14817828
Argumentation-based abduction in disjunctive logic programming
Abstract In this paper, we propose an argumentation-based semantic framework, called DAS, for disjunctive logic programming. The basic idea is to translate a disjunctive logic program into an argumentation-theoretic framework. One unique feature of our proposed framework is to consider the disjunctions of negative literals as possible assumptions so as to represent incomplete information. In our framework, three semantics preferred disjunctive hypothesis (PDH), complete disjunctive hypothesis (CDH) and well-founded disjunctive hypothesis (WFDH) are defined by three kinds of acceptable hypotheses to represent credulous, moderate and skeptical reasoning in artificial intelligence (AI), respectively. Furthermore, our semantic framework can be extended to a wider class than that of disjunctive programs (called bi-disjunctive logic programs). In addition to being a first serious attempt in establishing an argumentation-theoretic framework for disjunctive logic programming, DAS integrates and naturally extends many key semantics, such as the minimal models, extended generalized closed world assumption (EGCWA), the well-founded model, and the disjunctive stable models. In particular, novel and interesting argumentation-theoretic characterizations of the EGCWA and the disjunctive stable semantics are shown. Thus the framework presented in this paper does not only provide a new way of performing argumentation (abduction) in disjunctive deductive databases, but also is a simple, intuitive and unifying semantic framework for disjunctive logic programming.
1885288
A Theory of Forgetting in Logic Programming
The study of forgetting for reasoning has attracted considerable attention in AI. However, much of the work on forgetting, and other related approaches such as independence, irrelevance and novelty, has been restricted to the classical logics. This paper describes a detailed theoretical investigation of the notion of forgetting in the context of logic programming. We first provide a semantic definition of forgetting under the answer sets for extended logic programs. We then discuss the desirable properties and some motivating examples. An important result of this study is an algorithm for computing the result of forgetting in a logic program. Furthermore, we present a modified version of the algorithm and show that the time complexity of the new algorithm is polynomial with respect to the size of the given logic program if the size of certain rules is fixed. We show how the proposed theory of forgetting can be used to characterize the logic program updates.
26247223
Combining Description Logic and Defeasible Logic for the Semantic Web
The importance of integrating rules and ontologies for the Semantic Web has been well addressed by many researchers. Defeasible Logic is a simple but efficient nonmonotonic language which can handle both defeasibility and priority. In this paper we propose a novel approach to combining Defeasible Logic with Description Logics by introducing the Description Defeasible Logic (DDL). DDL is similar to Defeasible Logic but it also contains queries to the Description Logic knowledge base. DDL allows nonmonotonic reasoning to be built on top of ontologies, and to a certain degree, allows ontologies to be built on top of nonmonotonic reasoning. We give some basic properties of DDL, one of which shows that DDL is a tractable language provided that the underlying Description Logic is tractable.
5228937
Merging and Aligning Ontologies in dl-Programs
The language of dl-programs is a latest effort in developing an expressive representation for Web-based ontologies. It allows to build answer set programming (ASP) on top of description logic and thus some attractive features of ASP can be employed in the design of the Semantic Web architecture. In this paper we first generalize dl-programs by allowing multiple knowledge bases and then accordingly, define the answer set semantics for the dl-programs. A novel technique called forgetting is developed in the setting of dl-programs and applied to ontology merging and aligning.
2316989
Observation-based Model for BDI-Agents
We present a new computational model of BDI-agents, called the observation-based BDI-model. The key point of this BDI-model is to express agents' beliefs, desires and intentions as a set of runs (computing paths), which is exactly a system in the interpreted system model, a well-known agent model due to Halpern and his colleagues. Our BDI-model is computationally grounded in that we are able to associate the BDI-agent model with a computer program, and formulas, involving agents' beliefs, desires (goals) and intentions, can be understood as properties of program computations. We present a sound and complete proof system with respect to our BDI-model and explore how symbolic model checking techniques can be applied to model checking BDI-agents. In order to make our BDI-model more flexible and practically realistic, we generalize it so that agents can have multiple sources of beliefs, goals and intentions.
