This paper revisits a problem that was identified by Kramer and Magee: placing a system in a consistent state before and after runtime changes [16]. We show that their notion of quiescence as a necessary and sufficien...
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ISBN:
(纸本)0769523544
This paper revisits a problem that was identified by Kramer and Magee: placing a system in a consistent state before and after runtime changes [16]. We show that their notion of quiescence as a necessary and sufficient condition for safe runtime changes is too strict and violates the black-box design principle. We introduce a weaker condition, tranquility;easier to obtain, less disruptive for the system and still sufficient to ensure application consistency. We also present an implementation of this concept in a component middleware platform.
The proceedings contain 12 papers. The topics discussed include: forgetting in managing rules and ontologies;query evaluation and optimization in the semantic web;dlvhex: a tool for semantic-web reasoning under the an...
The proceedings contain 12 papers. The topics discussed include: forgetting in managing rules and ontologies;query evaluation and optimization in the semantic web;dlvhex: a tool for semantic-web reasoning under the answer-set semantics;G-hybrid knowledge bases;intelligent agents that reason about web services: a logicprogramming approach;efficient web service discovery and composition using constraint logicprogramming;policy-based reasoning for smart web service interaction;towards automated web service composition with the abductive event calculus;modeling, verifying and reasoning about web services;a RuleML syntax for answer-set programming;prolog execution engines for description logic reasoners;and applying prolog to semantic web ontologies and rules: moving toward description logic programs.
One of the main promises of aspect-oriented programming (AOP) is to promote improved modularization of crosscutting concerns, thereby enhancing the software stability in the presence of changes. This paper presents a ...
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ISBN:
(纸本)0769523544
One of the main promises of aspect-oriented programming (AOP) is to promote improved modularization of crosscutting concerns, thereby enhancing the software stability in the presence of changes. This paper presents a quantitative study that assesses the positive and negative effects of AOP on typical maintenance activities of a Web information system. The study consists of a systematic comparison between the object-oriented and the aspect-oriented versions of the same application in order to assess to what extent each solution provides maintainable software decompositions. Our analysis was driven by fundamental modularity attributes, such as coupling, cohesion, conciseness, and separation of concerns. We have found that the aspect-oriented design has exhibited superior stability and reusability through the changes, as it has resulted in fewer lines of code, improved separation of concerns, weaker coupling, and lower intra-component complexity.
Rule-based specifications in Datalog are used in a number of application areas, such as configuration management, access control and trust management, decision making, etc. However, rules sets are typically hard to ma...
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ISBN:
(纸本)3540366350
Rule-based specifications in Datalog are used in a number of application areas, such as configuration management, access control and trust management, decision making, etc. However, rules sets are typically hard to maintain;the rules often interact in subtle ways, making them difficult to understand and reason about. This has impeded the wide-spread adoption of rule-based computing. This paper describes the design and implementation of XcelLog, a deductive spreadsheet system (DSS), that permits users to specify and maintain Datalog rules using the popular and easy-to-use spreadsheet interface. The driving idea underlying the system is to treat sets as the fundamental data type and rules as specifying relationships among sets, and use the spreadsheet metaphor to create and view the materialized sets. The fundamental feature that makes XcelLog suitable even for non-programmers is that the user mainly sees the effect of the rules;when rules or basic facts change, the user sees the impact of the change immediately. This enables the user to gain confidence in the rules and their modification, and also experiment with what-if scenarios without any programming. XcelLog is implemented as an add-in to Excel with XSB serving as the rule engine for evaluating Datalog specifications. Preliminary experience with using XcelLog indicates that it is indeed feasible to combine the power of rule-based computing and the elegance and simplicity of the spreadsheet metaphor, so that end users can encode and maintain rule bases with little or no programming.
A description in the Jacobs and Langen domain is a set of sharing groups where each sharing group is a set of program variables. The presence of a sharing group in a description indicates that all the variables in the...
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ISBN:
(纸本)3540366350
A description in the Jacobs and Langen domain is a set of sharing groups where each sharing group is a set of program variables. The presence of a sharing group in a description indicates that all the variables in the group can be bound to terms that contain a common variable. The expressiveness of the domain, alas, is compromised by its intractability. Not only are descriptions potentially exponential in size, but abstract unification is formulated in terms of an operation, called closure under union, that is also exponential. This paper shows how abstract unification can be reformulated so that closures can be collapsed in two senses. Firstly, one closure operation can be folded into another so as to reduce the total number of closures that need to be computed. Secondly, the remaining closures can be applied to smaller descriptions. Therefore, although the operation remains exponential, the overhead of closure calculation is reduced. Experimental evaluation suggests that the cost of analysis can be substantially reduced by collapsing closures.
We introduce a formal proof system based on tableau methods for analyzing computations made in Answer Set programming (ASP). Our approach furnishes declarative and fine-grained instruments for characterizing operation...
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ISBN:
(纸本)3540366350
We introduce a formal proof system based on tableau methods for analyzing computations made in Answer Set programming (ASP). Our approach furnishes declarative and fine-grained instruments for characterizing operations as well as strategies of ASP-solvers. First, the granulation is detailed enough to capture the variety of propagation and choice operations of algorithms used for ASP;this also includes SAT-based approaches. Second, it is general enough to encompass the various strategies pursued by existing ASP-solvers. This provides us with a uniform framework for identifying and comparing fundamental properties of algorithms. Third, the approach allows us to investigate the proof complexity of algorithms for ASP, depending on choice operations. We show that exponentially different best-case computations can be obtained for different ASP-solvers. Finally, our approach is flexible enough to integrate new inference patterns, so to study their relation to existing ones. As a result, we obtain a novel approach to unfounded set handling based on loops, being applicable to non-SAT-based solvers. Furthermore, we identify backward propagation operations for unfounded sets.
Coupling in software has been linked with maintainability and existing metrics are used as predictors of external software quality attributes such as fault-proneness, impact analysis, ripple effects of changes, change...
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ISBN:
(纸本)0769523544
Coupling in software has been linked with maintainability and existing metrics are used as predictors of external software quality attributes such as fault-proneness, impact analysis, ripple effects of changes, changeability, etc. Many coupling measures for object-oriented (OO) software have been proposed, each of them capturing specific dimensions of coupling. This paper presents a new set of coupling measures for OO systems-named conceptual coupling, based on the semantic information obtained from the source code, encoded in identifiers and comments. A case study on open source software systems is performed to compare the new measures with existing structural coupling measures. The case study shows that the conceptual coupling captures new dimensions of coupling, which are not captured by existing coupling measures;hence it can be used to complement the existing metrics.
Constraint propagation algorithms implement logical inference. For efficiency, it is essential to control whether and in what order basic inference steps are taken. We provide a high-level framework that clearly diffe...
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