Location: [CPSC 333] [Assignments] [More about Problem to Model for Question #1 on Assignment #2]
Question:
I do not exactly understand how the ``next transaction numbers'' for the various accounts (of which I assume there can be arbitrarily many) can be stored in a register. Can this be changed to an attribute of account?
Answer:
Yes, you're absolutely right.
Since there can be arbitrarily many accounts, there can be arbitrarily many versions of the ``next transaction number'' for this system to keep track of - too much to go into one register, and we don't want there to be ``arbitrarily many'' data stores on the DFD (corresponding to ``arbitrarily many'' registers).
I've updated my data dictionary, by adding a non-key attribute for Account that's called ``next transaction number,'' and adding a definition for this as an integer.
The user won't need to specify this when the account is created - its value will be set to 1 automatically. It doesn't need to be displayed on any reports, and the user can't reset its value (instead, it's automatically incremented, every time a new transaction for the account is created).
Now, groups who do show extra data stores for this will be doing something that's a bit nonsensical, but they'll also probably be doing something that's reasonable, considering the mistake made in the specifications (which I've just corrected). Either no penalty will be made for this at all, or it will be tiny (at most 2% of the total value of the assignment).