Lingzhong Zhao

A Family of Dynamic Description Logics for Representing and Reasoning About Actions

Description logics provide powerful languages for representing and reasoning about knowledge of static application domains. The main strength of description logics is that they offer considerable expressive power going far beyond propositional logic, while reasoning is still decidable. There is a demand to bring the power and character of description logics into the description and reasoning of dynamic application domains which are characterized by actions. In this paper, based on a combination of the propositional dynamic logic PDL, a family of description logics and an action formalism constructed over description logics, we propose a family of dynamic description logics DDL(X@) for representing and reasoning about actions, where X represents well-studied description logics ranging from the to the , and X@ denotes the extension of X with the @ constructor. The representation power of DDL(X@) is reflected in four aspects. Firstly, the static knowledge of application domains is represented as RBoxes and acyclic TBoxes of the description logic X. Secondly, the states of the world and the pre-conditions of atomic actions are described by ABox assertions of the description logic X@, and the post-conditions of atomic actions are described by primitive literals of X@. Thirdly, starting with atomic actions and ABox assertions of X@, complex actions are constructed with regular program constructors of PDL, so that various control structures on actions such as the “Sequence”, “Choice”, “Any-Order”, “Iterate”, “If-Then-Else”, “Repeat-While” and “Repeat-Until” can be represented. Finally, both atomic actions and complex actions are used as modal operators for the construction of formulas, so that many properties on actions can be explicitly stated by formulas. A tableau-algorithm is provided for deciding the satisfiability of DDL(X@)-formulas; based on this algorithm, reasoning tasks such as the realizability, executability and projection of actions can be effectively carried out. As a result, DDL(X@) not only offers considerable expressive power going beyond many action formalisms which are propositional, but also provides decidable reasoning services for actions described by it.

Using ASP for knowledge management with user authorization

Unlike conventional rule based knowledge bases (KBs) that support monotonic reasoning, a key correctness issue, i.e. the correctness of a sub-KB with respect to the full KB, arises when using a KB represented by non-monotonic reasoning languages such as Answer Set Programming (ASP). Since a user may have rights to access only a subset of a KB, the non-monotonic nature of ASP may cause the occurrence of consequences, which are erroneous in the sense that the consequences are not reasonable in the full KB. This paper proposes an approach dealing with the problem. The main idea is to let the usage of Closed World Assumptions (CWAs) for literals in a KB satisfy certain constraints. Two kinds of access right propositions are created, rule retrieval right propositions to control the access to rules, and CWA right propositions to control the usage of CWAs for literals. Based on these right propositions, this paper first defines an algorithm for translating an original KB into a KB tagged by right propositions, and then discusses the right dependency in a KB and proposes methods for checking and obtaining a set of rights that is closed under a set of dependency rules. Finally, several results on the correctness of a set of rights in a KB are presented, which serve as guidelines for the correct use of a KB. As an example, a KB of illness-related financial support for teachers of a university is presented to illustrate the application of our approach.

An integer programming method for constructing tightly coupled VLSI subarrays

Minimizing the interconnection length between the processing elements (PEs) of VLSI arrays is beneficial to reduce the capacitance, power dissipation and dynamic communication cost. In this paper, a novel method, based on integer programming, for constructing tightly-coupled subarrays from the degradable VLSI arrays is presented, such that the target array has the minimum interconnection length. Compared with the state-of-the-art algorithms, the proposed method can guarantee that the interconnection length of the target array is minimum in row and column directions simultaneously. The performances of the proposed method are compared with previous studies and it indicates that the proposed method achieves better results in terms of total interconnection length.

Optimal Reconfiguration of High-Performance VLSI Subarrays with Network Flow

A two-dimensional mesh-connected processor array is an extensively investigated architecture used in parallel processing. Massive studies have addressed the use of reconfiguration algorithms for the processor arrays with faults. However, the subarray generated by previous algorithms contains a large number of long interconnects, which in turn leads to more communication costs, capacitance and dynamic power dissipation. In this paper, we propose novel techniques, making use of the idea of network flow, to construct the high-performance subarray, which has the minimum number of long interconnects. First, we construct a network flow model according to the host array under a specific constraint. Second, we show that the reconfiguration problem of high-performance subarray can be optimally solved in polynomial time by using efficient minimum-cost flow algorithms. Finally, we prove that the geometric properties of the resulted subarray meet the system requirements. Simulations based on several random and clustered fault scenarios clearly reveal the advantage of the proposed technique for reducing the number of long interconnects. It is shown that, for a host array of size 512 × 512, the number of long interconnects in the subarray can be reduced by up to 70.05 percent for clustered faults and by up to 55.28 percent for random faults with density of 1 percent as compared to the-state-of-the-art.

