Gunter Mussbacher

A Lightweight GRL Profile for i* Modeling

The i* framework is a popular conceptual modeling language for capturing and analyzing socio-technical motivation and properties of complex systems in terms of actors, their intentions, and their relationships. In November 2008, the International Telecommunications Union finalized the standardization of the User Requirements Notation (URN). URN is composed of two loosely coupled yet integrated sub-languages: the Goal-oriented Requirement Language (GRL), which is an intentional modeling language based on a subset of i*, and the Use Case Map notation for representing and capturing high-level system scenarios and structures. GRL was specifically defined in a non-restrictive way to foster the development and use of different agent and/or goal modeling approaches and techniques. However, because of its permissiveness, GRL can be used in ways that deviate from conventional i* modeling guidelines. In addition, some i* concepts do not have equivalent first-class concepts in GRL. In this paper, we present a lightweight GRL profile for i* that takes advantage of GRLs extensibility features to capture missing i* concepts. The profile presents formal constraints on the use of GRL and its extensions to restrict it to an i* style. Using GRL constrained by this profile enables GRL modeling and analysis tools to be used for i* models, and ensures that resulting i* models conform to an international standard and that they can be integrated with Use Case Maps. Variants and extensions of the original i* can also be supported in a similar way. This profile is implemented in the jUCMNav modeling tool.

Towards advanced goal model analysis with jUCMNav

Goal modeling is an important part of various types of activities such as requirements engineering, business management, and compliance assessment. The Goal-oriented Requirement Language is a standard and mature goal modeling language supported by the jUCMNav tool. However, recent applications of GRL to a regulatory context highlighted several analysis issues and limitations whose resolutions are urgent, and also likely applicable to other languages and tools. This paper investigates issues related to the computation of strategy and model differences, the management of complexity and uncertainty, sensitivity analysis, and various domain-specific considerations. For each, a solution is proposed, implemented in jUCMNav, and illustrated through simple examples. These solutions greatly increase the analysis capabilities of GRL and jUCMNav in order to handle real problems.

Concern-Oriented Software Design

There exist many solutions to solve a given design problem, and it is difficult to capture the essence of a solution and make it reusable for future designs. Furthermore, many variations of a given solution may exist, and choosing the best alternative depends on application-specific high-level goals and non-functional requirements. This paper proposes Concern-Oriented Software Design, a modelling technique that focuses on concerns as units of reuse. A concern groups related models serving the same purpose, and provides three interfaces to facilitate reuse. The variation interface presents the design alternatives and their impact on non-functional requirements. The customization interface of the selected alternative details how to adapt the generic solution to a specific context. Finally, the usage interface specifies the provided behaviour. We illustrate our approach by presenting the concern models of variations of the Observer design pattern, which internally depends on the Association concern to link observers and subjects.

URN: towards a new standard for the visual description of requirements

In November 1999, the International Telecommunication Union (ITU-T, SG 17) initiated a question on the standardization of a User Requirements Notation (URN) for complex reactive, distributed, and dynamic systems and applications. URN is intended to be standardized by September 2003. This paper presents the motivations behind URN, its objectives, and the current proposal that combines two complementary languages. The first one, GRL (Goal-oriented Requirement Language), is used to describe business goals, nonfunctional requirements, alternatives, and rationales. The second one, UCM (Use Case Maps), enables the description of functional requirements as causal scenarios. The introduction of URN is likely to impact the development ans use of other SG 17 languages (especially MSC and SDL) as well as OMGs UML. This paper briefly explores several relations between these languages as well as potential for synergy and coordination.

Visualizing early aspects with use case maps

Once aspects have been identified during requirements engineering activities, the behavior, structure, and pointcut expressions of aspects need to be modeled unobtrusively at the requirements level, allowing the engineer to seamlessly focus either on the behavior and structure of the system without aspects or the combined behavior and structure. Furthermore, the modeling techniques for aspects should be the same as for the base system, ensuring that the engineer continues to work with familiar models. This paper describes how, with the help of Use Case Maps (UCMs), scenario-based aspects can be modeled at the requirements level unobtrusively and with the same techniques as for non-aspectual systems. Use Case Maps are a visual scenario notation under standardization by the International Telecommunication Union. With Use Case Maps, aspects as well as pointcut expressions are modeled in a visual way which is generally considered the preferred choice for models of a high level of abstraction.

