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area immediately following in importance the previous one. Obviously, other
criteria could also be used. This is a cyclic process, which results in a final
document containing consistent, nonredundant queries. In addition to the
queries, nonfunctional requirements should also be elicited and specified.
These are criteria that can be used to judge the operation of a system rather
than specific behavior. Thus, a list of nonfunctional requirements may be
associated with each query, for example, required response time and accuracy.
Define Facts, Measures, and Dimensions
In this step, the analyst tries to identify the underlying facts and dimensions
from the queries above. This is typically a manual process. For example, in the
documentation of this step, we can find a query “Name of top five customers
with monthly average sales higher than $1,500.” This query includes the
following data elements: customer name , month ,and sales . We should also
include information about which data elements will be aggregated and the
functions that must be used. If possible, this step should also specify the
granularities required for the measures and information about whether they
are additive, semiadditive, or nonadditive (see Sect. 3.1 ).
Document Requirements Specification
The information obtained in the previous step should be documented.
The documentation delivered is the starting point for the technical and
business metadata (see Sect. 3.4 ). Therefore, this document should include
all elements required by the designers and also a dictionary of the terminology,
organizational structure, policies, and constraints of the business, among
other things. For example, the document could express in business terms what
the candidate measures or dimensions actually represent, who has access to
them, and what operations can be done. Note that this document will not be
final since additional interactions could be necessary during the conceptual
design phase in order to refine or clarify some aspects.
10.3.2 Analysis-Driven Requirements for the
Northwind Case Study
We now apply the analysis-driven approach to produce a requirements
specification for the Northwind data warehouse. We do not include all details
about each step. We limit ourselves to illustrate only the essential aspects of
the method.
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