Database Reference
In-Depth Information
Interview descriptions of processes
■
Diagrams of current systems or databases
■
Notes taken during observation sessions
■
Lists that describe data that is required to meet a regulation
■
Business reports
■
Number estimates, such as sales per day or shipments per hour
■
Use case diagrams
■
This list certainly isn't exhaustive, but it gives you a good idea of what
to look for in the requirements. Keep in mind that some information that
you need to keep may not directly affect the database design, but instead
will be useful for the database implementation. For example, you need in-
formation about data usage, such as how many orders the company han-
dles per day, or how many customers the company has. This type of
information probably won't influence your design, but it will greatly affect
how you pick indexes and plan for data storage.
Also, be on the lookout for irrelevant information; for example, some
information gathered during user interviews doesn't offer any real value.
Not all users provide helpful details when they are asked. To illustrate this
point, here is a funny anecdote courtesy of one of our tech editors. While
working on redesigning an application for a small college, he kept asking,
“How long can a name be?” The reply he received was, “An address label
is four inches wide.” This answer is not wrong, of course, but it's not very
useful. Be very clear with your customers, and guide them toward the an-
swer you need; in this case, ask them how many letters a name can have.
One last note: Keep your eyes open for conflicting data. If you ask
three people about the ordering process and you get three different an-
swers, you may have stumbled upon a process that users do not fully un-
derstand. When this happens, you may need to sit down with the users,
their supervisors, or even upper management and have them decide how
the process should work.
Identifying Superfluous Information
Superfluous information is, by definition, extra or redundant information.
We won't go as far as to call it useless, because it may be useful to other
groups or during other phases of design. Here, you are looking for anything
that doesn't help to further define the data requirements. Anything that
has nothing to do with data, its usage, or relationships can probably be ig-
Search WWH ::
Custom Search