Vol.11 No.2 June 1, 2012

A Non-monotonic Expressiveness Extension on the Semantic Web Rule Language (pp093-118)
        Jose M. Alcaraz Calero, Andres Munoz, Gregorio Martinez, Juan A. Botia, and Antonio F. Gomez Skarmeta
SWRL (Semantic Web Rule Language) extends OWL syntax and semantics by enabling the description of Horn-like rules. However, the current SWRL specification lacks support for, among others, negative expressions, missing values and priority relationships between rules, which are frequently needed when modeling realistic scenarios. This paper motivates the necessity of surpassing some of these problems and provides an extension over the original SWRL aimed to define more expressive rules. Hence, the following four operators have been added to SWRL: $Not$ operator (i.e., classical negation) to express negative facts; $NotExists$ quantifier to ask for missing facts in the knowledge base (when used in the antecedent of the rule) and remove facts (when used in the consequent); $Dominance$ operator to establish priorities among rules; and $Mutex$ operator to establish exclusions during rule executions. The syntax and semantics of these four operators are described in this proposal. Moreover, the non-monotonicity added to the rule-based inference process by means of such elements is also explained. An implementation of the four operators has been developed as a plug-in for the Jena generic rule engine, which enables the execution of Horn-like rules, together with a parser to translate SWRL rules to the Jena specific rule language. Finally, the proposed SWRL extension and its implementation have been validated in a real scenario centered on call forwarding management in an intelligent building.

A Caching Mechanism for QoS-aware Service Composition (pp119-130)
        Quanwang Wu, Qingsheng Zhu, and Peng Li
Web service composition enables seamless and dynamic integration of business applications on the web. With the growing number of web services that provide the same functionality but differ in quality parameters, the QoS-aware service composition becomes a decision problem on which component services should be selected such that the quality of the composite service is optimized and user preference is satisfied. In this paper, we presented a caching mechanism for this problem, which can be complementary to most of current approaches to enhance the efficiency. We evaluate our approach experimentally using a real QoS dataset and it shows a significant impact in reducing the computing time.

MAXLCA: A New Query Semantic Model for XML Keyword Search (pp131-145)
        Ning Gao, Zhu-Hong Deng, Jia-Jian Jiang, and Hang Yu
Keyword search enables web users to easily access XML data without understanding the complex data schemas. However, the ambiguity of keyword search makes it arduous to select qualified data nodes matching keywords. To address this challenge in XML datasets whose documents have a relatively low average size, we present a new keyword query semantic model: MAXimal Lowest Common Ancestor (MAXLCA). MAXLCA can effectively avoid false negative problem observed in ELCA, SLCA and XSeek. Furthermore, we construct an algorithm GMAX for MAXLCA-based queries that is proved efficient in evaluations. Experiments on INEX show that the search engine using MAXLCA and GMAX outperforms in all three comparative criteria: effective, efficient and processing scalability.

A Novel Approach for Service Performance Analysis and Forecast (pp146-176)
        Sid Kargupta and Sue Black
This research establishes a predictive model to forecast the impact on service performance for changes to the underlying activities of the service’s components. It deduces a relational model between a service’s performance, its application component latencies and the request load. The major challenge the IT industry is currently facing with the cost associated with repeated performance testing to modify live systems has been addressed. The notion of implicit Operation Impedance gradient (I_G) and Operation Potential (V) in Service Provider-Consumer contracts has been introduced. This work establishes that ‘I_G’, which impacts the overall Operation Performance (P), is influenced by the underlying application components’ activities in distinct patterns. A high-level runtime abstract model is empirically deduced between ‘I_G’, ‘V’ and ‘P’ by applying established mathematical techniques. Model based indicative values of some features are computed and associated with the actual empirical values of other features against various system configurations. Appropriate regression types are applied to enable trend extrapolation/interpolation. The datasets affirmed effectiveness of the model to assess impact of modifications to the underlying application components on the operation’s performance without repetitive full scale external performance/benchmark testing. This also enables fine tuning of application components to retrofit prescribed Quality of Services. To address real life applications, this paper describes a Matrix based technique used for the assessment of changes to multiple types of application component activities simultaneously. The method of calibrating the Matrix aided model has also been discussed briefly.

Book Review:

On Linked Data – Evolving the Web into a Global Data Space, Authored by Tom Heath and Christian Bizer (pp177-178)
        Bebo White

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