- The Customer: The customer is most typically the business analyst, executive, or client that is driving the production of software. They are the people who write the checks.
- The Architect: The architect is the person or persons responsible for designing how the system(s) work. They must take a holistic view and are responsible for guiding software to a place that is reliable, testable, efficient, and de-coupled.
- The Engineer: The engineers are those who actually build the software, who sit down and write code based on the customer's needs and the architectural designs.
- The Operator: Operators come in two very different classes: end-users and operations groups. If you release software for public consumption, your operator is the end-user. If however your software runs on company servers and/or workstations, then the systems personnel are the operators.
Hopefully no one has ever been in a position where all four of these sentences were true (or at least didn't have to work there long), but everyone's been involved in a job or project where at least one of them was. When one group wields too much say over the software development cycle, problems ensue. Each role should have autonomy in their own domain - their working environment should not be dictated to them by another role. However, for each role to enjoy such independence, there has to be a certain amount of give and take between them. For instance, if your engineers want to develop ASP.NET websites, the operators can't very well insist on Apache servers. If your operators are largely iMac owners, it would be unrealistic for the engineers to decide to write C# desktop apps. If the architect thinks it would be swell to use SharePoint, it's not his/her place to demand that the customer abandon the current CMS system they've come to know and love. Deciding how a piece of software (or software system) comes together requires negotiation and collaboration between the different groups.
One mistake commonly made is to assume that these roles have to be separate people. Naturally, in small companies, particularly start-ups, a small group of IT people will wear multiple hats. Freelancers, consultants, and one-man-IT-shops will often wear the architect, developer, and operator hats simultaneously and exclusively. There is a tendency, though, as the company grows, for these roles to become different departments. There's not necessarily anything wrong with that. But how a company sets up its reporting relationships should not determine how software development roles are filled. Software quality is improved and innovation is fostered when individuals who are engineers 90% of the time are allowed to be architects when the time is right. Architects who step into developer shoes produce more realistic systems. Operators who can be the customer sharpen system requirements. Fostering an environment where this kind of 'cross-pollination' is looked on favorably should certainly be a priority for all involved parties.
I once worked in the Information Systems Division of a Fortune 100 company. They had a lot of clumsy processes and a lot of the folks who worked there weren't standouts in their fields. But their environment was set up in such a way that each role had the autonomy they needed. An architectural group had created an overall vision for how the various systems should fit together, and the development groups were expected to follow that vision. However, inside their own domains, development teams had enormous flexibility in choosing the programming language, OS platform, and design patterns to use. The operators, the infrastructure teams that maintained the servers and terminals that ran this software, had a finite list of platforms and runtimes they would allow, but it was a long list, and anything on that list they would fully support.
My current job employs a much higher caliber of person, and has a much better development life cycle. They have, however, struggled with finding this correct balance between the stakeholders. Despite the flaws of that previous position, I find myself looking back at how they did things as a guide in this area. On paper, this sounds like a rather abstract and theoretical discussion, and in some IT shops it might be. But when this balance is off and/or these roles are not clearly defined, your workday can quickly transform into a series of turf wars. If you find yourself getting into that kind of situation, it's time to take a step back, define, and balance. We didn't, and it went badly: we thought we'd 'won' the turf war, only to have the problem come back at us sideways and make things worse. Don't let this happen to you!