15047002
Knowledge Integration for Description Logics
Description logic reasoners are able to detect incoherences (such as logical inconsistency and concept unsatisfiability) in knowledge bases, but provide little support for resolving them. We propose to recast techniques for propositional inconsistency management into the description logic setting. We show that the additional structure afforded by description logic statements can be used to refine these techniques. Our focus in this paper is on the formal semantics for such techniques, although we do provide high-level decision procedures for the knowledge integration strategies discussed.
1613464
Merging Epistemic States
Intelligent agents are often faced with the problem of trying to merge possibly conflicting pieces of information obtained from different sources into a consistent view of the world. We propose a framework for the modelling of such merging operations with roots in the work of Spohn [14]. Unlike most approaches we focus on the merging of epistemic states, not knowledge bases. We construct a number of plausible merging operations and measure them against various properties that merging operations ought to satisfy. Finally, we discuss the connection between merging and the use of infobases [9], [10].
61294495
Proceedings of the 2005 Australasian Ontology Workshop - Volume 58
16520645
Equilibria in social belief removal
In studies of multi-agent interaction, especially in game theory, the notion of equilibrium often plays a prominent role. A typical scenario for the belief merging problem is one in which several agents pool their beliefs together to form a consistent “group” picture of the world. The aim of this paper is to define and study new notions of equilibria in belief merging. To do so, we assume the agents arrive at consistency via the use of a social belief removal function, in which each agent, using his own individual removal function, removes some belief from his stock of beliefs. We examine several notions of equilibria in this setting, assuming a general framework for individual belief removal due to Booth et al. We look at their inter-relations as well as prove their existence or otherwise. We also show how our equilibria can be seen as a generalisation of the idea of taking maximal consistent subsets of agents.
38685809
A General Family of Preferential Belief Removal Operators
Most belief change operators in the AGM tradition assume an underlying plausibility ordering over the possible worlds which is transitive and complete. A unifying structure for these operators, based on supplementing the plausibility ordering with a second, guiding, relation over the worlds was presented in [5]. However it is not always reasonable to assume completeness of the underlying ordering. In this paper we generalise the structure of [5] to allow incomparabilities between worlds. We axiomatise the resulting class of belief removal functions, and show that it includes an important family of removal functions based on finite prioritised belief bases.
10175705
Next Steps in Propositional Horn Contraction
Standard belief contraction assumes an underlying logic containing full classical propositional logic, but there are good reasons for considering contraction in less expressive logics. In this paper we focus on Horn logic. In addition to being of interest in its own right, our choice is motivated by the use of Horn logic in several areas, including ontology reasoning in description logics. We consider three versions of contraction: entailment-based and inconsistency-based contraction (e-contraction and i-contraction, resp.), introduced by Delgrande for Horn logic, and package contraction (p-contraction), studied by Fuhrmann and Hansson for the classical case. We show that the standard basic form of contraction, partial meet, is too strong in the Horn case. We define more appropriate notions of basic contraction for all three types above, and provide associated representation results in terms of postulates. Our results stand in contrast to Delgrande's conjectures that orderly maxichoice is the appropriate contraction for both e- and i-contraction. Our interest in p-contraction stems from its relationship with an important reasoning task in ontological reasoning: repairing the subsumption hierarchy in EL. This is closely related to p-contraction with sets of basic Horn clauses (Horn clauses of the form p → q). We show that this restricted version of p-contraction can also be represented as i-contraction.
16322351
On algorithmically checking whether a Hilbert series comes from a complete intersection
It is not possible to determine from the Hilbert series whether a commutative Z-graded Noetherian algebra is a complete intersection. Nevertheless, the Hilbert series of a complete intersection satisfies very stringent conditions and we define a concept CI-type for formal power series, that embodies some of these necessary properties. This definition becomes interesting mainly for algebras that are not standard i.e. not generated in degree 1. For the class of formal power series that occur as the Hilbert series of Z-graded Noetherian Cohen-Macaulay algebras, the main result is a criterion for a series to be of CI-type, that is formulated in terms of properties of truncated power series. Hence it can be used as the basis for an algorithm that provides in a finite number of steps either a rational function expression of the formal power series, or the information that the truncated power series is not of CI-type. Also sample computations using this algorithm on some non-standard graded invariant algebras are described.
18488287
A Self-Healing Multipath Routing Protocol
This paper introduces a self-healing multipath routing solution that is resilient to code knock-out attacks i.e., the software copes with changing network topologies and perturbations of link characteristics as well as loss of parts of its code base. We use the Fraglets artificial chemistry for building a distributed reaction network that spans the whole network topology. Unlike the use of explicit metric values in today's network protocols, our approach relies on the concentration of routing table entries to stochastically decide which path a packet should take through the network. A reinforcement mechanism rewards successful forwarding rules that compete against each other for delivering data packets over alternative paths. Our self-healing solution is based on the systematic use of self-replicating code that constantly rewrites itself.
25161687
TAS and IsaWin: Generic Interfaces for Transformational Program Development and Theorem Proving
We present a new approach to the implementation of graphical user interfaces (GUIs) for formal program development systems like transformation systems or interactive theorem provers. Its distinguishing feature is a generic, open system design which allows the development of a family of tools for different formal methods on a sound logical basis with a uniform appearance. The context of this work is the UniForM project [KPO+95], the aim of which is to develop a framework integrating different formal methods in a logically consistent way. Consistency is achieved by encoding formal methods such as CSP and Z in the theorem prover Isabelle [Pau94], which is used to perform the program development as well as to prove the correctness of the transformation rules. One of the main UniForM objectives is to enable non-expert users to actually perform at least part of the developmen~ themselves. Hence there is a crucial need for an encapsulation technique of these Isabelle encodings providing a generic way of building graphical user interfaces.
2586073
Robustness to Code and Data Deletion in Autocatalytic Quines
Software systems nowadays are becoming increasingly complex and vulnerable to all sorts of failures and attacks. There is a rising need for robust self-repairing systems able to restore full functionality in the face of internal and external perturbations, including those that affect their own code base. However, it is difficult to achieve code self-repair with conventional programming models. 
 
We propose and demonstrate a solution to this problem based on self-replicating programs in an artificial chemistry. In this model, execution proceeds by chemical reactions that modify virtual molecules carrying code and data. Self-repair is achieved by what we call autocatalytic quines : programs that permanently reproduce their own code base. The concentration of instructions reflects the health of the system, and is kept stable by the instructions themselves. We show how the chemistry of such programs enables them to withstand arbitrary amounts of random code and data deletion, without affecting the results of their computations.
29605470
A Real-Time Low-Power Stereo Vision Engine Using Semi-Global Matching
Many real-time stereo vision systems are available on low-power platforms. They all either use a local correlation-like stereo engine or perform dynamic programming variants on a scan-line. However, when looking at high-performance global stereo methods as listed in the upper third of the Middlebury database, the low-power real-time implementations for these methods are still missing. We propose a real-time implementation of the semi-global matching algorithm with algorithmic extensions for automotive applications on a reconfigurable hardware platform resulting in a low power consumption of under 3W. The algorithm runs at 25Hz processing image pairs of size 750x480 pixels and computing stereo on a 680x400 image part with up to a maximum of 128 disparities.