These entities of the knowledge base also have their
properties assigned. While the properties used can
differ from concept to concept, generally they all
include a name and description property. Following
the previous example, the property “description” of
the measure contains a general description of this
measure allowing other actors to better understand
its meaning. Furthermore, the property “literature”
of a measure can contain bibliographic content
pointing to literature with comprising and detailed
definition of the measure. If a measure is derived
from other measures, the property calculation rule
contains the rule by which this measure is derived
from others. Beyond that, the source property of a
measure provides information about the source
systems from which a specific measure can be
obtained.
The concepts cube and measure instance
depicted in the MD requirements meta model (figure
3) are relevant for representing specific information
needs contained in the MD requirements models.
The MD requirements models each link to a specific
part of the knowledge base according to the specific
information needs they represent. While the
knowledge base comprises the general knowledge
about multidimensional business problems within
different business domains, the specific information
needs of business professionals constitute a partition
of the whole knowledge base. By determining the
information needs, measures are instantiated with
specific dimensions and levels. As for example the
measure “actual working time” has the potential
dimension levels “minute”, “hour”, “day” up to
“year” stored in the knowledge base, a specific
information need comprises relevant dimension
levels on a more aggregated level from “day” up to
“year” neglecting the more granular levels. To allow
this the measure instance concept links between the
general measure and a specific dimension level at
which it is measured.
4.3 Core Functions
The system offers three core functions providing the
interaction of the actors with the system: the
management of the knowledge base, the selection of
requirement specific measures and the generation of
a platform independent model from the knowledge
base and the specific requirements.
The management component allows domain
experts to access the knowledge base and to create,
edit and delete respective entities. The domain
experts are able to define functions, measures,
dimensions and dimension levels and to specify the
respective properties such as name, description,
calculation rule, literature source etc.
Based on the knowledge stored in the knowledge
base, business professionals can select measures,
dimensions and dimension levels to define and
formulate their multidimensional business problem,
resulting the specific MD requirements models The
process of formulating multidimensional business
problems is facilitated by selecting relevant
measures and determining the needed level and
hence the business professional creates the MD
requirements model, which can be seen as a CIM
according to the MDA introduced in chapter 2.1.
Based on the MD requirements model and
further information available in the knowledge base,
a multidimensional platform independent model
(MD PIM) based on ADAPTed UML (Priebe and
Pernul, 2001) is generated. This model can then be
used by IT professionals for further development of
the DW.
4.4 Implementation Detail
The system architecture described is realized as a
web application created using Java technologies. In
the prototype the raw data managed in the repository
is saved in a graph database Neo4j (Neo Technology
inc., www. neo4j.org/) since the interconnected
concepts in the domain and requirements model
suggest that form of storage. Furthermore Neo4j
offers a simple and clearly defined API, allowing the
wrapping of nodes directly to java objects. The
different components of the system can then work
on those objects without having any knowledge of
the underlying persistence layer. The inference
mechanisms needed by the selection and generation
components are achieved by extending the java
objects, i.e. adding new methods that will support
the inference based on the underlying graph nodes
and relations. For example the measure instance
“actual working time” gathered at the level “day” is
also available at all aggregated levels such as
“week”, “month” and “year” which are inferred by
the method. In the database the node representing
the measure instance “actual working time”
specified at the level “day” is only connected to the
node of the dimension level “day”. By traversing the
graph the system can then infer the other dimension
levels available for the measure.
The representation on the client side is achieved
by different dynamic pages. They allow users to
access the management functionality of the
knowledge base as well as the selection and
generation component.
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