The Web Verification Service WebVerdi-M

Lecture Notes in Computer Science, 2009

This paper presents a Rewriting Logic framework that formalizes the interactions between Web servers and Web browsers through a communicating protocol abstracting HTTP. The proposed framework includes a scripting language that is powerful enough to model the dynamics of complex Web applications by encompassing the main features of the most popular Web scripting languages (e.g. PHP, ASP, Java Servlets). We also provide a detailed characterization of browser actions (e.g. forward/backward navigation, page refresh, and new window/tab openings) via rewrite rules, and show how our models can be naturally model-checked by using the Linear Temporal Logic of Rewriting (LTLR), which is a Linear Temporal Logic specifically designed for model-checking rewrite theories. Our formalization is particularly suitable for verification purposes, since it allows one to perform in-depth analyses of many subtle aspects related to Web interaction. Finally, the framework has been completely implemented in Maude, and we report on some successful experiments that we conducted by using the Maude LTLR model-checker.

Lecture Notes in Computer Science, 2007

We present the CIFFWEB system, an innovative tool for the verification of web sites, relying upon abductive logic programming. The system allows the user to define rules that a web site should fulfill by using (a fragment of) the query language Xcerpt. The rules are translated into abductive logic programs with constraints and their fulfillment is checked through the CIFF abductive proof procedure.

2008 Eighth International Conference on Web Engineering, 2008

Quality assurance of Web applications is usually an informal process. Meanwhile, formal methods have been proven to be reliable means for the specification, verification, and testing of systems. However, the use of these methods requires learning their mathematical foundations, including temporal logics. Specifying properties using temporal logic is often complicated even to experts, while it is a daunting and error prone task for non-expert users. To assist web developers and testers in formally specifying web related properties, we elaborate a library of web specification patterns. The current version of the library of 119 functional and non-functional patterns is a result of scrutinizing various resources in the field of quality assurance of Web Applications, which characterize successful web application using a set of standardized attributes.

2006

The development and maintenance of Web sites are difficult tasks. To maintain the consistency of ever-larger, complex Web sites, Web administrators need effective mechanisms that assist them in fixing every possible inconsistency. In this paper, we present a novel methodology for semi-automatically repairing faulty Web sites which can be integrated on top of an existing rewriting-based verification technique developed in a previous work. Starting from a categorization of the kinds of errors that can be found during the Web verification activities, we formulate a stepwise transformation procedure that achieves correctness and completeness of the Web site w.r.t. its formal specification while respecting the structure of the document (e.g. the schema of an XML document). Finally, we shortly describe a prototype implementation of the repairing tool which we used for an experimental evaluation of our method.

2008

We present the CIFFWEB system, an innovative tool for the verification and repair of web sites, relying upon abductive logic programming. The system allows the user to define rules that a web site should fulfill and uses abductive reasoning for checking their fulfillment and, if needed, for suggesting repairs to those (parts of the) web sites responsible for violating them. The rules are expressed by using (a fragment of) the rule-based semi-structured query language Xcerpt. Then, we give a mapping from Xcerpt rules into abductive logic programs, that can be executed by means of the general-purpose CIFF proof procedure for abductive logic programming with constraints. Finally, we illustrate how a similar technique can be used effectively for actually repairing errors in web sites. The CIFFWEB system is a prototype system composed of (1) the CIFF System 4.0 and (2) a translator which, given checking rules expressed in Xcerpt and XML/XHTML pages, computes an abductive logic program with constraints that can be run under CIFF 4.0.

Electronic Notes in Theoretical Computer Science, 2008

In this paper, a model for websites is presented. The model is well-suited for the formal verification of dynamic as well as static properties of the system. A website is defined as a collection of web pages which are semantically connected in some way. External web pages (which are related pages not belonging to the website) are treated as the environment of the system. We also present the logic which is used to specify properties of websites, and illustrate the kinds of properties that can be specified and verified by using a model-checking tool on the system. In this setting, we discuss some interesting properties which often need to be checked when designing websites. We have encoded the model using the specification language Maude which allows us to use the Maude model-checking tool.