1889167
An Extension to GCWA and Query Evaluation for Disjunctive Deductive Databases
We present a simple and intuitive extension GCWAG of the generalized closed world assumption (GCWA) from positive disjunctive deductive databases to general disjunctive deductive databases (with default negation). This semantics is defined in terms of unfounded sets and possesses an argumentation-theoretic characterization. We also provide a top-down procedure for GCWAG, which is sound and complete with respect to GCWAG. We investigate two query evaluation methods for GCWAG: database partition, and database splitting. The basic idea of these methods is to divide the original deductive database into several smaller sub-databases and the query evaluation in the original database is transformed into the problem of query evaluation in smaller or simplified components. We prove that these two methods of query evaluation are all sound with respect to GCWAG.
36512646
A Peer-to-Peer Communication System
The demand of communicating anywhere, anytime on any device is growing with the development of modern information technology. Current instant messaging services enable people to be aware of each other's presence and to exchange text information. However, almost all of these services are based on client/server architecture. If servers crash, all connections are lost. As an alternative, peer-to-peer architecture basically relies on clients, but existing systems usually emphasize sharing of computing resources and files. In this paper, we propose a peer-to-peer communication system, which combines the advantages of instant messaging services and peer-to-peer networking. In the system, in addition to being aware of each other's presence, users can simultaneously attend multiple multimedia meetings with each meeting allowing multiple attendees. Users have full control over the exchange of real-time text/voice/video information in these meetings.
11784167
An access control language for web services
This paper presents an approach for formally specifying and enforcing security policies on web service implementations. Networked services in general, and web services in particular, require extensive amounts of code to ensure that clients respect site-integrity constraints. We provide a language by which these constraints can be expressed and enforced automatically, portably and efficiently. Security policies in our system are specified in a language based on temporal logic, and are processed by an enforcement engine to yield site and platform-specific access control code. This code is integrated with a web server and platform-specific libraries to enforce the specified policy on a given web service. Our approach decouples the security policy specification from service implementations, provides a mandatory access control model for web services, and achieves good performance. We show that up to 22% of the code in a traditional web service module is dedicated to security checking functionality, including checks for client sequencing and parameter validation. We show that our prototype language implementation, WebGuard, enables web programmers to significantly reduce the amount of security checking code they need to develop manually. The quality of the code generated by WebGuard from formal policy specifications is competitive with the latency of handcrafted code to within a few percent.
304685
Anonymizing sequential releases
An organization makes a new release as new information become available, releases a tailored view for each data request, releases sensitive information and identifying information separately. The availability of related releases sharpens the identification of individuals by a global quasi-identifier consisting of attributes from related releases. Since it is not an option to anonymize previously released data, the current release must be anonymized to ensure that a global quasi-identifier is not effective for identification. In this paper, we study the sequential anonymization problem under this assumption. A key question is how to anonymize the current release so that it cannot be linked to previous releases yet remains useful for its own release purpose. We introduce the lossy join, a negative property in relational database design, as a way to hide the join relationship among releases, and propose a scalable and practical solution.
38950979
Behavior Profiling of Email
This paper describes the forensic and intelligence analysis capabilities of the Email Mining Toolkit (EMT) under development at the Columbia Intrusion Detection (IDS) Lab. EMT provides the means of loading, parsing and analyzing email logs, including content, in a wide range of formats. Many tools and techniques have been available from the fields of Information Retrieval (IR) and Natural Language Processing (NLP) for analyzing documents of various sorts, including emails. EMT, however, extends these kinds of analyses with an entirely new set of analyses that model "user behavior". EMT thus models the behavior of individual user email accounts, or groups of accounts, including the "social cliques" revealed by a user's email behavior.
39282722
Parallel Multilevel Sparse Approximate Inverse Preconditioners in Large Sparse Matrix Computations