Automatic Construction of Complete Abstraction by Abstract Interpretation

Abstraction plays a fundamental role in combating state-space explosion in model checking. Firstly, we study how to abstract models of mu-calculus and derive abstractions that are sound, and apply them to abstracting Kripke structures. However, a lack of completeness in the abstract interpretation leads to spurious counterexamples in the abstract model checking. In order to eliminate spurious counterexamples, the paper describes a method for minimally making abstract interpretations complete, and this refined complete abstract domain always exists.

A novel test case generation method for prolog programs based on call patterns semantics

A natural way to generate test cases for a Prolog program is to view the call patterns of the procedures in the program as an implicit representation of the control flow graph (CFG) of the program. This paper explores the idea by proposing a call patterns-based test case generation method, where a set of call patterns or computed answers is used to describe the paths in a CFG. With a constraint-based call patterns semantics, this method is formalized. Through the use of a proper constraints solver, we can generate test cases automatically from the sets of constraints. This method can be based on any approximation of the call patterns semantics. So compared with traditional CFG-based test case generation, the method is more flexible and can be easily adapted to meet the requirements of a tester expressed by the approximation of the call patterns semantics we use.

An Improved Reconfiguration Algorithm for VLSI Arrays with A-Star

This paper describes a novel technique to speed up the reconfiguration for the VLSI arrays. We propose an efficient algorithm based on A-star algorithm for accelerating reconfiguration of the power efficient VLSI processor subarrays to meet the real-time constraints and lower power consumption of the embedded systems. The proposed algorithm treats the problem of constructing a local optimal logical column that has the minimum number of long interconnects as a shortest path problem. Then the local optimal column can be constructed by utilizing A-star algorithm with appropriate heuristic strategy. The proposed algorithm greatly reduces the number of visits to the fault-free PEs for constructing a local optimal logical column and effectively decreases the reconfiguration running time. Experimental results show that the computation time can be improved by more than 38.64 % for a \(128 \times 128\) host array with fault density of 20 %, without loss of harvest.

A Data-Driven Service Creation Approach for End-Users

Spurred by Web technologies and service computing paradigm, more and more Web services have been delivered via standardized interfaces on the Internet. Mashup is exactly an enabling technology for end-users to combine these services into applications. However, there are some issues of end-user service development with mashup techniques. It not only requires users that develop application logics equipped with more or less programming skills, but also lacks a lightweight mashup model and systematic development approach in the existing mashup tools. To address these issues, we propose a data-driven service creation approach to facilitate application development and deployment. In the approach, we propose the service data model (SDM) for adaptation of heterogeneous Web services, the service relation model (SRM) for representation and refinement of data interaction between services, and the service process graph (SPG) for describing business logics of mashup applications. We develop an IFrame implementation for SDM that can facilitate service providers to wrap heterogeneous Web services in a unified way and display a visual element for the service. Meanwhile, we implement a pipeline as an intuitive form of SRM that can be used by end-users to develop business logic more effectively. To adapt the dynamic application scenarios, we also construct an event-driven execution mechanism for SPG. A lightweight service creation environment is then implemented to support end-users to develop applications in a simulative way, and a corresponding development methodology is introduced for this tool. Finally, the end-user evaluation and performance evaluation are conducted to evaluate our platform.

Semantic Web Service Composition: From OWL-S to Answer Set Programming

This paper presents a method that adapting planning description to bring the semantic information into play for service composition through action language C. It shows how service descriptions can be expressed by preconditions and effects and the action language C provides a richer syntax and semantic for complex service descriptions. We also presents the algorithm of translating semantic web service described by OWL-S to action language C. Thanks to the structured description and the powerful expression of C, we only consider the initial Situation and the desired goal ignoring details of transition and planning. At last we use satisfiability planning to solve the planning problem by translating the action language into disjunctive logic program.

An ASP Based Solution to Mechanical Assembly Sequence Planning

Declarative methods for planning problems admit highly efficient and understandable problem description. Mechanical Assembly Sequence Planning (MASP) is a kind of planning problem that is difficult and of great importance in industrial production. This paper proposes a novel Answer Set Programming (ASP) based declarative solution to MASP. Given a CAD model of an assembly, all assembly knowledge and necessary constraints can be produced automatically. With the answer set solver DLV all assembly sequences could be generated. And thanks to the declarativeness of the method the representation efficiency and time efficiency of the method can be improved separately.