Effort Estimation of Use Cases for Incremental large scale softwares

Effort Estimation of Use Cases for Incremental large scale softwares

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Effort Estimation of Use Cases for Incremental Large-Scale Software Development Parastoo Mohagheghi Department of Computer and Information Science Norwegian University of Science and Technology NO-7491 Trondheim, Norway and Faculty of Engineering Agder University College NO-4876 Grimstad, Norway +47 37 25 34 22 parastoo@idi.ntnu.no Bente Anda Simula Research Laboratory P.O.Box 134 NO-1325 Lysaker, Norway +47 67 82 83 06 bentea@simula.no Reidar Conradi Department of Computer and Information Science Norwegian University of Science and Technology NO-7491 Trondheim, Norway and Simula Research Laboratory P.O.Box 134 NO-1325 Lysaker, Norway +47 73 59 34 44 conradi@idi.ntnu.no ABSTRACT This paper describes an industrial study of an effort estimation method based on use cases, the Use Case Points method. The original method was adapted to incremental development and evaluated on a large industrial system with modification of software from the previous release. We modified the following elements of the original method: a) complexity assessment of actors and use cases, and b) the handling of non-functional requirements and team factors that may affect effort. For incremental development, we added two elements to the method: c) counting both all and the modified actors and transactions of use cases, and d) effort estimation for secondary changes of software not reflected in use cases. We finally extended the method to: e) cover all development effort in a very large project. The method was calibrated using data from one release and it produced an estimate for the successive release that was only 17% lower than the actual effort. The study identified factors affecting effort on large projects with incremental development. It also showed how these factors can be calibrated for a specific context and produce relatively accurate estimates. Categories and Subject Descriptors D.2.9 [ Software Engineering ]: Management – cost estimation, life cycle. General Terms Management, Experimentation. Keywords Estimation, use cases, incremental development. 1. INTRODUCTION Effort estimation is a challenge in every software project. The estimates will impact costs and expectations on schedule, functionality and quality. While expert estimates are widely used, they are difficult to analyze and the estimation quality depends on the experience of experts from similar projects. Alternatively, more formal estimation models can be used. Traditionally, software size estimated in the number of Source Lines of Code (SLOC), Function Points (FP) and Object Points (OP) are used as input to these models, e.g. COCOMO and COCOMO II [5]. Because of difficulties in estimating SLOC, FP or OP, and because modern systems are often developed using the Unified Modeling Language (UML), UML-based software sizing approaches are proposed. Examples are effort estimation methods based on use cases [11] [20], and software size estimation in terms of FP from various UML diagrams [22] [7].
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This note was uploaded on 05/26/2011 for the course PM 199 taught by Professor Dr.atif during the Spring '11 term at University of Engineering & Technology.

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Effort Estimation of Use Cases for Incremental large scale softwares

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