Friday, August 19, 2011

Don’t Separate Design from Implementation

I was a programmer for about fifteen years. Then I managed a factory IT department for a few years, and managed vendors delivering software for yet more years.  In all of those years (with one exception), software was delivered on time and customers were happy. Yet I never used a list of detailed requirements, let alone a backlog of stories, to figure out what should be done – not for myself, not for my department, not even for vendors.

In fact, I couldn’t imagine how one could look at a piece of paper – words – and decipher what to program. I felt that if the work to be done could be adequately written down in a detailed enough manner that code could be written from it, well, it pretty much had to be pseudocode. And if someone was going to write pseudocode, why not just write the code? It would be equally difficult, less error-prone, and much more efficient.

Software Without Stories
So if I didn’t use detailed requirements – how did I know what to code? Actually, everything had requirements, it’s just that they were high level goals and constraints, not low level directives. For example, when I was developing process control systems, the requirements were clear: the system had to control whatever process equipment the guys two floors up were designing, the product made by the process had to be consistently high quality, the operator had to find the control system convenient to use, and the plant engineer had to be able to maintain it. In addition, there was a deadline to meet and it would be career-threatening to be late. Of course there was a rough budget based on history, but when a control system was going to be used for some decades, one was never penny wise and pound foolish. With these high level goals and constraints, a small team of us proceeded to design, develop, install, and start up a sophisticated control system, with guidance from senior engineers who had been doing this kind of work for decades.

One day, after I had some experience myself, an engineering manager from upstairs came to ask me for help. He had decided to have an outside firm develop and install a process monitoring system for a plant. There was a sophisticated software system involved – the kind I could have written, except that it was too large a job for the limited number of engineers who were experienced programmers. He had chosen to contract with the outside firm on a time-and-materials basis even though his boss thought time-and-materials was a mistake. The engineering manager didn’t believe that it was possible to pre-specify the details of what was needed, but if a working system wasn’t delivered on time and on budget, he would be in deep trouble. So he gave me this job: “Keep me out of trouble by making sure that the system is delivered on time and on budget, and make sure that it does what Harold Stressman wants it to do.”

Harold was a very senior plant product engineer who wanted to capture real time process information in a database. He already had quality results in a database, and he wanted to do statistical analysis to determine which process settings gave the best results. Harold didn’t really care how the system would work, he just wanted the data. My job was to keep the engineering manager out of trouble by making sure that the firm delivered the system Harold envisioned within strict cost and schedule constraints.

The engineering manager suggested that I visit the vendor every few weeks to monitor their work. So every month for eighteen months I flew to Salt Lake City with a small group of people.  Sometimes Harold came, sometimes the engineers responsible for the sensors joined us, sometimes the plant programmers were there. We did not deliver “requirements;” we were there to review the vendor’s design and implementation. Every visit I spent the first evening pouring over the current listings to be sure I believed that the code would do what the vendor claimed it would do. During the next day and a half we covered two topics: 1) What could the system actually do today (and was this a reasonable step toward getting the data Harold needed)? and 2) Exactly how did the vendor plan to get the system done on time (and was the plan believable)?

This story has a happy ending: I kept the engineering manager out of trouble, the system paid for half of its cost in the first month, and Harold was so pleased with the system that he convinced to plant manager to hire me as IT manager.

At the plant, just about everything we did was aimed at improving plant capacity, quality, or throughput, and since we were keepers of those numbers, we could see the impact of changes immediately. The programmers in my department lived in the same small town as their customers in the warehouse and on the manufacturing floor. They played softball together at night, met in town stores and at church, had kids in the same scout troop. Believe me, we didn’t need a customer proxy to design a system. If we ever got even a small detail of any system wrong, the programmers heard about it overnight and fixed it the next day.

Bad Amateur Design
The theme running through all of my experience is that the long list of things we have come to call requirements – and the large backlog of things we have come to call stories – are actually the design of the system. Even a list of features and functions is design. And in my experience, design is the responsibility of the technical team developing the system. For example, even though I was perfectly capable of designing and developing Harold’s process monitoring system myself, I never presumed to tell the vendor’s team what features and functions the system should have. Designing the system was their job; my job was to review their designs to be sure they would solve Harold’s problem and be delivered on time.

If detailed requirements are actually design, if features and functions are design, if stories are design, then perhaps we should re-think who is responsible for this design. In most software development processes I have encountered, a business analyst or product owner has been assigned the job of writing the requirements or stories or use cases which constitute the design of the system. Quite frankly, people in these roles often lack the training and experience to do good system design, to propose alternative designs and weigh their trade-offs, to examine implementation details and modify the design as the system is being developed. All too often, detailed requirements lists and backlogs of stories are actually bad system design done by amateurs.

I suggest we might get better results if we skip writing lists of requirements and building backlogs of stories. Instead, expect the experienced designers, architects, and engineers on the development team to design the system against a set of high-level goals and constraints – with input from and review by business analysts and product managers, as well as users, maintainers, and other stakeholders.

A couple of my “old school” colleagues agree with me on this point. Fred Brooks, author of the software engineering classic “The Mythical Man Month” wrote in his recent book “The Design of Design” [1]:
“One of the most striking 20th century developments in the design disciplines is the progressive divorce of the designer from both the implementer and the user. … [As a result] instances of disastrous, costly, or embarrassing miscommunication abound.”
Tom Gilb, author of the very popular books “Principles of Software Engineering Management” and “Competitive Engineering” recently wrote [2]:
“The worst scenario I can imagine is when we allow real customers, users, and our own salespeople to dictate ‘functions and features’ to the developers, carefully disguised as ‘customer requirements’. Maybe conveyed by our product owners. If you go slightly below the surface of these false ‘requirements’ (‘means’, not ‘ends’), you will immediately find that they are not really requirements. They are really bad amateur design for the ‘real’ requirements…. 
"Let developers engineer technical solutions to meet the quantified requirements. This gets the right job (design) done by the right people (developers) towards the right requirements (higher level views of the qualities of the application).”
Separating design from implementation amounts to outsourcing the responsibility for the suitability of the resulting system to people outside the development team. The team members are then in a position of simply doing what they are told to do, rather than being full partners collaborating to create great solutions to problems that they care about.

[1] “The Design of Design” by Fred Brooks, pp 176-77. Pearson Education, 2010
[2] "Value-Driven Development Principles and Values;" by Tom Gilb, July 2010 Issue 3, Page 18, Agile Record 2010 (