2,883 research outputs found
A Topological-Based Method for Allocating Sensors by Using CSP Techniques
Model-based diagnosis enables isolation of faults of a system.
The diagnosis process uses a set of sensors (observations) and a model
of the system in order to explain a wrong behaviour. In this work, a
new approach is proposed with the aim of improving the computational
complexity for isolating faults in a system. The key idea is the addition of
a set of new sensors which allows the improvement of the diagnosability
of the system. The methodology is based on constraint programming
and a greedy method for improving the computational complexity of the
CSP resolution. Our approach maintains the requirements of the user
(detectability, diagnosability,. . .).Ministerio de Ciencia y Tecnología DPI2003-07146-C02-0
An Integration of FDI and DX Techniques for Determining the Minimal Diagnosis in an Automatic Way
Two communities work in parallel in model-based diagnosis:
FDI and DX. In this work an integration of the FDI and the DX communities
is proposed. Only relevant information for the identification of the
minimal diagnosis is used. In the first step, the system is divided into
clusters of components, and each cluster is separated into nodes. The
minimal and necessary set of contexts is then obtained for each cluster.
These two steps automatically reduce the computational complexity
since only the essential contexts are generated. In the last step, a signature
matrix and a set of rules are used in order to obtain the minimal
diagnosis. The evaluation of the signature matrix is on-line, the rest of
the process is totally off-line.Ministerio de Ciencia y Tecnología DPI2003-07146-C02-0
Diagnosing Errors in DbC Programs Using Constraint Programming
Model-Based Diagnosis allows to determine why a correctly
designed system does not work as it was expected. In this paper, we propose
a methodology for software diagnosis which is based on the combination
of Design by Contract, Model-Based Diagnosis and Constraint
Programming. The contracts are specified by assertions embedded in the
source code. These assertions and an abstraction of the source code are
transformed into constraints, in order to obtain the model of the system.
Afterwards, a goal function is created for detecting which assertions or
source code statements are incorrect. The application of this methodology
is automatic and is based on Constraint Programming techniques.
The originality of this work stems from the transformation of contracts
and source code into constraints, in order to determine which assertions
and source code statements are not consistent with the specification.Ministerio de Ciencia y Tecnología DPI2003-07146-C02-0
Applying Constraint Databases in the Determination of Potential Minimal Conflicts to Polynomial Model-Based Diagnosis
Model-based Diagnosis allows the identification of the parts
which fail in a system. The models are based on the knowledge of the
system to diagnose, and may be represented by constraints associated
to the components. The variables of these constraints can be observable
or non-observable, depending on the situation of the sensors. In order to
obtain the potential minimal diagnosis in a system, an important issue is
related to finding out the potential minimal conflicts in an efficient way.
We consider that Constraint Databases represent an excellent option in
order to solve this problem in complex systems.
In this work we have used a novel logical architecture of Constraint
Databases which has allowed obtaining these potential conflicts by means
of the corresponding queries. Moreover, we have considered Gröbner
Bases as a projection operator to obtain the potential minimal conflicts
of a system. The first results obtained on this work, which are shown in
a heat exchangers example, have been very promising.Ministerio de Ciencia y Tecnología DPI2003-07146-C02-0
Developing a labelled object-relational constraint database architecture for the projection operator
Current relational databases have been developed in order to improve the handling of
stored data, however, there are some types of information that have to be analysed for
which no suitable tools are available. These new types of data can be represented and treated
as constraints, allowing a set of data to be represented through equations, inequations
and Boolean combinations of both. To this end, constraint databases were defined and
some prototypes were developed. Since there are aspects that can be improved, we propose
a new architecture called labelled object-relational constraint database (LORCDB). This provides
more expressiveness, since the database is adapted in order to support more types of
data, instead of the data having to be adapted to the database. In this paper, the projection
operator of SQL is extended so that it works with linear and polynomial constraints and
variables of constraints. In order to optimize query evaluation efficiency, some strategies
and algorithms have been used to obtain an efficient query plan.
Most work on constraint databases uses spatiotemporal data as case studies. However,
this paper proposes model-based diagnosis since it is a highly potential research area,
and model-based diagnosis permits more complicated queries than spatiotemporal examples.
