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changes into the data warehouse. The ear-
lier version is called parent version and the
derived version is called child version. As
soon as a new version is created, a label
is assigned to it and relationship is created
between them [parent and child version].
department, program, time, employees and
university_fact] can be shared with parent
version.
Data Sharing: in order to reduce data re-
dundancy in the presence of versions of
the data warehouse, data is shared amongst
tables from different versions. According
to this approach, single instance of data is
stored at physical level and shared by dif-
ferent tables at logical level. This is done
by attaching a bitmap to each record of
table for each data warehouse version
(Bebel, 2004). The value of bitmap could
be 1 or 0.
Reconfigure ETL: due to changes in di-
mension and fact tables, often the ETL
component may not be able of extracting,
transforming and loading the data into the
data warehouse. Therefore, it is required to
reconfigure ETL to fulfill demands of new
versions of the data warehouse. For ex-
ample, if “comprehensive exam” is added
in the requirements of each degree, it is
required to add a new version of the data
warehouse by extending the dimensional
schema in a way that is capable of accom-
modating change in academics. Also, ETL
cannot populate the extended schema (new
Schema adaptation: in this step the di-
mensional schema is upgraded in such a
way that it can handle changes in schema.
This can be done by adding or removing
dimension tables, fact tables, attributes,
levels or relationship etc. Contents before
changes in source are reflected from par-
ent version whereas the contents after the
change are reflected in the new version.
Schema sharing: data warehouse ver-
sions can partially share their schemas
e.g. dimensions tables or fact tables can
be shared between versions. In this step
shared tables are identified by the admin-
istrator. If a table T is evolved as a result
of change, the table T cannot be shared by
parent and child version. Whereas, if table
X doesn't change, the table x can be shared
by parent and child version. For example,
if a course offering is changed it will not
affect the relationship of department and
school. Therefore, the tables [schools,
Figure 5. Change adaptation process
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