P Peter Barna

Hera: development of semantic web information systems

As a consequence of the success of the Web, methodologies for information system development need to consider systems that use the Web paradigm. These Web Information Systems (WIS) use Web technologies to retrieve information from the Web and to deliver information in a Web presentation to the users. Hera is a model-driven methodology supporting WIS design, focusing on the processes of integration, data retrieval, and presentation generation. Integration and data retrieval gather from Web sources the data that composes the result of a user query. Presentation generation produces theWeb or hypermedia presentation format for the query result, such that the presentation and specifically its navigation suits the users browser. We show how in Hera all these processes lead to data transformations based on RDF(S) models. Proving the value of RDF(S) for WIS design, we pave the way for the development of Semantic Web Information Systems.

RAL: an algebra for querying RDF

To make the World Wide Web machine-understandable there is a strong demand both for languages describing metadata and for languages querying metadata. The Resource Description Framework (RDF), a language proposed by W3C, can be used for describing metadata about (Web) resources. RDF Schema (RDFS) extends RDF by providing means for creating application specific vocabularies (ontologies). While the two above languages are widely acknowledged as a standard means for describing Web metadata, a standardized language for querying RDF metadata is still an open issue. Research groups coming both from industry and academia are presently involved in proposing several RDF query languages. Due to the lack of an RDF algebra such query languages use APIs to describe their semantics and optimization issues are mostly neglected. This paper proposes RAL (an RDF algebra) as a reference mathematical study for RDF query languages and for performing RDF query optimization. We define the data model, we present the operators to manipulate the data, and we address the application of RAL for query optimization. RAL includes: extraction operators to retrieve the needed resources from the input RDF model, loop operators to support repetition, and construction operators to build the resulting RDF model.

Engineering the Presentation Layer of Adaptable Web Information Systems

Engineering adaptable Web Information Systems (WIS) requires systematic design models and specification frameworks. A complete model-driven methodology like Hera distinguishes between the conceptual, navigational, and presentational aspects of WIS design and identifies different adaptation “hot-spots” in each design step. This paper concentrates on adaptation in the presentation layer and combines the modeling power of Hera with the versatile presentation capabilities of the AMACONT project. After discussing different aspects of presentation layer adaptation, the layout manager mechanism of AMACONT for describing the adaptable layout of ubiquitous Web presentations is introduced. Then the RDFS-based Hera schema for presentation models is presented, allowing to assign AMACONT layout descriptors to Hera slices. According to this formalization, Hera application model instances are automatically transformed to a component-based AMACONT implementation that can be adjusted to different end devices and output formats. The XML-based transformation process is explained in detail, and the resulting methodology is exemplified by a prototype application.

Adaptation and reuse in designing Web information systems

The increasing number of requirements for a Web information system asks for an engineered process in designing such a system. In this paper we focus on two of these requirements: presentation adaptation based on user preferences/device capabilities and reusability of the different design artifacts. Hera is a model-based design methodology for Web information systems. Adaptation and reuse can be tackled at different design levels in Hera. We illustrate by means of examples how adaptation and reuse can be achieved in the conceptual model, the application model, and the presentation model. Based on a static user profile, adaptation is realized by attaching appearance conditions to model elements. With respect to reusability we do focus on one mechanism that supports it, namely inheritance.

Modeling User Input and Hypermedia Dynamics in Hera

Methodologies for the engineering of Web applications typically provide models that drive the generation of the hypermedia navigation structure in the application. Most of these methodologies and their models consider link following as the only materialization of the navigation structure. In this paper we see how extended user input can dynamically influence the navigation structure. By means of Hera it is shown how one can define this extended user input and capture the functional aspects related to the hypermedia dynamics in the RDF(S)-based design models. For this purpose we discuss the definition of input controls, the representation of state information, and the embedding of both in the application model. We also present the XML/RDF-based architecture implementing this.

Methodologies for Web information system design

The Web information space is rapidly growing in the size and the diversity of both its data and its audience. A consequence is that Web information systems (WIS) in many applications replace existing traditional (not Web based) information systems. Since the nature of WIS differs from the nature of traditional information systems there is a strong demand for design methodologies specifically oriented towards WIS design. The complexity of WIS implies the need for an effective design process and a rigorous and systematic design approach. We argue that besides the quality of the navigation that is typical for Web (hypermedia) data also the adaptation of the presented content is a desired feature of a modern WIS. In this paper we briefly describe the navigation and adaptation design in selected WIS design methodologies, RMM, OOHDM, UWE, and particularly Hera.

A workflow-driven design of web information systems

The World Wide Web is a rapidly growing business environmenthosting a large number of business transactions. Methods fordesigning Web Information Systems (WIS) have adopted processmodels, typically as extensions of the navigation models they arebased on. We observe that the structure of business processes inWIS goes beyond the scope of the navigation structure and deservesto be a more prominent aspect of the design, abstracted from thenavigation specification. This paper explains the design of WISdriven by the specification of business processes of WIS that isused for the automatic generation of models describing theapplication logic including the navigation structure. Thespecification of processes is explained on a conference review andsubmission system and the generation process is demonstrated onthe Hera application model.

Specification of adaptive behavior using a general-purpose design methodology for dynamic web applications

Methodologies for the design and engineering of web applications evolve to accommodate the increased dynamic nature of modern web applications. In this paper we show and demonstrate the similarity between the dynamics in web applications and adaptive hypermedia systems using a general purpose model-driven web design methodology (Hera). To do so we use a simple example. We also stress advantages of specifying adaptivity within models defined on the schema level.

Hypermedia presentation generation in Hera

Hera is a model-driven methodology for designing Semantic Web Information Systems (SWIS). Based on the principle of separation-of-concerns, Hera defines models to describe the different aspects of an SWIS. These models are represented using RDF, the foundation language of the Semantic Web. Hera is composed of two phases: the data collection phase, which integrates data from different sources, and the presentation generation phase, which builds a hypermedia presentation for the integrated data. The focus of this paper is on the hypermedia presentation generation phase and the associated model specifications. The Hera presentation generation phase has two variants: a static one that computes at once a full Web presentation, and a dynamic one that computes one-page-at-a-time by letting the user influence the next Web page to be presented. The dynamic variant proposes, in addition to the models from the static variant, new models to capture the data resulted from the users interaction with the system. The implementation is based on a sequence of data transformations applied to the Hera models that eventually produces a hypermedia presentation.

RDF/XML-based automatic generation of adaptable hypermedia presentations

Hera is a design methodology that supports the development of Web information systems. It is a model-driven method that distinguishes four steps: data retrieval, application model generation, application model instance generation, and presentation data generation. Data retrieval populates the conceptual model with data. In the application model generation the navigational aspects of the application are specified in the application model. Also, the application model needs to be adapted for different user/channel profiles. In the third step of the Hera method, the application model is populated with the retrieved data. The last step considers the physical aspects of the presentation: the retrieved data wrapped in application logic is translated to different implementation platforms (e.g. HTML, WML, SMIL). Having in mind the advantage of Web application interoperability we chose to implement an experimental prototype for the Hera method using RDF(S), the foundation of the semantic Web.