IT and Engineering Insight: Control architecture, who needs it?
If you have a large control software programming project and no control system architect, small changes can lead to dead ends and bad decisions.
One of the bad habits of unsuccessful software programming projects, mentioned in the August “IT and Engineering Insight” column, is the lack of a system architect or a well-defined architecture. Without an architecture providing a controlling influence, small changes will accumulate during project execution, too often leading down dead ends or to bad decisions. To paraphrase Lewis Carroll: If you don't know where you are headed, then any direction seems like the right path. [Online extra - Also read, below: Don’t be duped; Is it marketing or a unified modeling language?]
Having an architect for a control software or manufacturing IT software programming project may seem like a waste: an architect will not generate code, write detailed design documents, write test cases, or execute tests. However, not having architecture involvement has doomed many projects from their start. Software guru Grady Booch said it best “ …every system has an architecture - most are accidental, some are intentional.”
Architecture or architect?
All control system projects need well-defined architectures, but not all projects need architects. Those that are big enough, or different from previous projects, do need involvement of a control system architect. Medium size projects often require part time architect involvement, and large projects often require a full-time architect or an architecture team. Small projects, where the problem is well understood, may not need an architect’s involvement. Small projects do, however, still need an architecture. Consider building an office building; you need an architect and a well-defined architecture or else you will have a lot of demolishing, rework, and remodeling to do. If you are building a tree house, you don’t need an architect, but you still need an architectural plan, even if it’s on the back of an envelope.
At the start of a project the primary role of the control system architect is to develop a precise and clearly understood vision of the entire system. The system should define the main elements of the design, the top level design requirements for each element, and the interfaces between elements. A good architect will continually evaluate the system architecture during development to ensure it is still valid. This means that the architect must be involved in all design reviews. The architect’s primary role during project execution is to review preliminary designs, detailed designs, and changes requests. The architecture provides guidance that keep problems from arising due to incomplete understanding of requirements, bad designs, hidden connections between elements, and incompatible changes in requirements.
Get a reasonable expert
Identifying an architect or assigning the architect role to someone is an important first step in a project. An architect must be a jack-of-all-trades. The architect must be a reasonable expert in databases, networks, programming languages, programming styles, and the application area. An architect needs to understand software engineering as well as the specialized tools for documenting and verifying architectures. If the project is a control system project, then a control system architect is needed to know all of technologies listed above and also needs to know HMI, PLC, and DCS programming languages, data historian architectures, and industrial networks.
Picking a team member and assigning that person the architect role is bad project practice. Like any skill, being an architect takes practice and specialized knowledge. Grady Booch also said, “The best software designs look simple, but it takes a lot of hard work to design a simple architecture.”
Unsuccessful projects will often fail to have anyone clearly assigned to the architect role or will not have a well-defined architecture. Having a detailed architecture specification or an identified system architect will not make a project successful, but lacking both will leave your project “out-of-control.”
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Also see: How to Avoid Project Failure.
ONLINE extra: Don’t be duped: Is it marketing or a unified modeling language?
How do you know if your project has a well-defined project architecture? Unfortunately, if you have to ask, then the answer is probably “No you don’t have a well-defined architecture.” If you have an architecture, make sure it not really a “marketecture.” A Marketecture (marketing-architecture) is the marketing departments attempt at an architecture. Markectectures are usually PowerPoint presentations, developed by marketing for sale engineers to explain the main elements of a system. They look pretty, but don’t have any of the detailed interface and functionality information of a real architecture. If your architecture specifications consist of marketing slides, then you have a marketecture, not an architecture.
Real architectures may be formally defined or informally defined. If they are formal, then they are often described using the UML (Unified Modeling Language - ISO/IEC 19501) architecture components of packages, package diagrams, component diagrams, and deployment diagrams. Informal architectures will use boxes to represent individual elements and lines to represent integration points of data or control flow. Each element must have a clearly defined function, interface, scope, timing requirements, and restrictions. Each integration point must have a clearly defined list of data elements that make up the data or control flow, and should identify the amount and frequency of the information exchange. If your architecture diagrams and documents lack these critical pieces of data, they are probably marketecture diagrams and will not provide the controlling influence required for an “in-control” project.
Project management versus an architect
One common mistake in software programming projects is to assume that the project manager can be the architect. Project managers have many important personnel and scheduling tasks to perform when running projects, leaving little time to evaluate designs and detect future problems. Another mistake is to let the developers “work out the architecture.” This leads to inconsistent module designs and interfaces, usually resulting in significant rework and redesign late in the project.
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