Oddur Benediktsson

COCOMO-Based Effort Estimation for Iterative and Incremental Software Development

Incremental software development and delivery have been used in software projects in many ways for many years. Justifications for incremental approaches include risk amelioration, the management of evolving requirements, and end-user involvement. Incremental development, including iterative, incremental delivery, has become a norm in many sectors. However, there has been little work on modelling the effort in such development and hence a dearth of comparative analyses of cost models for incremental development/delivery. We attempt to rectify this by proposing a COCOMO-style effort model for incremental development/delivery and explore the relationship between effort and the number of increments, thereby providing new insights into the economic impact of incremental approaches to software projects.

Comparison of software development life cycles: a multiproject experiment

A variety of life cycle models for software development are generally available. Many of the variations were composed to overcome problems in the classic waterfall model. However, it is generally difficult to compare and contrast the methods and very little literature is available to guide developers and managers in making choices. Moreover, in order to make informed decisions, developers require access to real data that compares the different models and the results associated with the adoption of each model. An experiment in which 15 software teams developed comparable software products, using four different development approaches (V-model, incremental model, evolutionary model, and extreme programming), is described. Extensive measurements were taken to assess the time, quality, size, and development efficiency of each product. The experimental data collected and the conclusions related to the choice of method, its impact on the project and the quality of the results, are presented.

Effort Estimation in Incremental Software Development

Incremental software development offers many benefits compared with more traditional development approaches. Indeed, incremental approaches have been utilised for many years due to the involvement of users, the early demonstration of capability and the potential for risk reduction that they offer. However, there appears to have been little work on modelling, planning and controlling incremental development. The paper attempts to introduce a quantitative analytical framework for evaluating such approaches and their impacts on the development effort. Models that predict development effort as an exponential function of product size are used in the paper to explore some of the relationships between effort and the number of increments, thereby providing new insights into the economic impact of incremental approaches to software projects.

Development life cycle management: a multiproject experiment

A variety of life cycle models for software systems development are generally available. However, it is generally difficult to compare and contrast the methods and very little literature is available to guide developers and managers in making choices. Moreover in order to make informed decisions developers require access to real data that compares the different models and the results associated with the adoption of each model. This paper describes an experiment in which fifteen software teams developed comparable software products using four different development approaches (V-model, incremental, evolutionary and extreme programming). Extensive measurements were taken to assess the time, quality, size, and development efficiency of each product. The paper presents the experimental data collected and the conclusions related to the choice of method, its impact on the project and the quality of the results as well as the general implications to the practice of systems engineering project management.

Processes for Software in Safety Critical Systems

Two complementary standards are compared, both of which are concerned with the production of quality software. One, IEC 61508, is concerned with the safety of software intensive systems and the other, ISO/IEC TR 15504, takes a process view of software capability assessment. The standards are independent, though both standards build on ISO/IEC 12207. The paper proposes a correspondence between the safety integrity levels (SILs) of 61508 and the capability levels (CLs) of 15504, and considers the appropriateness of the 15504 reference model as a framework for assessing safety critical software processes. Empirical work from the SPICE trials and COCOMO II is used to support the arguments of the paper as well as to investigate their consequences. The development of a 15504 compatible assessment model for software in safety critical systems is proposed.

An Incremental Approach to Software Process Assessment and Improvement

Abstract This paper considers assessment techniques based on the use of questionnaires, assessment matrices, workshops, and pro-forma assessment schemas; together with people issues such as motivation and involvement. With strong reference to SPICE process capability levels and the European Foundation for Quality Management (EFQM) Excellence Model, the authors suggest a novel framework containing a possible sequence of improvement steps towards the Established Level 3. The main conclusion in this paper is that an incremental improvement path can be defined using process assessment that commences with questionnaires, then goes on to matrices, workshops, and finally reaches pro-formas. Furthermore, it seems quite plausible that all four types of assessment techniques should be employed on an ongoing basis in a staged fashion.

Estimating size in incremental software development projects

The motivation for this work is derived from the current interest in speeding up development schedules. A key implication of the shift to more rapid development methods is the growing emphasis on fixed time and fixed effort delivered during such projects. However, there appears to be little work that addresses the impacts of dealing with bound effort levels. The result of binding time and effort is to deprive project managers of the normal parameters that are used in trade-offs. The paper attempts to introduce a quantitative analytical framework for modelling effort-boxed development in order to uncover the effects on the overall development effort and the potential leverage that can be derived from incremental delivery in such projects. Models that predict product size as an exponential function of the development effort are used in the paper to explore the relationships between effort and the number of increments, thereby providing new insights into the economic impact of incremental approaches to effort-boxed software projects.

New Insights into Effort Estimation for Incremental Software Development Projects

Incremental software development, the staged delivery of products, offers many benefits compared with more traditional development approaches. Indeed, incremental approaches have been utilized for many years due to the involvement of users, early demonstration of capability, and potential for risk reduction that they offer. However, there appears to have been little work on modeling, planning and controlling incremental development. This paper attempts to introduce a quantitative analytical framework for evaluating such approaches and their economic impacts. The use of a Constructive Cost Model (COCOMO)-style effort framework developed in this paper explores some of the relationships between effort and the number of increments, thereby providing new insights into the economic impact of incremental approaches to software projects.

Managing Software Development Project Size : Overcoming the Effort-Boxing Constraint

The motivation for this work is derived from the current interest in speeding up development schedules for information technology(IT) projects. A keyimplication of the shift to more rapid development methods is the growing emphasis on fixed time and fixed effort delivered during such projects. However, there appears to be little work that addresses the impacts of dealing with bound effort levels. The result of binding time and effort is to deprive project managers of the normal parameters that are used in trade-offs. The paper introduces a quantitative analytical framework for modeling effort-boxed development in order to uncover the effects on the overall development effort and the potential leverage that can be derived from incremental delivery in such projects. Models that predict product size as an exponential function of the development effort are used in the paper to explore the relationships between effort and the number of increments, thereby providing new insights into the economic impact of incremental approaches to effort-boxed software projects.

WORKING WITH ALTERNATIVE DEVELOPMENT LIFE CYCLES: A MULTIPROJECT EXPERIMENT

1. MOTIVATION Should the Waterfall model be dropped in favour of more modern approaches such as incremental development and eXtreme Programming? Many developers appear to show a preference for such modern approaches but there appears to be very little non-anecdotal data that substantiates such choices. IS, software development and software engineering books discuss the alternatives but offer little in the way of direct comparison and explicit metrics that address the impacts on the product, project and people. The classic Waterfall model was refined in the early 1970s to cope with the larger and more demanding software projects characterised by a growing level of complexity. It was heavily influenced by early attempts to introduce structure into the programming process