A graphical tabular model for rule-based logic programming and verification

New trends in development of databases and expert systems seems to underline the role of graphical specification tools, visual information modeling and formal verification procedures. This paper incorporates these new ideas and, moreover, tries to present putting them in engineering practice. The main goal is to move the design procedure to a more abstract, logical level, where knowledge specification is based on use of abstract rule representation, called eXtended Tabular Trees. The main idea behind XTT is to build a hierarchy of ObjectAttribute-Value Tables (OAV table). The basic component for knowledge specification is an OAV table. It is analogous to a relational database table; however, it contains conditional part and decision columns. Moreover, the attribute values can be non-atomic ones. Each row provides specification of a single rule. The OAV tables can be connected with one another through appropriate links specifying the control flow in the system. The design specification is automatically translated into Prolog code, so the designer can focus on logical specification of safety and reliability. On the other hand, formal aspects such as completeness, determinism, etc. are automatically verified on-line during the design, so that it verifiable characteristics are preserved. From practical point of view, the design process is performed with a intelligent tool named Mirella.