Preprints Feast Workshop Iii

How do organizations use feedback to change their processes, and hence, improve their performance? A small working group isproposing that any organization under control almost always should be using feedback to stabilize and improve their products.We describe the results of applying the Feedback, Evolution, And Software Technology (FEAST) feedback model to ourwork on improving the software design process of 5ESS®. The translation of the study into a FEAST model took only a couple ofhours. The model concisely captures both managers and developers understanding of how the design process management teamcontrols the definition of the software design process. However, the model needs to be extended to ex plicitly show the lag timebetween the time when the control signal is sampled and reapplied back to the design process. Several other questions are posed asimportant discussion points to further improve the FEAST model. 1 5ESS BackgroundSoftware development as practiced at AT&T;'s 5ESS development organization can be visualized as consisting of five major steps:feature specification, software design, coding, testing, and delivery. A feature is a unit of functionality that can be sold tocustomers. It is the fundamental unit tracked by project management. Features may vary from a few NCSL and no hardware to50,000 NCSL with many complex hardware circuits developed specifically for that feature. Weider Yu et al. describe the 5ESSsoftware development p rocess and give examples of a feature in [3].On a large project such as 5ESS, hundreds of features are being simultaneously developed. These features are packaged together intoreleases that will be delivered to customers. Packages come in a spectrum of sizes that take anywhere from three to twenty-f ourmonths to develop. Features of all different sizes and complexities are packaged together, and so the development process of featuresfor a particular release are started and completed independently. This highly flexible approach to packaging customer features allowshigh feature development throughput and helps meet customer demands for customized features.Figure 1 shows pictorially how features start and stop relative to the stage of introduction of a process change. The heavy verticallines separate the three phases of process change; OLD, MIXED, and NEW. The horizontal lines with bars on either side showthe duration of the feature. The two problems are managing the mixed phase when more than one version of the process is in use.The other problem is assessing whether the new process is having the desired result especially when a representative sample offeatures is needed for assessment. FEATURESOLDMIXEDNEW Figure 1: The Assessment Problem. In this environment, process changes are generally introduced and made effective on a date, as opposed to by release. All features indevelopment at the date of the process change are either grandfathered to use the old process (usually due to a concern th at thechange would disrupt the feature development) or switched over to the new process. In general, all features already in the stage ofexecuting the old version of the process do not switch over to the changed process. This makes the actual date of a process changerather difficult to dete rmine on a global level; but, allows minimum disruption for the development process. 2 Model DescriptionThe FEAST project has proposed a fundamental process unit model consisting of input, output, feedback controller, and resourcesdisplayed in a simple diagram prescribed in the FEAST Manifesto [1]. On a sizable project like 5ESS, this model can be employedat several levels of abstraction:1 the global project level,2. globally at the development phase level,3 the individual feature level4 the individual developer level. 22/7/99, 1:36 pm25 -mml538-[FEAST] Figure 2 shows the 5ESS software design process cast literally into the FEAST model, an example of abstraction level 2. Design1. Developer decides tasks to do,then creates enacted task list2. Developer does designRequiredTask ListEnactedTask ListWaiveredTask List FeatureSpecificationDesign ProcessManagementTeam