Page 241 - DCAP603_DATAWARE_HOUSING_AND_DATAMINING

Unit 12: Metadata and Warehouse Quality

ds : DataStore notes
constraint c :

$ exists qf1,qf2/DataStoreAvailability
t1,t2,t3/TransactionTime v1,v2/Integer
(qf1 onObject ds) and (qf2 onObject ds) and
(this worksOn ds) and (this executedOn t3) and
(qf1 when t1) and (qf2 when t2) and (t1<t2) and

(t1<t3) and (t3<t2) and (qf1 achieved v1) and
(qf2 achieved v2) and (v1 > v2) $
end
The query has a data store as parameter, i.e. the query will return only cleaning processes which
are related to the specified data store. The query returns the processes which have worked on the
specified data store and which were executed between the measurements of quality factors qf1
and qf2, and the measured value of the newer quality factor is lower than the value of the older
quality factor. The query can be formulated in a more generic way to deal with all types of data
warehouse processes but for reasons of simplicity and understandability, we have shown this
more special variant.
Finally, Figure 12.6 shows the trace of a process at the instance level. The process pattern for
DWLoading has been instantiated with a real process, which has been executed on the specified
date “April 15, 1999”. An instantiation of the links to the quality factors is not necessary, because
the information that “data cleaning” affects the accuracy and the availability of a data store is
already recorded in the process pattern shown in Figure 12.5.

figure 12.6: trace of a Data Warehouse process

Task Discuss the architecture of data warehouse with a neat diagram and explain
each component’s functionally in detail.

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