Lars Pareto

Proving the correctness of reactive systems using sized types

We have designed and implemented a type-based analysis for proving some basic properties of reactive systems. The analysis manipulates rich type expressions that contain information about the sizes of recursively defined data structures. Sized types are useful for detecting deadlocks, nontermination, and other errors in embedded programs. To establish the soundness of the analysis we have developed an appropriate semantic model of sized types.

Recursion and dynamic data-structures in bounded space: towards embedded ML programming

We present a functional language with a type system such that well typed programs run within stated space-bounds. The language is a strict, first-order variant of ML with constructs for explicit storage management. The type system is a variant of Tofte and Talpins region inference system to which the notion of sized types, of Hughes, Pareto and Sabry, has been added.

Architectural descriptions as boundary objects in system and design work

Lean and Agile processes have resolved longstanding problems in engineering communication by replacing document based communication with face-to-face collaboration, but do not yet scale to very large and heterogeneous projects. This paper proposes a compatible extension to lean and agile processes that addresses this limitation. The core idea is to adopt the view of documentation as boundary objects: shared artefacts that maintain integrity across a projects intersecting social worlds. The paper presents a case study, in which interviews with system engineers and designers were analysed to obtain requirements on an architectural description serving as boundary objects in a telecommunications project. The main result is a list of 18 empirically grounded, elementary requirements, worth considering when implementing lean and agile processes in the large.

Communication factors for speed and reuse in large-scale agile software development

An open issue in industry is the combination of software reuse in the context of large scale Agile Software Development. The speed offered by Agile Software Development is needed for short time to market, while reuse strategies such as Software Product Line Engineering are needed for long-term productivity, efficiency, and profit. The paper investigates, through a survey, communication factors affecting both speed and reuse in 3 large companies developing embedded systems and employing Agile Software Development and Software Product Line Engineering. Our results include a prioritized list of communication related factors obtained by statistical analysis and the recognition and spread of the factors in the companies. We have recognized 5 interfaces with the Agile development team that need to be improved: system engineers (architects), product management, distributed teams, inter-project teams and sales unit. Few factors (involving inter-project communication) depend on the business drivers for the company. We also reveal that Agile teams need strategic and architectural inputs in order to be implanted in a large company employing Software Product Line Engineering. Academic and industrial training as well as different tactics for co-location would improve the communication skills of engineers. There is also a need for solutions, in the reference architecture, for fostering Agile Software Development: the goal is the combination of the focus on customer value of the teams, reusability, system requirements and avoidance of organizational dependencies.

Enablers and inhibitors for speed with reuse

An open issue in industry is software reuse in the context of large scale Agile product development. The speed offered by agile practices is needed to hit the market, while reuse is needed for long-term productivity, efficiency, and profit. The paper presents an empirical investigation of factors influencing speed and reuse in three large product developing organizations seeking to implement Agile practices. The paper identifies, through a multiple case study with 3 organizations, 114 business-, process-, organizational-, architecture-, knowledge- and communication factors with positive or negative influences on reuse, speed or both. Contributions are a categorized inventory of influencing factors, a display for organizing factors for the purpose of process improvement work, and a list of key improvement areas to address when implementing reuse in organizations striving to become more Agile. Categories identified include good factors with positive influences on reuse or speed, harmful factors with negative influences, and complex factors involving inverse or ambiguous relationships. Key improvement areas in the studied organizations are intra-organizational communication practices, reuse awareness and practices, architectural integration and variability management. Results are intended to support process improvement work in the direction of Agile product development. Feedback on results from the studied organizations has been that the inventory captures current situations, and is useful for software process improvement work.

Concern coverage in base station development: an empirical investigation

Contemporary model driven development tools only partially support the abstractions occurring in complex embedded systems development. This article presents an interpretive case study in which architectural concerns important to seven engineers in a large product developing organization were compared to the views actually provided by the organization’s models. The paper’s main finding is an empirically grounded catalogue of architectural concerns for a large, complex embedded systems project, and an assessment of the degree to which the studied organization has managed to realize support for these concerns within economical and organizational constraints. In the studied case, 114 different architectural concerns were found to be important to the interviewed engineers. Of this sample, 75% were documented in models, structured text, or informal documentation, whereas 47% of all documented concerns were modeled. The paper’s conclusion is that current modeling languages and methods inadequately address the full set of concerns that are important to engineers in base station development.

Improving Businesses Success by Managing Interactions among Agile Teams in Large Organizations

To achieve successful business, large software companies employ Agile Software Development to be fast and responsive in addressing customer needs. However, a large number of small, independent and fast teams suffer from excessive inter-team interactions, which may lead to paralysis. In this paper we provide a framework to understand how such interactions affect business goals dependent on speed. We detect factors causing observable interaction effects that generate speed waste. By combining data and literature, we provide recommendations to manage such factors, complementing current Agile practices so that they can be adapted in large software organizations.

Role of Architects in Agile Organizations

Agile software development is broadly adopted in industry and works well for small-scale projects. In the context of large-scale development, however, there is a need for additional structure in the form of roles and practices, especially in the area of software architecture. In this chapter, we introduce the CAFFEA framework that defines a model for architecture governance. The framework defines three roles, i.e., chief architect, governance architect, and team architect, as well as a set of practices and responsibilities assigned to these roles. The CAFFEA framework has been developed and validated in close collaboration with several companies.

Concern Visibility in Base Station Development --- An Empirical Investigation

Contemporary model driven development tools only partially support the abstractions occurring in complex embedded systems development. The paper presents an interpretive case study in which the concerns held by 7 engineers in a large product developing organization were compared to the concerns supported by the modeling tool in use. The papers main finding is an empirically grounded catalogue of concerns, categorized with respect to visibility in models and other artefacts in use. In the studied case, 26% of the concerns were visible in the models, whereas 38% were visible elsewhere and 36% not visible at all. The catalogue has been presented to several stakeholders in the unit studied, with positive feedback: particularly appreciated were the notion of concern visibility as indicator of degree of implementation of model driven development, and that concerns have traceable connections to experiences of the units engineers.

Towards Introducing Agile Architecting in Large Companies: The CAFFEA Framework

To continuously deliver value both in short-term and long-term, a key goal for large product lines companies is to combine Agile Software Development with the continuous development and management of software architecture. We have conducted interviews involving several roles at 3 sites from 2 large companies employing Agile. We have identified current architect roles and gaps in the practices employed at the organizations. From such investigation, we have developed an organizational framework, CAFFEA, for Agile architecting, including roles, teams and practices.