(Timeliness and accuracy
apply to our case study, other cases may require different quality dimensions).
The other two forms, QRY_QTY II and QRY_QTY III, specify consistency
and completeness requirements respectively.
6 Vaisman
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Example.2:.In our case study, in the form QRY_USR, the entry for query
Q2, informed by user U5 (George Martinez) reads: ???Top 50 customers,
among the customers with monthly average sales higher than $1500.???
This query includes the following data elements: D1 (sales), D4 (month),
D5 (customer name), D7 (year), and D13 (customerId). For each of these
elements, there is an entry in form QRY_QTY1. For instance,
sales, NO, -, high, 10>, meaning that in query Q2, data element D1, representing
sales, will not be used to aggregate, requires a ???high??? value for
timeliness, and a minimum accuracy of 10% (i.e., maximum accepted
divergence between data and real world value). Analogously, form QRY_
QTYII contains the consistency conditions for data D5 in query Q2. The
condition ID is Q2C, and the description is ???the best customers must be
the ones classified as ???international.??™ ??? For D5, consistency is mandatory.
The form QRY_QTYIII records completeness conditions for data element
D5 in query Q2.
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