech-
niques. For this reason, we elected the MOT language
as a unified language for knowledge representation.
3 KNOWLEDGE
REPRESENTATIONS
In the literature, there are several languages for repre-
senting knowledge (Fensel et al., 1994): i) the infor-
mal language allows knowledge explicitness in form
of sentences, their specifications contain ambiguity
and contradictions and lack precision, ii) the formal
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