The design of object oriented system is largely the identification of the objects in the system and designing the language of those objects. ==== Object protocols

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The language of an object is called the object protocol. It is the set of messages it responds to and their definitions. Common language is essential for collaboration.

==== Attributes and Parameters

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The most common and simplest object protocol of objects is attribute access and assignment. Simple objects are simply a collection of attribute value pairs which may be accessed or assigned using the name of the attribute. Similar instances can be created using the attribute set overriding some or all of the values. Values are also objects.

==== Methods

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Methods are values that are executed to obtain a value to return. These may use other attributes and messages to other referenced objects to evaluate the final results. As with attributes, similar instances can be created using the attribute set overriding some or all of the methods. Methods are also objects.

==== Universal operations

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At the system level this involves a common language for basic operations that are applicable. Protocols at this level include messages such as get, put, link, unlink, do. The idea is that our objects support the complete protocols of FirstClassObjectsOnTheWeb.

==== Models, frameworks and design patterns

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In the middle layer common language is achieved by using general abstractions such as Numbers, Strings, Lists, Stacks and Sets, and reusable design patterns for system architecture such as Model, View, Controller (MVC) and application Layers using standard object protocols whenever appropriate.

==== Application level interfaces and protocols

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At the user level, it is desirable to invent an object language that closely corresponds to the application using standard object protocols whenever appropriate.