The relevance of model-driven engineering thirty years from now

Although model-driven engineering (MDE) is now an established approach for developing complex software systems, it has not been universally adopted by the software industry. In order to better understand the reasons for this, as well as to identify future opportunities for MDE, we carried out a week-long design thinking experiment with 15 MDE experts. Participants were facilitated to identify the biggest problems with current MDE technologies, to identify grand challenges for society in the near future, and to identify ways that MDE could help to address these challenges. The outcome is a reflection of the current strengths of MDE, an outlook of the most pressing challenges for society at large over the next three decades, and an analysis of key future MDE research opportunities.

Requirements modeling with the aspect-oriented user requirements notation (AoURN): a case study

The User Requirements Notation (URN) is a recent ITU-T standard that supports requirements engineering activities. The Aspect-oriented URN (AoURN) adds aspect-oriented concepts to URN, creating a unified framework that allows for scenario-based, goal-oriented, and aspect-oriented modeling. AoURN is applied to the car crash crisis management system (CCCMS), modeling its functional and non-functional requirements (NFRs). AoURN generally models all use cases, NFRs, and stakeholders as individual concerns and provides general guidelines for concern identification. AoURN handles interactions between concerns, capturing their dependencies and conflicts as well as the resolutions. We present a qualitative comparison of aspect-oriented techniques for scenario-based and goal-oriented requirements engineering. An evaluation carried out based on the metrics adapted from literature and a task-based evaluation suggest that AoURN models are more scalable than URN models and exhibit better modularity, reusability, and maintainability.

AoURN-based modeling and analysis of software product lines

Software Product Line Engineering concerns itself with domain engineering and application engineering. During domain engineering, the whole product family is modeled with a preferred flavor of feature models and additional models as required (e.g., domain models or scenario-based models). During application engineering, the focus shifts toward a single family member and the configuration of the member’s features. Recently, aspectual concepts have been employed to better encapsulate individual features of a Software Product Line (SPL), but the existing body of SPL work does not include a unified reasoning framework that integrates aspect-oriented feature description artifacts with the capability to reason about stakeholders’ goals while taking feature interactions into consideration. Goal-oriented SPL approaches have been proposed, but do not provide analysis capabilities that help modelers meet the needs of the numerous stakeholders involved in an SPL while at the same time considering feature interactions. We present an aspect-oriented SPL approach for the requirements phase that allows modelers (a) to capture features, goals, and scenarios in a unified framework and (b) to reason about stakeholders’ needs and perform trade-off analyses while considering undesirable interactions that are not obvious from the feature model. The approach is based on the Aspect-oriented User Requirements Notation (AoURN) and helps identify, prioritize, and choose products based on analysis results provided by AoURN editor and analysis tools. We apply the AoURN-based SPL framework to the Via Verde SPL to demonstrate the feasibility of this approach through the selection of a Via Verde product configuration that satisfies stakeholders’ needs and results in a high-level, scenario-based specification that is free from undesirable feature interactions.

Goal and scenario modeling, analysis, and transformation with jUCMNav

jUCMNav is an open-source Eclipse plug-in that supports the definition, analysis, transformation, and management of requirements engineering models expressed with the User Requirements Notation (URN). In November 2008, URN was approved as a standard by the International Telecommunication Union (ITU-T). URN is the first standard that combines modeling concepts and notations for goals and intentions (mainly for non-functional requirements, quality attributes, and reasoning about alternatives) and scenarios (mainly for operational requirements, functional requirements, and reasoning about scenario interactions, performance, and high-level architecture). jUCMNav has been instrumental in validating key concepts for the current standard as well as prototyping new concepts.

Visualizing Aspect-Oriented Goal Models with AoGRL

As goal models can be large and complex even for small problems, it is often a challenge to aptly visualize them and to efficiently structure them for maintenance and reuse activities. The Goal-oriented Requirement Language (GRL) based on i* and the Non- Functional Requirements (NFR) Framework is no exception regarding these challenges. We argue that new ways of visualizing GRL goal models are needed and propose to use Aspect-oriented GRL (AoGRL) to improve the current structure of GRL models and their visualization. The paper presents a case study to evaluate the modularity, understandability, reusability, maintainability, and scalability of AoGRL models compared to GRL models. The evaluation is carried out based on metrics adapted from literature. The evaluation suggests that AoGRL models are more scalable than GRL models and exhibit better modularity, under standability, reusability, and maintainability.