For
instance, the month of a sale could be obtained as month(date). (b) Aggregation:
tells if the aggregated data is or is not present in the source, or can be
computed from the data in the source. (c) Accuracy. (d) Timeliness. The last
two dimensions apply to our case study, but can be replaced by a different set
of dimensions if the problem at hand requires it. In our case study, the record
tells that for query Q2, data element
sales can be obtained from data source B (where it is in nonaggregated form),
with 70% accuracy and with a timeliness of 5 minutes.
??? Data.source.quality.(consistency):.The form DS_QTY_II is completed, with
the consistency characteristics of the data source. There is one entry for each
data source, containing an evaluation of the source??™s consistency. In our case
study, consistency condition Q2C above is accomplished with a 100% precision
by data source A, and 90% precision by data source B.
??? Data.source.quality.(completeness): The form DS_QTY_III is filled analogously
to form DS_QTY_II, addressing completeness instead of consistency.
In our case study, the completeness condition stating that all customers regis-
80 Vaisman
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