When an object is mapped into software representation, it consists of 2 parts:

1. PRIVATE data structure
characteristics of private data structure are refered to as ATTRIBUTES

2. PROCESSES that may correctly change the data structure
processes are refered to as OPERATIONS or METHODS

A private data structure called Person would have the following attributes.

1. First name
2. Last name
3. Age
4. Weight

A private data structure for Car would have the following attributes.

1. Colour
2. Weight
3. Model-Year

The Methods of Person object would be:-

1. set_first_name
2. get_first_name
3. set_last_name
4. get_middle_name etc..

Similar methods exists for car or any other object attributes.

The way you analyze a problem (break it down) will give you a particular set of objects. There are three helpful ways to help you identify objects when you are designing a system, which are:

[1] A Checklist of Kinds of Objects (Pressman)

a) External entities
b) Things
c) Occurrences or events
d) Roles
e) Organisational units
f) Places
g) Structures

[2] Grammatical Parse of a Piece of Text Describing the Problem and Outline Solution.

In the grammatical parse you select the nouns and noun phrases as the potential objects and verbs as possible operations performed on or by the objects.

[3] Six Characteristics to Filter a List of Potential Objects. (Coad Yourdon)

    a) Retained Information - the object needs to remember information.
    b) Needed Service - the object has operations which change its attributes.
    c) Common Attributes - all occurences of an object have the attributes.
    d) Common Operations - All occurences of an object have the operations.
    e) Essential Requirements - external entities which produce consume information.
    f) Multiple Attributes - single attributes might be thought of as being an attribute
        of a larger object, not an object in their own right.

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