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UML (Unified Modeling Language)

Increasingly, companies are standardizing the way in which they model data by selecting

a particular approach to data modeling and using it throughout their database development

projects. A popular high-level data model used in conceptual/logical database design,

and the one we use in this book, is based on the concepts of the Entity–Relationship

(ER) model. Currently there is no standard notation for an ER model. Most books

that cover database design for relational DBMSs tend to use one of two conventional

notations:

n Chen’s notation, consisting of rectangles representing entities and diamonds representing

relationships, with lines linking the rectangles and diamonds; or

n Crow’s Feet notation, again consisting of rectangles representing entities and lines

between entities representing relationships, with a crow’s foot at one end of a line

representing a one-to-many relationship.

Both notations are well supported by current CASE tools. However, they can be quite

cumbersome to use and a bit difficult to explain. Prior to this edition, we used Chen’s

notation. However, following an extensive questionnaire carried out by Pearson Education,

there was a general consensus that the notation should be changed to the latest objectoriented

modeling language called UML (Unified Modeling Language). UML is a

notation that combines elements from the three major strands of object-oriented design:

Rumbaugh’s OMT modeling, Booch’s Object-Oriented Analysis and Design, and

Jacobson’s Objectory.

There are three primary reasons for adopting a different notation: (1) UML is becoming

an industry standard; for example, the Object Management Group (OMG) has

adopted the UML as the standard notation for object methods; (2) UML is arguably

clearer and easier to use; (3) UML is now being adopted within academia for teaching

object-oriented analysis and design, and using UML in database modules provides

more synergy. Therefore, in this edition we have adopted the class diagram notation

from UML. We believe you will find this notation easier to understand and use. Prior to

making this move to UML, we spent a considerable amount of time experimenting

with UML and checking its suitability for database design. We concluded this work by

publishing a book through Pearson Education called Database Solutions: A Step-by-Step

Guide to Building Databases. This book uses the methodology to design and build

databases for two case studies, one with the target DBMS as Microsoft Office Access and

one with the target database as Oracle. This book also contains many other case studies

with sample solutions.

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