Iterative Development Royce, “Successful Software Management Style: Steering and Balance”, IEEE Software sep/oct Sp8Jan22iterdev2

Key Ideas and/or Questions 2 541Sp8Jan22iterdev2

Rationale of Iterative Development “Traditional project management approaches in software- intensive projects don’t encourage the steering and adjustment needed to reconcile significant levels of uncertainty in the ■ problem space (what the user really wants or needs), ■ solution space (what architecture and technology mix is most appropriate), and ■ planning space (including cost and time constraints, team composition and productivity, stakeholder communication, and incremental result sequences).” 3 541Sp8Jan22iterdev2

Measurement Just as the movie industry gets action on film, we too must get increments of software into executable form to make things tangible enough to assess progress and quality Sp8Jan22iterdev2

Results This iterative management style is results rather than activity-based. In the world of software, real results are executable programs. Everything else (requirements documents, usecase models, design models, test cases, plans, processes, documentation, and inspections) is secondary—simply part of the means to the end Sp8Jan22iterdev2

Precision vs Accuracy A common failure pattern is developing a five-digits-of-precision specification when the stakeholders have only a one-digit-of-precision understanding of the problem, solution, or plan Sp8Jan22iterdev2

Evaluation of these ideas 7 541Sp8Jan22iterdev2

What do we apply to 541 project? 8 541Sp8Jan22iterdev2

Iterative Rework: the Good, the Bad and the Ugly Richard E Fairley and Mary Jane Willshire, IEEE Computer, Sep Sp8Jan22iterdev2

Key Ideas and/or Questions Sp8Jan22iterdev2

Rework Incremental build lets developers produce weekly builds of an evolving product. Each iteration involves a certain amount of rework to enhance and fix existing capabilities (the good). However, excessive rework could indicate problems in the requirements, the developers’ skills and motivation, the development processes or technology used, or all of the above (the bad). Exorbitant levels of rework result in truly untenable situations (the ugly) Sp8Jan22iterdev2

Fig 3 – four dimensions Sp8Jan22iterdev2

Amount of rework For several years, our rule of thumb has been that total rework (evolutionary plus both types of avoidable) is acceptable at 10 to 20 percent of the total effort for each reporting period in an iterative development process. The reporting period typically varies from a week to a month. Weekly analysis of rework data is desirable in a project’s early stages. Less frequent reporting and analysis is appropriate once rework stabilizes and remains within the desired range Sp8Jan22iterdev2

Excessive rework Sp8Jan22iterdev2

Insufficient Rework Sp8Jan22iterdev2

Our Goal: Project Plan u The size and important features of the product to be produced u The division of tasks into iterations u Size and effort estimations of work tasks Sp8Jan22iterdev2

Identify Subtasks u Identify all the different subtasks necessary to achieve product –Include units if possible, e.g. number of ppt slides u For each subtask, identify milestone(s) and completion criteria u Establish dependencies Sp8Jan22iterdev2

Checkpoints, Milestones, or Inch- pebbles u “A checkpoint is an objectively identifiable point in a project” u e.g. not “coding is 90% complete” u possible – “design is ready for review, design has been reviewed by all team members.” u “a checkpoint for every five hours or so of work” Sp8Jan22iterdev2

Project Plan u establish subtasks (wbs) u establish checkpoints (wbs) u establish dependencies (gannt or pert) u establish dates (gannt chart) u assign subtasks Sp8Jan22iterdev2

Project Plan for Iteration 1 u Must have time in minutes for each leaf task u No leaf task can be more than 7 days before successor u Each leaf task must have completion criterion Sp8Jan22iterdev2

Thursday, Jan 24 u Read about Earned Value –Stellman and Greene “track the performance …” pp63-66 –SOS 3.7 – work through exercise 3.6 on page 36 – make sure you can get the same answers Sp8Jan22iterdev2