Improving Estimations in Agile Projects: Issues and Avenues

From the mid ‘90s on, a number of Agile Methodologies have been proposed, most of them based on the basic values and principles summarised in the 2001 “Agile Manifesto”. These agile methodologies were aimed at small teams with severe project constraints (i.e. small project teams in the same location, the customer as a member of the project team, informal communication, test-driven approach, etc.). Compared to more traditional project methodologies, Agile (or Lightweight) Methodologies are more detailed on Construction and Testing practices, but much less specific about other topics, such as Estimation. Currently, in most Agile Methodologies the experience of the team represents the basis for estimating from the high-level requirements. The application of a Functional Size Measurement Method (FSMM) for estimation purposes raises a number of technical problems in Agile projects (i.e. unstable requirements, iterative SLC, non-functional requirements). A candidate solution is to combine an early sizing method for an agile project with a full FSMM method to be applied later in the SLC, when User Stories (the way XP labels high-level functional requirements) become available and are more stable. The goal of the paper is to identify estimation issues in the most known and adopted agile methodologies, looking at possible improvements at the organiseational level.