Data Modeling with the Entity-Relationship Model - Database Processing: Fundamentals, Design, and Implementation - page 221

5.58 Examine the list of stock quotes in Figure 5-55. Using the structure and example data
items in this list, do the following:

Create a single-entity data model for this list. Specify the identifier and attributes. a.

Modify your answer to A to include the entities COMPANY and INDEX. Specify the
identifier and attributes of the entities and the type and cardinalities of the rela-
tionships. Explain which cardinalities can be inferred from Figure 5-55 and which
need to be checked out with users.

B.

The list in Figure 5-55 is for a quote on a particular day at a particular time of day.
Suppose that the list were changed to show closing daily prices for each of these
stocks and that it includes a new column: QuoteDate. Modify your model in B to
reflect this change.

C.

Change your model in C to include the tracking of a portfolio. Assume the portfolio
has an owner name, a phone number, an e-mail address, and a list of stocks held.
The list includes the identity of the stock and the number of shares held. Specify all
additional entities, their identifiers and attributes, and the type and cardinality of
all relationships.

D.

Change your answer to part D to keep track of portfolio stock purchases and sales
in a portfolio. Specify entities, their identifiers and attributes, and the type and car-
dinality of all relationships.

E.

5.59 Figure 5-56 shows the specifications for single-stage air compressor products. Note
that there are two product categories that are based on Air Performance: The A models
are at 125 pounds per square inch of pressure, and the E models are at 150 pounds per
square inch of pressure. Using the structure and example data items in this list, do the
following:

Create a set of exclusive subtypes to represent these compressors. The supertype
will have attributes for all single-stage compressors, and the subtypes will have
attributes for products having the two different types of Air Performance. Assume
that there might be additional products with different types of Air Performance.
Specify the entities, identifiers, attributes, relationships, type of category cluster,
and possible determinant.

a.

Figure 5-55
Stock Quotations