15316733
Admissible and Restrained Revision
As partial justification of their framework for iterated belief revision Darwiche and Pearl convincingly argued against Boutilier's natural revision and provided a prototypical revision operator that fits into their scheme. We show that the Darwiche-Pearl arguments lead naturally to the acceptance of a smaller class of operators which we refer to as admissible. Admissible revision ensures that the penultimate input is not ignored completely, thereby eliminating natural revision, but includes the Darwiche-Pearl operator, Nayak's lexicographic revision operator, and a newly introduced operator called restrained revision. We demonstrate that restrained revision is the most conservative of admissible revision operators, effecting as few changes as possible, while lexicographic revision is the least conservative, and point out that restrained revision can also be viewed as a composite operator, consisting of natural revision preceded by an application of a "backwards revision" operator previously studied by Papini. Finally, we propose the establishment of a principled approach for choosing an appropriate revision operator in different contexts and discuss future work.
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].
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.
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.
116472242
Proceedings of the second Australasian workshop on Advances in ontologies - Volume 72
The first two Australasian Ontology Workshops (AOW 2005 and AOW 2006) were held in Sydney and Hobart, respectively, both as workshops of the Australian Joint Conference on Artificial Intelligence (AI'05, and AI'06). This tradition is being continued this year, with AOW 2007 being held on the Gold Coast in Queensland, Australia, again as workshop of the Australian Joint Conference on Artificial Intelligence (AI'07).
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.
1383149
An Artificial Chemistry for Networking
Chemical computing models have been proposed since the 1980ies for expressing concurrent computations in elegant ways for shared memory systems. In this paper we look at the distributed case of network protocol execution for which we developed an online artificial chemistry. In this chemistry, data packets become molecules which can interact with each other, yielding computation networks comparable to biological metabolisms. Using this execution support, we show how to compute an average over arbitrary networking topologies and relate it to traditional forms of implementing load balancing. Our long-term interest lies in the robust implementation, operation and evolution of network protocols, for which artificial chemistries provide a promising basis.
3125532
Structure-based design of potent CDK1 inhibitors derived from olomoucine
Cyclin-dependent kinase 1 (CDK1), an enzyme participating in the regulation of the cell cycle, constitutes a possible target in the search for new antitumor agents. Starting from the purine derivative olomoucine and following a structure-based approach, potent inhibitors of this enzyme were rapidly identified. The molecular modeling aspects of this work are described.
11977605
Collage Grammars for Collision-Free Growing of Objects in 3D Scenes
In the real world, solid objects rarely collide without serious damage. We study collision-freeness in the context of collage grammars, which are picture- and scene-generating devices based on hyperedge replacement. We identify a type of collage grammars that generate only collision-free collages, and prove the undecidability of the problem whether an arbitrary collage grammar generates any collision-free collage. Moreover, we discuss collision avoidance in the derivation process as an appropriate tool for practical modelling purposes.
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.
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.