8 research outputs found
The CIFF Proof Procedure for Abductive Logic Programming with Constraints: Theory, Implementation and Experiments
We present the CIFF proof procedure for abductive logic programming with
constraints, and we prove its correctness. CIFF is an extension of the IFF
proof procedure for abductive logic programming, relaxing the original
restrictions over variable quantification (allowedness conditions) and
incorporating a constraint solver to deal with numerical constraints as in
constraint logic programming. Finally, we describe the CIFF system, comparing
it with state of the art abductive systems and answer set solvers and showing
how to use it to program some applications. (To appear in Theory and Practice
of Logic Programming - TPLP)
LOGIC AND CONSTRAINT PROGRAMMING FOR COMPUTATIONAL SUSTAINABILITY
Computational Sustainability is an interdisciplinary field that aims to develop computational
and mathematical models and methods for decision making concerning
the management and allocation of resources in order to help solve environmental
problems.
This thesis deals with a broad spectrum of such problems (energy efficiency, water
management, limiting greenhouse gas emissions and fuel consumption) giving
a contribution towards their solution by means of Logic Programming (LP) and
Constraint Programming (CP), declarative paradigms from Artificial Intelligence
of proven solidity.
The problems described in this thesis were proposed by experts of the respective
domains and tested on the real data instances they provided. The results are encouraging
and show the aptness of the chosen methodologies and approaches.
The overall aim of this work is twofold: both to address real world problems
in order to achieve practical results and to get, from the application of LP and
CP technologies to complex scenarios, feedback and directions useful for their
improvement
Distributed Abductive Reasoning: Theory, Implementation and Application
Abductive reasoning is a powerful logic inference mechanism that allows assumptions to be
made during answer computation for a query, and thus is suitable for reasoning over incomplete
knowledge. Multi-agent hypothetical reasoning is the application of abduction in a distributed
setting, where each computational agent has its local knowledge representing partial world and
the union of all agents' knowledge is still incomplete. It is different from simple distributed
query processing because the assumptions made by the agents must also be consistent with
global constraints.
Multi-agent hypothetical reasoning has many potential applications, such as collaborative planning
and scheduling, distributed diagnosis and cognitive perception. Many of these applications
require the representation of arithmetic constraints in their problem specifications as well as
constraint satisfaction support during the computation. In addition, some applications may
have confidentiality concerns as restrictions on the information that can be exchanged between
the agents during their collaboration. Although a limited number of distributed abductive systems
have been developed, none of them is generic enough to support the above requirements.
In this thesis we develop, in the spirit of Logic Programming, a generic and extensible distributed
abductive system that has the potential to target a wide range of distributed problem
solving applications. The underlying distributed inference algorithm incorporates constraint
satisfaction and allows non-ground conditional answers to be computed. Its soundness and
completeness have been proved. The algorithm is customisable in that different inference and
coordination strategies (such as goal selection and agent selection strategies) can be adopted
while maintaining correctness. A customisation that supports confidentiality during problem
solving has been developed, and is used in application domains such as distributed security
policy analysis. Finally, for evaluation purposes, a
flexible experimental environment has been
built for automatically generating different classes of distributed abductive constraint logic programs.
This environment has been used to conduct empirical investigation of the performance
of the customised system
The computational behaviour of the SCIFF abductive proof procedure and the SOCS-SI system
The high computational cost of abduction has limited the application
of this powerful and expressive formalism to practical cases.
SCIFF is an abductive proof procedure used for verifying the
compliance of agent behaviour to interaction protocols in multi-agent
systems; SCIFF has been integrated in SOCS-SI, a system able to
observe the agent interaction, pass it to SCIFF for the reasoning
process and to display in a GUI the results of the SCIFF
computation.
In order to assess the applicability of sciff and SOCS-SI to
practical cases, we have evaluated qualitatively and experimentally
(not yet formally) their computational behaviour, concerning
limitations and scalability. In this paper we show the results of
the analysis
An Unexpected Journey: Towards Runtime Verification of Multiagent Systems and Beyond
The Trace Expression formalism derives from works started in 2012 and is
mainly used to specify and verify interaction protocols at runtime, but other
applications have been devised. More specically, this thesis describes how
to extend and apply such formalism in the engineering process of distributed
articial intelligence systems (such as Multiagent systems).
This thesis extends the state of the art through four dierent contributions:
1. Theoretical: the thesis extends the original formalism in order to represent
also parametric and probabilistic specications (parametric trace
expressions and probabilistic trace expressions respectively).
2. Algorithmic: the thesis proposes algorithms for verifying trace expressions
at runtime in a decentralized way. The algorithms have been
designed to be as general as possible, but their implementation and
experimentation address scenarios where the modelled and observed
events are communicative events (interactions) inside a multiagent system.
3. Application: the thesis analyzes the relations between runtime and static
verication (e.g. model checking) proposing hybrid integrations in both
directions. First of all, the thesis proposes a trace expression model
checking approach where it shows how to statically verify LTL property
on a trace expression specication. After that, the thesis presents a
novel approach for supporting static verication through the addition
of monitors at runtime (post-process).
4. Implementation: the thesis presents RIVERtools, a tool supporting the
writing, the syntactic analysis and the decentralization of trace expressions