90 research outputs found
Relating Knowledge and Coordinated Action: The Knowledge of Preconditions Principle
The Knowledge of Preconditions principle (KoP) is proposed as a widely
applicable connection between knowledge and action in multi-agent systems.
Roughly speaking, it asserts that if some condition is a necessary condition
for performing a given action A, then knowing that this condition holds is also
a necessary condition for performing A. Since the specifications of tasks often
involve necessary conditions for actions, the KoP principle shows that such
specifications induce knowledge preconditions for the actions. Distributed
protocols or multi-agent plans that satisfy the specifications must ensure that
this knowledge be attained, and that it is detected by the agents as a
condition for action. The knowledge of preconditions principle is formalised in
the runs and systems framework, and is proven to hold in a wide class of
settings. Well-known connections between knowledge and coordinated action are
extended and shown to derive directly from the KoP principle: a "common
knowledge of preconditions" principle is established showing that common
knowledge is a necessary condition for performing simultaneous actions, and a
"nested knowledge of preconditions" principle is proven, showing that
coordinating actions to be performed in linear temporal order requires a
corresponding form of nested knowledge.Comment: In Proceedings TARK 2015, arXiv:1606.0729
Automated proof search system for logic of correlated knowledge
The automated proof search system and decidability for logic of correlated
knowledge is presented in this paper. The core of the proof system is the
sequent calculus with the properties of soundness, completeness, admissibility
of cut and structural rules, and invertibility of all rules. The proof search
procedure based on the sequent calculus performs automated terminating proof
search and allows us to achieve decision result for logic of correlated
knowledge
A note on knowledge-based programs and specifications
Knowledge-based program are programs with explicit tests for knowledge. They
have been used successfully in a number of applications. Sanders has pointed
out what seem to be a counterintuitive property of knowledge-based programs.
Roughly speaking, they do not satisfy a certain monotonicity property, while
standard programs (ones without tests for knowledge) do. It is shown that there
are two ways of defining the monotonicity property, which agree for standard
programs. Knowledge-based programs satisfy the first, but do not satisfy the
second. It is further argued by example that the fact that they do not satisfy
the second is actually a feature, not a problem. Moreover, once we allow the
more general class of knowledge-based specifications, standard programs do not
satisfy the monotonicity property either.Comment: To appear, Distributed Computin
Common Knowledge in Email Exchanges
We consider a framework in which a group of agents communicates by means of
emails, with the possibility of replies, forwards and blind carbon copies
(BCC). We study the epistemic consequences of such email exchanges by
introducing an appropriate epistemic language and semantics. This allows us to
find out what agents learn from the emails they receive and to determine when a
group of agents acquires common knowledge of the fact that an email was sent.
We also show that in our framework from the epistemic point of view the BCC
feature of emails cannot be simulated using messages without BCC recipients.Comment: 34 pages. To appear in ACM Transactions on Computational Logi
Reasoning About Knowledge of Unawareness
Awareness has been shown to be a useful addition to standard epistemic logic
for many applications. However, standard propositional logics for knowledge and
awareness cannot express the fact that an agent knows that there are facts of
which he is unaware without there being an explicit fact that the agent knows
he is unaware of. We propose a logic for reasoning about knowledge of
unawareness, by extending Fagin and Halpern's \emph{Logic of General
Awareness}. The logic allows quantification over variables, so that there is a
formula in the language that can express the fact that ``an agent explicitly
knows that there exists a fact of which he is unaware''. Moreover, that formula
can be true without the agent explicitly knowing that he is unaware of any
particular formula. We provide a sound and complete axiomatization of the
logic, using standard axioms from the literature to capture the quantification
operator. Finally, we show that the validity problem for the logic is
recursively enumerable, but not decidable.Comment: 32 page
Multi-Agent Only Knowing
Levesque introduced a notion of ``only knowing'', with the goal of capturing
certain types of nonmonotonic reasoning. Levesque's logic dealt with only the
case of a single agent. Recently, both Halpern and Lakemeyer independently
attempted to extend Levesque's logic to the multi-agent case. Although there
are a number of similarities in their approaches, there are some significant
differences. In this paper, we reexamine the notion of only knowing, going back
to first principles. In the process, we simplify Levesque's completeness proof,
and point out some problems with the earlier definitions. This leads us to
reconsider what the properties of only knowing ought to be. We provide an axiom
system that captures our desiderata, and show that it has a semantics that
corresponds to it. The axiom system has an added feature of interest: it
includes a modal operator for satisfiability, and thus provides a complete
axiomatization for satisfiability in the logic K45.Comment: To appear, Journal of Logic and Computatio
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