Robert F. Rose - Software Development Activity Cycles: Collaborative Development, Continuous Testing and User Acceptance

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The first computer I ever saw was playing Jingle Bells. It was 1958, on the ground floor of the DuPont engineering building near Wilmington, Delaware. The Univac computer was built around vacuum tubes and solenoids that buzzed and hummed while computing. A group of engineers, clearly making use of any free time, wrote a nonsense program that matched the noises to Christmas carols. I was mesmerized.

My career in IT did not begin until a decade later in 1969 as a FORTRAN programmer. I started building systems in 1976. My first system was a small Management Information System (MIS) that was concluded with great success. My second effort was a system an order of magnitude more complex. After one flop at the start, it was completed but never deployed giving me a strong sense of project risk.

I started thinking about the process of developing software in the 1980s to respond to the technical approach section of various RFPs (requests for proposals). The DPAC model has evolved from that process through my direct participation over 35 years in six software development projects. There was no direct influence from other models. DPAC reflects my thinking since circa 1995; the DPAC model in its present form was copyrighted in 2015.

Having also participated as a technical troubleshooter cleaning up systems after the developers left the building, I experienced firsthand that many issues in support are directly related to the quality of the software development effort.

The model described herein represents a continuum beginning with inception into ongoing evolution. While retirement seems inevitable, there are systems that are still going strong through decades of use. Legacy systems may need to be enhanced to enjoy the delights of user-facing web and mobile experiences.

Another thing the DPAC model is designed to address is the derivation of functional requirements throughout the development process beginning with a Vision Statement and continuing into the Support Cycle. To that end, the cycles of activity in the DPAC model are represented as recursive and re-entrant, nested contiguous ovals. Each activity cycle is overlaid with an interpretation of the Deming quality control phases of Plan, Do, Check, and Act (PDCA).

A chart of D P A C with statement on the left and different cycles marked with each growing step. Process overview, process detail, unit development, service assembly, system integration, deployment and support cycle, which finally leads to retirement.

The DPAC Model

A model, as used in this context, is a graphic representation of the development processes. A tour through the DPAC model begins in Chapter are walk-throughs of the Elaboration, Construction, Assembly, and Evolution Stages, respectively. Each of these chapters begins with the model diagram at the top highlighting the part of the model the chapter describes and where it fits in the overall process.

Chapter contains Final Remarks.