Humans are very good at context-specific interpretation of information; computers are not.
Humans can reinterpret and correct misunderstandings and miscommunications, whereas computers typically cannot.
This is a critical distinction when you realize that terminology is the basis for modeling.
Here is a simple example of how critical it is to define project terminology.
In the course project, where you are developing an online ticket sales system for a local auditorium, the word "hold"
can have a variety of possible definitions:
Change the status of a seat while a customer decides whether or not to buy it
Lock the database record
File a ticket at the door for pick-up
Suspend a transaction
Keep the ticket and do not mail it because a payment bounced
How can you resolve these conflicting definitions?
To resolve conflicts over the interpretation of words in everyday situations,
you can pull a dictionary from the shelf and get the definition of the term in question.
In a project, you can create your own dictionary. A data dictionary defines the vocabulary of the problem domain.
Entries in the data dictionary can and will change over the course of a project,
but they should change only when everyone involved in the project agrees to the change.
Use a data dictionary to ensure consistent, high-quality communication.
What belongs in a data dictionary? The examples below will give you a good starting point.
For nouns, you should include these items:
| Name :
||Fully qualify the name with adjectives if needed to distinguish the term as applied in different contexts
|| Allow multiple definitions only when each context is clearly defined
||Other terms that may be encountered during the project and that mean the same thing
|| What kind of data is used to describe this element?
||How many characters or digits are allowed?
||What field names hold this information in the old systems or in related systems
|Example of its use:
||Provide an example of how the users might refer to this item in conversation
||Is this element derived from other information? If yes, then specify the derivation rule.
Click the Exercise link below to identify key data dictionary nouns in the course project problem statement.
Data Dictionary - Exercise