using the entity-relationship model
- Get a feel for the problem
by sketching E-R diagrams.
Don't worry about getting all the details correct
at this point.
- Prepare a preliminary list of functions and transactions
which the model must support.
- Write down a list of entities
and select the key or identifier for each.
- Prepare a list of attributes.
Use attributes that cannot be divided further;
use Last name and First name
rather than Name.
Do not use attributes
that can be derived using other attributes;
for example, Age from Date of birth.
Use single-value attributes,
not multi-value attributes
such as First author, Second author, etc.;
if multi-value attributes occur,
try promoting them to entities.
- Draw an E-R diagram
showing the known relationships between entity classes.
Include maximum cardinality and membership class details.
- Make a preliminary check
that your E-R diagram will support the transactions,
and amend the diagram if necessary.
Assign attributes to entities
- Using the rules
for converting entity-relationship diagrams
to a set of relations,
develop skeleton tables corresponding to your E-R diagram.
- Check off all attributes in your attribute list
that are used in the skeleton table identifiers.
- Add the remaining attributes to appropriate tables
and check them off in the list.
- If there are any attributes left over
which cannot be assigned,
define further entity classes or relationships
necessary to accommodate them.
- Decide whether there are any other attributes or
which must be included now
to accommodate future developments.
- Check that your choices of entity classes,
relationships, and attributes
still seem appropriate.
Check that all transactions can be supported at the attribute
If necessary repeat the procedure from the beginning.
- Delete any superfluous entity classes.
Last updated July 5, 2001.
This page maintained by
Prof. Tim Craven
E-mail (text/plain only): email@example.com
Faculty of Information and
University of Western
Canada, N6A 5B7