Our architecture permits the queries over constraints to be defined over different sets
of variables by using symbolic substitution and elimination of variables.Ministerio de Ciencia y Tecnología DPI2006-15476-C02-0
NMUS: Structural Analysis for Improving the Derivation of All MUSes in Overconstrained Numeric CSPs
Models are used in science and engineering for experimentation,
analysis, model-based diagnosis, design and planning/sheduling
applications. Many of these models are overconstrained Numeric Constraint
Satisfaction Problems (NCSP), where the numeric constraints
could have linear or polynomial relations. In practical scenarios, it is
very useful to know which parts of the overconstrained NCSP instances
cause the unsolvability.
Although there are algorithms to find all optimal solutions for this
problem, they are computationally expensive, and hence may not be applicable
to large and real-world problems. Our objective is to improve
the performance of these algorithms for numeric domains using structural
analysis. We provide experimental results showing that the use of
the different strategies proposed leads to a substantially improved performance
and it facilitates the application of solving larger and more
realistic problems.Ministerio de Educación y Ciencia DIP2006-15476-C02-0
A heuristic polynomial algorithm for local inconsistency diagnosis in firewall rule sets
Firewall ACLs can contain inconsistencies. There is an inconsistency if different actions can be taken on the
same flow of traffic, depending on the ordering of the rules. Inconsistent rules should be notified to the
system administrator in order to remove them. Minimal diagnosis and characterization of inconsistencies is
a combinatorial problem. Although many algorithms have been proposed to solve this problem, all reviewed
ones work with the full ACL with no approximate heuristics, giving minimal and complete results, but
making the problem intractable for large, real-life ACLs. In this paper we take a different approach. First,
we deeply analyze the inconsistency diagnosis in firewall ACLs problem, and propose to split the process in
several parts that can be solved sequentially: inconsistency detection, inconsistent rules identification, and
inconsistency characterization. We present polynomial heuristic algorithms for the first two parts of the
problem: detection and identification (diagnosis) of inconsistent rules. The algorithms return several
independent clusters of inconsistent rules that can be characterized against a fault taxonomy. These clusters
contains all inconsistent rules of the ACL (algorithms are complete), but the algorithms not necessarily give
the minimum number of clusters. The main advantage of the proposed heuristic diagnosis process is that
optimal characterization can be now applied to several smaller problems (the result of the diagnosis process)
rather than to the whole ACL, resulting in an effective computational complexity reduction at the cost of not
having the minimal diagnosis. Experimental results with real ACLs are given.Ministerio de Educación y Ciencia DPI2006-15476-C02-0
Fast algorithms for consistency-based diagnosis of firewall rule sets
Firewalls provide the first line of defence of nearly
all networked institutions today. However, Firewall
ACL management suffer some problems that need to be
addressed in order to be effective. The most studied
one is rule set consistency. There is an inconsistency if
different actions can be taken on the same traffic,
depending on the ordering of the rules. In this paper a
new algorithm to diagnose inconsistencies in firewall
rule sets is presented. Although many algorithms have
been proposed to address this problem, the presented
one is a big improvement over them, due to its low
algorithmic and memory complexity, even in worst
case. In addition, there is no need to pre-process in
any way the rule set previous to the application of the
algorithms. We also present experimental results with
real rule sets that validate our proposal.Ministerio de Educación y Ciencia DPI2006-15476-C02-0
Behavioral pattern analysis of secure migration and communications in eCommerce using cryptographic protocols on a mobile MAS platform
Mobile Multi-Agent Systems (MAS) systems can be
used with real success in a growing number of
eCommerce applications nowadays. Security has been
identified as numerous times by different researchers
as a top criterion for the acceptance of mobile agent
adoption. In this paper we present an in-depth analysis
of behavior patterns of a mobile MAS platform when
using different cryptographic protocols to assure
communication and migration integrity and
confidentiality. Different use case sceneries of
eCommerce applications as well as many other aspects
have been studied, such as overhead, different
communication patterns, different loads and
bandwidth issues. This work is also extensible to other
mobile and non-mobile MAS platforms. The results
obtained can be used and should be taken into account
by designers and implementers of secure mobile and
also non-mobile agent platforms and agents.European Union TeleCARE IST-2000-2760
Constraint satisfaction techniques for diagnosing errors in Design by Contract software
Design by Contract enables the development of more reliable
and robust software applications. In this paper, a methodology
that diagnoses errors in software is proposed. This
is based on the combination of Design by Contract, Modelbased
Diagnosis and Constraint Programming. Contracts
are specified by using assertions. These assertions together
with an abstraction of the source code are transformed into
constraints. The methodology detects if the contracts are
consistent, and if there are incompatibilities between contracts
and source code. The process is automatic and is
based on constraint programming.Ministerio de Ciencia y Tecnología DPI2003-07146-C02-0
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