Towards the Adaptive Web Using Metadata Evolution

The evolution of Web information is of utmost impor tance in the design of good Web Information Systems applications. New emerging para digms, like the Semantic Web, use ontologies for describing metadata and are defined, i part to aid in Web evolution. In this chapter, we survey techniques for ontology evolutio n. After identifying the different kinds of evolution the Web is confronted with, we detail the various existing languages and techniques devoted to Web data evolution, with particular atte ntion to Semantic Web concepts, and how these languages and techniques can be adapted to ev olving data in order to improve the quality of Web Information Systems applications. Towards the Adaptive Web using Metadata Evolution When we consider the evolution of the World Wide We b (WWW) and its development over the last decade, we can see drastic changes ha v taken place. Originally, the Web was built on static HTML documents and used as experimental c ommunication means for specific communities in educational institutions and governm e t defence agencies. With its ever increasing popularity, the WWW is now the largest r esource of information in the world. As such, it contains either durable or volatile inform ation that needs to be maintained easily and often with predefined time delays. For example, thi s is the case for day-to-day news diffusion. The emergence of new paradigms like the Semantic We b (B rners-Lee, Hendler, & Lassila, 2001) has further intensified the evolution of the W b. Since Semantic Web has the ability to make Web information machines understandable, it co rrelates to an improvement in quality of Web content and Web services and the result unloads user of tedious search tasks. These changes are accompanied by the manifestation of new application families such as Web Information System (WIS) applications. WIS appl ications are developed based on Web content and consequently must adapt to its evolutio n. C nsider, for example, a tourism application for helping users prepare their holiday s. If the company introduces a new kind of vacation (e.g., social holidays for elderly people) then the application needs to be maintained in order to cope with the evolution of this domain. Th e development of WIS applications is not an easy task since it is difficult to clearly catch th e semantics of actual Web content, which in turn limits the retrieval of relevant Web information (G uelfi & Pruski, 2006). Parallel to this development, the use of metadata t o drive the advancement of Web-based applications has proven to be a very promising fiel d of research (“Web Engineering: Principles and Techniques,” 2005) and we believe that the use of metadata can improve the quality of WIS applications. Metadata is useful to describe Web re sources in a structured and precise way. It can be used, for instance, to describe the content of t ourism resources in our application example. Consequently, languages are needed to define metada ta nd techniques are required for the metadata to smoothly follow the evolution of the de scribed resource. To this end, the Semantic Web paradigm can be the key to success. It consists in using ontologies (Gruber, 1993) to define the semantics of a particular domain and then uses the vocabulary contained in these ontologies as metadata to annotate Web content. In this context, many ontology languages have been int sively studied in the literature (Antoniou & van Harmelen, 2004; Charlet, Laublet, & Reynaud, 2004). Although they provide basic modelling features, they do not offer enough properties to design and maintain ontologies that have the ability to evolve over time. Static o ntologies designed with existing languages seem to be unsuitable for today’s dynamic Web and what i t requires instead are “dynamic” ones, which are built using new kinds of languages and te chniques in order to give them the property of being evolvable over time according to modificat ion of Web content. Since these new languages and techniques will have an important imp act on Web-based applications and mainly WIS applications, we need to carefully identify the different kinds of evolution that can affect Web content and to evaluate the current capabilitie s of existing languages. In this chapter we propose to survey state-of-the-a rt dynamic ontology languages and techniques. This study also contains notes concerni ng knowledge evolution in other paradigms connected to the WWW, like reactivity (Alferes et a l., 2004) and Adaptive Hypermedia Systems (AHS) (Brusilovsky, 2001), both of which have eleme nts that should be integrated in the development of advanced WIS applications. Such adap t tion techniques can be used, for example, to adapt the presentation of content to us ers. Imagine our tourism application able to display in bold red font a particular offer, like a fee reduction on a particular service. In order to cope with various kinds of Web content evolution, w e ill provide some elements regarding the improvement of these languages. Based on our survey and the proposals we make, we believe that it will be easier to understand the impact of languages and technologies on the quality of future WIS applications. We first discuss existing types of evolution impact ing the Web as well as related work in the field of languages and techniques for Web data evolution. Dealing with the evolutionary aspect of Web content, two important research field s stand out: reactivity and AHS. Within the framework of reactivity, several interesting EventConditions-Actions (ECA) languages have been proposed to not only make Semantic Web concept s r active but also classic web sites. AHS is a young research field that we will talk about i n detail since it takes into account knowledge evolution and introduces user adaptation, which is important for future versions of the Web. Following this, we discuss related work in the fiel d of languages and techniques for ontology evolution of the Semantic Web. Although a set of standards have being established by the World Wide Web Consortium (W3C) and intensively studied in literature, new ones are under investigation. In this section we will presen t these emergent languages and techniques. We will briefly introduce standards like Web Ontology Language (OWL) and focus on the description of new languages like dOWL and the pres entation of methodologies that have been proposed to deal with ontology evolution. We also p r pose some perspectives about the extension of the studied languages with respect to on logy evolution. The next section discusses the impact of the concep ts we have presented on the quality of WIS applications. Based on our remarks, we illustra te what has to be done to increase the quality of WIS applications at each stage of its lifecycle, i. from design to runtime, mainly by taking into account user preferences, experiences and beha viour. Finally, we wrap up with concluding remarks. WEB DATA EVOLUTION: PRINCIPLES AND TECHNIQUES