Table-based formal specification approaches for control engineers—empirical studies of usability

The dependability characteristic of the control software of manufacturing systems is highlighted more than before, going through repeated changes to cope with various and varying requirements. Formal methods are researched to be applied to automation system engineering to obtain a more effective and efficient quality assurance. One of the approaches, a formal specification language named Generalised Test Tables has been developed with the aim of intuitiveness and accessibility for automation application developers. The result of the experiments conducted to assess the usability of this language is presented here. Focussing on evaluating effectiveness and user satisfaction, three paper-based experiments have been conducted with students at the bachelor and master level. The evaluation results point to positive usability in both comparative effectiveness to conventional language, that is, Petri Nets, and subjective perception of user satisfaction

An Empirical Study of Control Logic Specifications for Programmable Logic Controllers

This paper presents an empirical study of control logic specifications used to document real-world code in manufacturing applications. More than one hundred input/output related property specifications from ten different reusable function blocks were investigated. The main purpose of the study was to provide understanding of how the specifications are expressed by industrial practitioners. This study can be used to develop new tools and methods for specifying control logic software, as well as evaluating existing ones. In this paper, the studied specifications are used to evaluate linear temporal logic in general and the specification language ST-LTL, tailored for functions blocks, in particular.The study shows that most specifications are expressed as implications between input and output conditions, which should always be fulfilled. Many of these implications are rather complex since the input and output conditions may be mixed and involve sequences, timer issues and non-boolean variables. Using ST-LTL it was possible to represent all implications of this study. The remaining few specifications could be specified in ST-LTL as well after being altered to suit the specification language. The paper demonstrates some advantages of ST-LTL compared to standard linear temporal logic and discusses possible improvements such as support for automatic rewrite of complex specifications

An Empirical Study of Control Logic Specifications for Programmable Logic Controllers

This paper presents an empirical study of control logic specifications used to document real-world code in manufacturing applications. More than one hundred input/output related property specifications from ten different reusable function blocks were investigated. The main purpose of the study was to provide understanding of how the specifications are expressed by industrial practitioners. This study can be used to develop new tools and methods for specifying control logic software, as well as evaluating existing ones. In this paper, the studied specifications are used to evaluate linear temporal logic in general and the specification language ST-LTL, tailored for functions blocks, in particular.The study shows that most specifications are expressed as implications between input and output conditions, which should always be fulfilled. Many of these implications are rather complex since the input and output conditions may be mixed and involve sequences, timer issues and non-boolean variables. Using ST-LTL it was possible to represent all implications of this study. The remaining few specifications could be specified in ST-LTL as well after being altered to suit the specification language. The paper demonstrates some advantages of ST-LTL compared to standard linear temporal logic and discusses possible improvements such as support for automatic rewrite of complex specifications