Øystein Haugen

STAIRS towards formal design with sequence diagrams

The paper presents STAIRS [1], an approach to the compositional development of UML interactions supporting the specification of mandatory as well as potential behavior. STAIRS has been designed to facilitate the use of interactions for requirement capture as well as test specification. STAIRS assigns a precise interpretation to the various steps in incremental system development based on an approach to refinement known from the field of formal methods and provides thereby a foundation for compositional analysis. An interaction may characterize three main kinds of traces. A trace may be (1) positive in the sense that it is valid, legal or desirable, (2) negative meaning that it is invalid, illegal or undesirable, or (3) inconclusive meaning that it is considered irrelevant for the interaction in question. The basic increments in system development proposed by STAIRS, are structured into three main kinds referred to as supplementing, narrowing and detailing. Supplementing categorizes inconclusive traces as either positive or negative. Narrowing reduces the set of positive traces to capture new design decisions or to match the problem more adequately. Detailing involves introducing a more detailed description without significantly altering the externally observable behavior.

An algorithm for generating t-wise covering arrays from large feature models

A scalable approach for software product line testing is required due to the size and complexity of industrial product lines. In this paper, we present a specialized algorithm (called ICPL) for generating covering arrays from feature models. ICPL makes it possible to apply combinatorial interaction testing to software product lines of the size and complexity found in industry. For example, ICPL allows pair-wise testing to be readily applied to projects of about 7,000 features and 200,000 constraints, the Linux Kernel, one of the largest product lines where the feature model is available. ICPL is compared to three of the leading algorithms for t-wise covering array generation. Based on a corpus of 19 feature models, data was collected for each algorithm and feature model when the algorithm could finish 100 runs within three days. These data are used for comparing the four algorithms. In addition to supporting large feature models, ICPL is quick, produces small covering arrays and, even though it is non-deterministic, produces a covering array of a similar size within approximately the same time each time it is run with the same feature model.

Properties of realistic feature models make combinatorial testing of product lines feasible

Feature models and associated feature diagrams allow modeling and visualizing the constraints leading to the valid products of a product line. In terms of their expressiveness, feature diagrams are equivalent to propositional formulas which makes them theoretically expensive to process and analyze. For example, satisfying propositional formulas, which translates into finding a valid product for a given feature model, is an NP-hard problem, which has no fast, optimal solution. This theoretical complexity could prevent the use of powerful analysis techniques to assist in the development and testing of product lines. However, we have found that satisfying realistic feature models is quick. Thus, we show that combinatorial interaction testing of product lines is feasible in practice. Based on this, we investigate covering array generation time and results for realistic feature models and find where the algorithms can be improved.

Modeling and analysis of real-time and embedded systems

This paper presents an overview of the workshop MARTES on Modeling and Analysis of Real-time and Embedded Systems that has taken place for the first time in association with the MODELS/UML 2005 conference. The main themes discussed at this workshop concerned (1) methodologies and tools for quantitative analysis and (2) methodologies and languages for modeling quantitative aspects of real-time and embedded systems in the context of model driven development.

Consolidated Product Line Variability Modeling

In this chapter we present an improved and simplified metamodel for product line variability. This model has been consolidated from diverse approaches in the earlier research projects ESAPS, CAF and other existing work, supplied with recent research in FAMILIES. The consolidated metamodel aims to be the starting point for standardization. A standard will lay the grounds for commercial and open-source tool support. We present here a prototype tool based on the metamodel. To put the work in context, we present three different approaches for capturing variability: using standard languages (exemplified by UML 2.0), using annotations to standard languages, and using domain-specific languages. We use the same Watch example to present how variability is handled in all three approaches.

STAIRS - Steps to Analyze Interactions with Refinement Semantics

The paper presents STAIRS, an approach to the compositional development of UML interactions supporting the specification of mandatory as well as potential behavior. STAIRS has been designed to facilitate the use of interactions for requirement capture as well as test specification. STAIRS assigns a precise interpretation to the various steps in incremental system development based on an approach to refinement known from the field of formal methods, and provides thereby a foundation for compositional analysis. An interaction may characterize three main kinds of traces. A trace may be (1) positive in the sense that it is valid, legal or desirable, (2) negative meaning that it is invalid, illegal or undesirable, or (3) considered irrelevant for the interaction in question. This categorization corresponds well with that of testing where the verdict of a test execution is either pass, fail or inconclusive. The basic increments in system development are structured into three kinds referred to as supplementing, narrowing and detailing. Supplementing categorizes inconclusive traces as either positive or negative. Narrowing reduces the set of positive traces to capture new design decisions or to match the problem more adequately. Detailing involves introducing a more detailed description without significantly altering the externally observable behavior.

CVL: common variability language

The tutorial will present the present the outcome of the work done by the Joint Submission Team against the Request For Proposals for a Common Variability Language issued by the OMG (Object Management Group). The tutorial will present the language and experiments done by some of the consortium members on tools supporting preliminary tools for CVL.

Why timed sequence diagrams require three-event semantics

STAIRS is an approach to the compositional development of sequence diagrams supporting the specification of mandatory as well as potential behavior. In order to express the necessary distinction between black-box and glass-box refinement, an extension of the semantic framework with three event messages is introduced. A concrete syntax is also proposed. The proposed extension is especially useful when describing time constraints. The resulting approach, referred to as Timed STAIRS, is formally underpinned by denotational trace semantics. A trace is a sequence of three kinds of events: events for transmission, reception and consumption. We argue that such traces give the necessary expressiveness to capture the standard UML interpretation of sequence diagrams as well as the black-box interpretation found in classical formal methods.

Generating better partial covering arrays by modeling weights on sub-product lines

Combinatorial interaction testing is an approach for testing product lines. A set of products to test can be set up from the covering array generated from a feature model. The products occurring in a partial covering array, however, may not focus on the important feature interactions nor resemble any actual product in the market. Knowledge about which interactions are prevalent in the market can be modeled by assigning weights to sub-product lines. Such models enable a covering array generator to select important interactions to cover first for a partial covering array, enable it to construct products resembling those in the market and enable it to suggest simple changes to an existing set of products to test for incremental adaption to market changes. We report experiences from the application of weighted combinatorial interaction testing for test product selection on an industrial product line, TOMRAs Reverse Vending Machines.

The Future of Train Signaling

Producing the source code for a railway interlocking system based on the description of a station has traditionally been a multistage manual process. We show how this process can be automated and made less error-prone by introducing model-driven development (MDD). This paper addresses the experience of developing a Domain Specific Language (DSL) to describe railway stations, Train Control Language (TCL), and tools to support this language. In the railroad domain where there are extreme safety requirements, it is essential to show that consistency and completeness can be assured. We address how the model is used to generate several different representations for different purposes. We look at advantages and challenges with our approach, and we discuss improvements to existing technologies to support our case better.