3. Observations and Measurements
Many computer systems record information about objects in the real world. This information finds its way into computer systems as records, attributes, objects, and various other representations. The typical route is to record a piece of information as an attribute to an object. For example, the fact that I weigh 185 pounds would be recorded in an attribute of a person type. This chapter examines how this approach fails and suggests more sophisticated approaches.
We begin by discussing quantity (3.1)—a type that combines a number with the unit that is associated with it. By combining numbers and units, we are able to model the world more exactly. With quantities and their units modeled as objects, we can also describe ...
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