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Again welcome to ITSE2309
Chapter 4 brings togeter ideas we have talked about that we have introduced in chapters two and three
the idea of the 'Primary Key" and the ability to connect data
as it is broken down into smaller more manageable pieces
and how relationships in data can be graphically represented
with the concepts of Chan and Crow's foot
so the question is
how can you graphilly differentiate between
a relationship
that has one too many
such as
you have many cars
and the need to state that you can only drive one car at a time
also
how do you reconcile the idea of how pure data must be
the quality of data
back to the credit card scenario for a moment - when a credit card company mails
out the monthly billing statement
does my name have to be spelled correctly on the address label
for the bill to reach my address
or does the address have to be correct
on the billing statement
for the biling statement to reach my address
it is easy to determine that dependng on a particular situation
some data can be more significant than other data
as data is related amongst itself
such as the mailing label and the monthly statement -- now
when I receive my statement
if my name is not spelled right on the statement
do I still have to pay it
or
does some other primary identifier such as the account take priority over the actual billling payment structure
Chapter 4 introduceds new terms , new concepts ,new terminology
to assist with the management of these ideas
this concludes module four