In this paper we present SyBeL (System Behaviour modelling Language), an XML based formalism for software system modelling. In particular, SyBeL focuses on the description of the system behaviour in order to capture its functional requirements and has been designed to fulfill some of the most trendy software engineering issues. The use of the underlying XML language makes the artifacts generated by SyBeL immediately available to further automatic manipulation (e. g., to automatically generate test cases) without the need of intermediate models, as usually done in semi-formal approaches. Moreover, we are experimenting SyBeL on a variety of practical case studies.

In this paper we present SMDP (Scenario Model Development Process), an XML-based methodology for the description and manipulation of scenarios that are used to formalize and reuse software requirements. SMDP is an iterative and incremental process that supports scenario evolution during the requirements engineering process. The formalization of scenarios through the underlying XML-based language of SMDP makes them immediately available to further automatic manipulation (e.g., to automatically generate test cases) without the need for intermediate models, as it is usually done in semi-formal approaches. Thanks to the implementation of a software assistant environment for SMDP, the methodology is currently being experimented on a variety of case studies, in particular web applications.

Scenarios are a new way of representing knowledge that has been attracting a lot of attention from practitioners and researchers. In this paper we present the SDML formalism, an XML definition language to support scenario-based requirements engineering. The definition of scenarios through SDML enables to exploit the emerging XML technologies in order to offer powerful ways to create, maintain, distribute and use scenarios. Moreover, we are experimenting the SDML language on a variety of practical case studies.

The Visual Language Compiler-Compiler (VLCC) is a grammar-based graphical system for the automatic generation of visual programming environments. In this paper the theoretical and algorithmic issues of VLCC are discussed in detail. The parsing methodology we present is based on the "positional grammar" model. Positional grammars naturally extend context-free grammars by considering new relations in addition to string concatenation. Thanks to this, most of the results from LR parsing can be extended to the positional grammars inheriting the well known LR technique efficiency. In particular, we provide algorithms to implement a YACC-like tool embedded in the VLCC system for automatic compiler generation of visual languages described by positional grammars.

Refining a specification S1 means to provide another specification S2 which contains all the information given in S1 but with more detail. In this paper, we use logical implication from lower to higher levels of logic specifications to give a definition of refinement between these levels. This guarantees that any property of the higher level is also verified at the lower one. The definition of the relation "is refinement of" is given for specifications which are general first-order theories and it is proved to be transitive. A relevant aspect is that the different levels of logic specifications are in general not immediately comparable, because they can use different vocabularies. For this reason, the concept of transcription is introduced formally in our definition. Then the particular case of Horn specifications is considered. Horn specification semantics can be given by the methodology of least models. This may suggest definitions of the concept of refinement different from the one based on logical implication from lower to higher levels. However, conceptual problems can arise depending on the kind of the refinement definition chosen. Perhaps the most interesting effect is that the property of refinement transitivity may be lost. A possible way to restore the transitivity is provided.