Context Representation

Contexts are abstract objects. Some contexts will be rich objects, like situations in situation calculus. For example, the context associated with a conversation is rich; we cannot list all the common assumptions of the participants. Thus we don't purport to describe such contexts completely; we only say something about them. On the other hand, the contexts associated with certain micro theories are poor and can be completely described.

Here are some examples:

• This Example

  

  asserts that it is true in the context of the Sherlock Holmes stories that Holmes is a detective. Here c0 is considered to be an outer context.

• In the context
  , Holmes's mother's maiden name does not have a value. We also have

  

  In this context, Holmes's mother's maiden name has a value, namely Jackson, and it would still have that value even if no-one today knew it.

• ist(c1,at(akapoor, PITT)) is the assertion that Anupama Kapoor is at Pittsburgh University in a context in which it is given that akapoor stands for the login Id of the student and that PITT stands for Pittsburgh University. The context c1 may be one in which the symbol at is taken in the sense of being regularly at a place, rather than meaning momentarily at the place. In another context c2, at(akapoor,PITT) may mean physical presence at Pitt at a certain instant.