Sascha Konrad

Real-time specification patterns

Embedded systems are pervasive and frequently used for critical systems with time-dependent functionality. Dwyer et al. (1999) have developed qualitative specification patterns to facilitate the specification of critical properties, such as those that must be satisfied by embedded systems. Thus far, no analogous repository has been compiled for realtime specification patterns. This paper makes two main contributions: First, based on an analysis of timing-based requirements of several industrial embedded system applications, we created real-time specification patterns in terms of three commonly used real-time temporal logics. Second, as a means to further facilitate the understanding of the meaning of a specification, we offer a structured English grammar that includes support for real-time properties. We illustrate the use of the real-time specification patterns in the context of property specifications of a real-world automotive embedded system.

Requirements patterns for embedded systems

In software engineering, design patterns propose solution skeletons for common design problems. The solution skeleton is described in such a way that the design can be used for other projects, where each application tailors the design to specific project constraints. This paper describes research into investigating how a similar approach to reuse can be applied to requirements specifications, which we term requirements patterns. Specifically, the paper explores how object-oriented modeling notations, such as the Unified Modeling Language (UML), can be used to represent common requirements patterns. Structural and behavioral information are captured as part of a requirements pattern. In order to maximise reuse, we focus on requirements patterns for embedded systems. This paper also describes case studies that illustrate how we have applied these general patterns to multiple embedded systems applications from the automotive industry.

Facilitating the construction of specification pattern-based properties

Formal specification languages are often perceived as difficult to use by practitioners, and are therefore rarely-used in industrial software development practices. Numerous researchers have developed specification pattern systems to facilitate the construction of formal specifications of system properties. Feedback indicates that these patterns are considered helpful, but many practitioners prefer capturing properties using informal notations, such as natural language, instead of formal specification languages. This paper describes a project that addresses this technology gap. First, we introduce a stepwise process for deriving and instantiating system properties in terms of their natural language representations. The key components of this process are structured natural language grammars and specification pattern systems. Second, we describe SPIDER, a prototype implementation of a tool suite supporting this specification process. We illustrate the use of our approach with a description of a stepwise construction process of property specifications of a real-world automotive embedded system using Spider.

Object analysis patterns for embedded systems

Some of the most challenging tasks in building a software system are capturing, refining, and analyzing requirements. How well these tasks are performed significantly impacts the quality of the developed software system. The difficulty of these tasks is greatly exacerbated for the software of embedded systems as these systems are commonly used for critical applications, have to operate reliably for long periods of time, and usually have a high degree of complexity. Current embedded systems software development practice, however, often deals with the (requirements) analysis phase in a superficial manner, instead emphasizing design and implementation. This research investigates how an approach similar to the well-known design patterns, termed object analysis patterns, can be applied in the analysis phase of embedded systems development, prior to design and coding. Specifically, our research explores how object-oriented modeling notations, such as the Unified Modeling Language (UML), can be used to represent structural and behavioral information as part of commonly occurring object analysis patterns. This work also investigates how UML-based conceptual models of embedded systems, based on the diagram templates in the object analysis patterns, can be automatically analyzed using the Spin model checker for adherence to properties specified in linear-time temporal logic (LTL) using a previously developed UML formalization framework. We have applied these patterns to several embedded systems applications obtained from the automotive industry. This paper describes one of our case studies and illustrates how our approach facilitates the construction of UML-based conceptual models of embedded systems and the analysis of these models for adherence to functional requirements.

Requirements Engineering in the Development of Large-Scale Systems

Requirements engineering is arguably the most important activity in the development of complex, software-intensive systems. Generally, the higher the complexity of the system under development, the more exacerbated the importance of good requirements engineering becomes. While numerous researchers in academia have focused on requirements engineering, there is still a need for practical guidelines that scale to real-world applications. This paper presents requirements engineering challenges faced and lessons learned addressing these challenges in a large-scale industrial project. The implementation of these lessons greatly contributed to the success of the project.

Visualizing Requirements in UML Models

As the Unified Modeling Language (UML) and modeldriven development (MDD) become increasingly common in industry, many developers are faced with the difficult task of understanding how an existing UML model realizes system requirements. Essentially, developers are required to understand the structure and behavior of UML models that they may have not created. Understanding these relationships is non-trivial, because the interactions in the model are not readily apparent. Commonly, the only means to elicit these relationships is visual inspection and guided simulation. This paper describes an alternative approach termed REVU (Requirements Visualization of UML), a process for visualizing functional requirements in terms of behavioral interactions in a UML model. We illustrate the use of this process with the visualization of scenarios for an adaptive light control system.

Automated analysis of natural language properties for UML models

It is well known that errors introduced early in the development process are commonly the most expensive to correct. The increasingly popular model-driven architecture (MDA) exacerbates this problem by propagating these errors automatically to design and code. This paper describes a round trip engineering process that supports the specification of a UML model using CASE tools, the analysis of specified natural language properties, and the subsequent model refinement to eliminate errors uncovered during the analysis. This process has been implemented in Spider, a tool suite that enables developers to specify and analyze a UML model with respect to behavioral properties specified in terms of natural language.

Automated analysis of timing information in UML diagrams

This work introduces an approach to adding timing information to UML diagrams for modeling embedded systems. In order to perform automated formal analysis of these UML diagrams with timing information, we extend a previously developed UML formalization framework to provide Promela semantics for the timing elements of the UML diagrams. The paper describes the application of our approach to an electronically controlled steering system obtained from one of our industrial collaborators.

A requirements patterns-driven approach to specify systems and check properties

We previously developed a framework, Hydra, for adding formal semantics to a collection of UML diagrams that enable the automated derivation of formal language specifications for those diagrams. Recently, we have also identified a number of requirements patterns for embedded systems that includes sample UML structural and behavioral diagrams for modeling requirements and high-level design for embedded systems. This paper describes a requirements patterns-driven approach for developing UML diagrams for embedded systems, where each pattern has a constraints section to specify safety and other invariant properties. We show how the diagrams for an industrial automotive system, via specifications generated from Hydra, can be automatically analyzed for adherence to these formally specified constraints using the SPIN model checker. We developed the MINERVA framework to support the graphical construction of UML diagrams and to visualize the results from the SPIN analysis in terms of the original UML diagrams.

Formal definition of syntax and semantics for documenting variability in activity diagrams

Quality assurance is an important issue in product line engineering. It is commonly agreed that quality assurance in domain engineering requires special attention, since a defect in a domain artifact can affect several products of a product line and can lead to high costs for defect correction. However, the variability in domain artifacts is a special challenge for quality assurance, since quality assurance approaches from single system engineering cannot handle the variability in domain artifacts. Therefore, the adaptation of existing approaches or the development of new approaches is necessary to support quality assurance in domain engineering. Activity diagrams are a widely accepted modeling language used to support quality assurance activities in single system engineering. However, current quality assurance approaches adapted for product line engineering using activity diagrams are not based on a formal syntax and semantics and therefore techniques based on these approaches are only automatable to a limited extent. In this paper, we propose a formal syntax and semantics for documenting variability in activity diagrams based on Petri-nets which provide the foundation for an automated support of quality assurance in domain engineering.