Finding Classes

Copyright © 1999 Patrick McDermott

College of Alamedapmcdermott@peralta.edu

A Quest:David, Earl of Huntingdon, 1120from A Critical Inquiry into Antient Armour (1842)

A Class Tracks…

An Entity: A Thing the Business needs to know about.

At this stage, a business person should be able to understand every one of them.

“Entity” is best defined by examples…

People

George Romney (1734-1802)Emma, Lady Hamilton (1761-1815)1786

Albrecht Dürer (1471-1528)Self-Portrait1498

Places

Things

Gustave Caillebotte (1848–94)Le pont de l’Europe

1877

Katsushika Hokusai 葛飾北斎 (1760-1849)Fuji from beneath Mannen Bridge in Fukagawa

Fukagawa mannenbashi shita深川万年橋下

36 Views of Mount Fuji富嶽三十六景 Fugaku Sanjūrokkei

ca. 1831-1834

Events

Meeting of the RailsPromontory Point, Utah, 1869

Andrew J. Russell

OrganizationsDorothea Lange (1895-1965)Richmond shipyards, 1943

Dorothea Lange (1895-1965)End of shift 3:30, Richmond, California

September 1943

Examples of Classes

Tangible• People

– Employees– Students

• Places– Shipping Locations– Offices

• Things– Equipment– Vehicles

Intangible• Accounts• Cost Centers• Departments• Grades

You need a Class if…• There’s a form• There’s a number• There’s a file• There are several copies• It’s Important• NOTE—

– Sections and boxes on Forms– The name might not be obvious

They’re Everywhere!

Classes have Responsibilities• Personification Helps

– What if a person, not a computer, does it?– Obligation or Contract

• Know Things– Invoice: Know who the Customer is

• Do Things– Invoice: Compute Total