**1.**
Guha has put contexts into Cyc, largely in the form of microtheories.
The example is a microtheory. See [29] for
some of the details.

**2.**
We have mentioned various ways of getting new contexts
from old ones: by specializing the time or place, by specializing the
situation, by making abbreviations, by specializing the subject matter
(e.g. to U.S. legal history), by making assumptions and by
specializing to the context of a conversation. These are all
specializations of one kind or another. Getting a new context
by transcending an old context, e.g. by dropping the assumption of a
gravitational field, gives rise to a whole new class of ways
of getting new contexts.

These are too many ways of getting new contexts to be treated separately.

**3.**
We have used natural language examples in this article,
although natural language is not our main concern. Nevertheless,
we hope that formalizing context in the ways we propose may be
useful in studying the semantics of natural language. Natural
language exhibits the striking phenomenon that context may
vary on a very small scale; several contexts may occur in a
single sentence.

Consider the context of an operation in which the surgeon says, ``Scalpel''. In context, this may be equivalent to the sentence, ``Please give me the number 3 scalpel''.

**4.**
can be considered a modal operator dependent on *c* applied
to *p*. In this sense much of our analysis amounts to reasoning in a certain
systems of modal logic or temporal logic; see
[16, 22, 8].

In the propositional case, given a context language containing a set
of contexts *C*, we can define a modal language containing
modalities , one for each context from
*C*.
By replacing each occurrence of
with
, we
can define
a bijective translation function which to each formula of the
propositional context logic assigns a well-formed
modal formula.
Based on this translation,
[12] shows a reduction of the
propositional logic of context to a propositional multi-modal logic. Similar
results are obtained using proof theoretic tools in [26].

However, these results do not carry over to the quantificational case.
The quantificational logic of context, for example, enables us to
state that the formula is true in contexts which satisfy
some property *p*(*x*) as follows:
This formula has no obvious translation into standard multi-modal logic, and
the meaning of such formulas which quantify over modalities is
beyond the analysis commonly done in quantificational modal logic.
See [9] for details.

**5.**
Proof theoretic approach to context has been emphasized by Richard
W. Weyhrauch and Fausto Giunchiglia and his group. See
[60, 61, 25, 26, 17].

**6.**
It would be useful to have a formal theory of the natural phenomenon of
context, e.g.in human life, as distinct from inventing a form of context useful
for AI systems using logic for representation. This is likely to be an *
approximate theory* in the sense described in [37]. That is, the term
``context'' will appear in useful axioms and other sentences but will not have a
definition involving ``if and only if''. [30] outlines one such
taxonomy of contexts.

**7.**
Useful nonmonotonic rules for lifting will surely be more complex
than the examples given. See [20] for context
limited consistency check.

**8.**
Theories along the lines of [6] are in many ways similar
to formal theories of context; [59] gives one comparison.
[44, 2] represent context using the tools of
situation theory.

**9.**
[23] proposes fibred semantics as a way of ``weaving of
logics''. For a comparison of this approach to the formal theories of context,
see [24].

Sun Jul 12 14:45:30 PDT 1998