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 . 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.

title: Merging Epistemic States
abstract: 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 . 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 , .

title: Sydney OWL Syntax - towards a Controlled Natural Language Syntax for OWL 1.1
abstract: This paper describes a proposed new syntax that can be used to write and read OWL ontologies in Controlled Natural Language (CNL): a well-defined subset of the English language. Following the lead of Manchester OWL Syntax in making OWL more accessible for non-logicians, and building on the previous success of Schwitter’s PENG (Processable English), the proposed Sydney OWL Syntax enables two-way translation and generation of grammatically correct full English sentences to and from OWL 1.1 functional syntax. Used in conjunction with OWL tools, it is designed to facilitate ontology construction and editing by enabling authors to write an OWL ontology in a defined subset of English. It also improves readability and understanding of OWL statements or whole ontologies, by enabling them to be read as English sentences. It is hoped that by providing the option of an intuitive, easy to use English syntax which requires no specialized knowledge, the broader community will be far more likely to develop and benefit from Semantic Web applications. This paper is a discussion paper covering the scope, design, and examples of Sydney OWL Syntax in use, and the authors invite feedback on all aspects of the proposal via email to krr.sydneysyntax@cse.unsw.edu.au. Working drafts of the full specification are available at http://www.ics.mq.edu.au/~rolfs/sos.

title: Next Steps in Propositional Horn Contraction
abstract: 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.

title: Implementing Iterated Belief Change Via Prime Implicates
abstract: Belief change is concerned with modelling the way in which an idealised (rational) reasoner maintains their beliefs and the way in which those beliefs are modified as the reasoner acquires new information. The AGM [1,3,5] framework is the most widely cited belief change methodology in the literature. It models the reasoner’s belief state as a set of sentences that is logically closed under deduction and provides for three belief change operations: expansion, contraction and revision. Each of the AGM belief change operations is motivated by principles of rationality that are formalised by way of rationality postulates.

title: Modelling Object Typicality in Description Logics
abstract: We present a semantic model of typicality of concept members in description logics (DLs) that accords well with a binary, globalist cognitive model of class membership and typicality. We define a general preferential semantic framework for reasoning with object typicality in DLs. We propose the use of feature vectors to rank concept members according to their defining and characteristic features, which provides a modelling mechanism to specify typicality in composite concepts.

title: Multimedia synchronization techniques: experiences based on different system structures
abstract: Multimedia synchronization" is needed to ensure a temporal ordering of events in multimedi a systems . There are two parts to this problem : the definition of temporal relationships among audio , video, and other data ; and the delivery of the data in accordance with these relationships . It i s important to distinguish between liveand synthetic-synchronization . Live-synch, deals with th e presentation of information in the same order as it was originally collected . For synthetic-synch . various pieces of information must be properly ordered and synchronized in time . Based on th e experiences in DiME and HeiTS, we document the implications of using a hybrid or a unified syste m structures on the required techniques for implementing synchronization .

title: A Self-Healing Multipath Routing Protocol
abstract: 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.

title: Tactic-Based Optimized Compilation of Functional Programs
abstract: Within a framework of correct code-generation from HOL-specifications, we present a particular instance concerned with the optimized compilation of a lazy language (called MiniHaskell) to a strict language (called MiniML). 
 
Both languages are defined as shallow embeddings into denotational semantics based on Scott's cpo's, leading to a derivation of the corresponding operational semantics in order to cross-check the basic definitions. 
 
On this basis, translation rules from one language to the other were formally derived in Isabelle/HOL. Particular emphasis is put on the optimized compilation of function applications leading to the side-calculi inferring e.g. strictness of functions. 
 
The derived rules were grouped and set-up as an instance of our generic, tactic-based translator for specifications to code.

title: On algorithmically checking whether a Hilbert series comes from a complete intersection
abstract: 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.

title: Robustness to Code and Data Deletion in Autocatalytic Quines
abstract: 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.