Springer eBooks, 2001

Web design is an inherently error-prone process. To help with the detection of errors in the structure and connectivity of Web pages, we propose to apply model-checking techniques to the analysis of the World Wide Web. Model checking the Web is different in many respects from ordinary model checking of system models, since the Kripke structure of the Web is not known in advance, but can only be explored in a gradual fashion. In particular, the model-checking algorithms cannot be phrased in ordinary µ-calculus, since some operations, such as the computation of sets of predecessor Web pages and the computations of greatest fixpoints, are not possible on the Web. We introduce constructive µ-calculus, a fixpoint calculus similar to µ-calculus, but whose formulas can be effectively evaluated over the Web; and we show that its expressive power is very close to that of ordinary µ-calculus. Constructive µ-calculus can be used not only for phrasing Web model-checking algorithms, but also for the analysis of systems having a large, irregular state space that can be only gradually explored, such as software systems. On the basis of these ideas, we have implemented the Web model checker MCWEB, and we describe some of the issues that arose in its implementation, as well as the type of errors that it was able to find.

2009

WWV'09 provided a common forum for researchers from the communities of Rule-based programming, Automated Software Engineering, and Web-oriented research, in order to facilitate the cross-fertilization and the advancement of hybrid methods that combine the three areas. The Program Committee of WWV'09 collected three reviews for each paper and held an electronic discussion during April 2009 which has led to the selection of 10 regular papers. In addition to the selected papers, the scientific program included two invited lectures by François Bry from the Ludwig Maximilian University of Munich (Germany), and Axel Polleres from the National University of Ireland, Galway (Ireland). We would like to thank them for having accepted our invitation. We would also like to thank all the members of the Program Committee and all the referees for their careful work in the review and selection process. Many thanks to all authors who submitted papers and to all conference participants. We gratefully acknowledge all the institutions and corporations who have supported this event.

Lecture Notes in Computer Science, 2010

Web-TLR is a software tool designed for model-checking Web applications which is based on rewriting logic. Web applications are expressed as rewrite theories which can be formally verified by using the Maude built-in LTLR model-checker. Web-TLR is equipped with a userfriendly, graphical Web interface that shields the user from unnecessary information. Whenever a property is refuted, an interactive slideshow is generated that allows the user to visually reproduce, step by step, the erroneous navigation trace that underlies the failing model checking computation. This provides deep insight into the system behavior, which helps to debug Web applications.

Keeping XML data in a consistent state w.r.t. both structure and content is a burdensome task. To maintain the consistency of ever-larger, complex XML repositories, suitable mechanisms that are able to fix every possible inconsistency are needed. In this article, we present a methodology for semi-automatically repairing faulty XML repositories that can be integrated on top of an existing rewriting-based verification engine. As a formal basis for representing consistency criteria, we use a rule-based description formalism that is realized in the language Maude. Then, starting from a categorization of the kinds of errors that can be found during the verification process, we formulate a stepwise transformation procedure that achieves correctness and completeness of the XML repository w.r.t. its Maude formal specification while strictly observing the structure of the XML documents. With the aim of increasing the level of automation of our repair methodology, we also define two correction strategies and two completion strategies that reduce either the amount of information to be changed or the number of repair actions to be executed in order to deliver an XML repository that is both correct and complete. Finally, we describe a prototype implementation of the repairing tool, which we use for an experimental evaluation of our method with good results. the aim of improving Web applications by cleaning up syntax, reorganizing frames, or updating to new standards. The work in [24] defines a rule-based approach to XML processing and Web reasoning that uses an extension of logic programming using unranked signatures (flexible arity, i.e., variadic symbols) and advanced rule-based programming features for hedge (aka unranked term sequence) transformations, strategies, and regular constraints. A Rewriting Logic approach to the formal specification and verification of dynamic Web applications can be found in .