Rami Marelly

Specifying and executing behavioral requirements: the play-in/play-out approach

A powerful methodology for scenario-based specification of reactive systems is described, in which the behavior is “played in” directly from the system’s GUI or some abstract version thereof, and can then be “played out”. The approach is supported and illustrated by a tool, which we call the play-engine. As the behavior is played in, the play-engine automatically generates a formal version in an extended version of the language of live sequence charts (LSCs). As they are played out, it causes the application to react according to the universal (“must”) parts of the specification; the existential (“may”) parts can be monitored to check their successful completion. Play-in is a user-friendly high-level way of specifying behavior and play-out is a rather surprising way of working with a fully operational system directly from its inter-object requirements. The ideas appear to be relevant to many stages of system development, including requirements engineering, specification, testing, analysis and implementation.

Formal Modeling of C. elegans Development: A Scenario-Based Approach

We present preliminary results of a new approach to the formal modeling of biological phenomena. The approach stems from the conceptual compatibility of the methods and logic of data collection and analysis in the field of developmental genetics with the languages, methods and tools of scenario-based reactive system design. In particular, we use the recently developed methodology consisting of the language of live sequence charts with the play-in/play-out process, to model the well-characterized process of cell fate acquisition during C. elegans vulval development.

Playing with time: on the specification and execution of time-enriched LSCs

We extend live sequence charts (LSCs), a highly expressive variant of sequence diagrams, with timing constructs, thus making the language suitable for specifying the behavioral requirements of time-intensive systems. We follow R. Alur and T.A. Henzinger (see Software Tools for Technology Transfer, vol.1, p.86-109, 1997) in basing the extension on a single clock object. We have implemented the extension in full in our play-engine tool, which provides user-friendly ways to play in the timing constraints, together with a powerful mechanism that can execute, or play out, the time-enriched requirements directly, without the need for an intra-object system model. It seems that in addition to many advantages in testing and requirements engineering, for some kinds of systems this could lead to the requirements actually serving as the final implementation.

Multiple instances and symbolic variables in executable sequence charts

We extend live sequence charts (LSCs), a highly expressive variant of sequence diagrams, and provide the extension with an executable semantics. The extension involves support for instances that can bind to multiple objects and symbolic variables that can bind to arbitrary values. The result is a powerful executable language for expressing behavioral requirements on the level of inter-object interaction. The extension is implemented in full in our play-engine tool, with which one can execute the requirements directly without the need to build or synthesize an intra-object system model. It seems that in addition to many advantages in testing and requirements engineering, for some kinds of systems this could lead to the requirements actually serving as the final implementation.

An initial wise development environment for behavioral models

We present a development environment that proactively and interactively assists the software engineer in modeling complex reactive systems. Our framework repeatedly analyzes models of the system under development at various levels of abstraction, and then reasons about these models in order to detect possible errors and to derive emergent properties of interest. Upon request, the environment can then augment the system model in order to repair or avoid detected behavior that is undesired, or instrument it in order to monitor the execution for certain behaviors. Specialized automated and human-assisted techniques are incorporated to direct and prioritize the analysis and related tasks, based on the relevance of the observed properties and the expected impact of actions to be taken. Our development environment is an initial step in the direction of the very recent Wise Computing vision, which calls for turning the computer (namely, the development environment) into an equal member of the development team: knowledgeable, independent, concerned and proactively involved in the development process. Our tool is implemented within the context of behavioral programming (BP), a scenario-based modeling approach, where components are aligned with how humans often describe desired system behavior. Thus, our work further enhances the naturalness and incrementality of developing in BP.

Wise Computing: Toward Endowing System Development with Proactive Wisdom

A broad, long-term research project is described, which will lead to the computer becoming an equal member of the system-development team, continuously making proactive contributions, akin to those expected from an experienced and knowledgeable customer or user, a conscientious QA engineer, a strict regulatory auditor, an engineering -team leader, or the organization’s CTO. The web extra at https://youtu.be/mmrv8ZACbpU describes the authors’ novel “wise computing” approach and demonstrates one possible application. The second web extra at https://youtu.be/DtpvMxMwYPM extends the discussion of the authors’ novel “wise computing” approach and presents a case study.

Scenario-based programming for mobile applications

We introduce a novel method for creating mobile applica-tions, integrating the Android SDK into PlayGo, a scenario-based behavioral programming framework. The method al-lows creating mobile applications simply by using a visualGUI editor, and then incrementally “playing in” scenariosthat construct the application’s behavior. This allows thedeveloper to focus on the behavior and interface rather thanon the syntax and code.

Assignments and Implemented Functions

We often want to use data manipulation algorithms and functions that are applied to specified variables. These algorithms and functions usually cannot (and should not) be described using LSC-style interactions between objects but are better viewed as external pieces of computation or logic to be worked into the scenarios. In this chapter we discuss these, and the assignment statements that can be used to apply them.

Testing with Existential Charts

Universal charts, which must be satisfied by any run that satisfies their prechart, ‘drive’ the model by their action/reaction nature. In contrast, existential charts, which can get by with only a single satisfying run, can be used as system tests or as examples of object interactions. In this chapter, we deal with the uses of existential charts and the way they are monitored by the Play-Engine.

A Play-Engine Aware GUI Editor

This chapter describes GUIEdit, a rather rudimentary editor we have built to help the user construct GUI applications that can be used with the Play-Engine.