12 January 2012

What is the Origin of the term "Functional Requirements"

I have been over editing Wikipedia again.  This time on Functional Requirements.

Yes, it's the poor quality that revolves around the Requirements and analysis topic that drew me in.  Wikipedia's content in this space is a classic example of the plumber with leaky pipes syndrome.  Each time I see it I just can't help myself.  I have to edit.

But this time I am stuck.

My question for you dear reader is this;

Where does the idea of the Functional Requirement (as opposed to just a plain ol regular requirement) come from?  What is the origin story of this mystical term?

And while I am here, can you share your view on what the essential elements are that make a requirement "functional?"

Thanks in advance,


  1. The Robertsons give a solid overview of the differences between requirement types in the abstract for the Volere Requirements Specification Template (http://www.volere.co.uk/template.htm).

  2. Luke - good to hear from you. Hope you are well and enjoying yourself in the northern winter :)

    I grok the differences - wondering WHERE the terms came from. Any ideas?

  3. Interesting question, something google or bing is not much help with. In fact a bing search returns this post of yours!

    Here is a follow-up question... what is the earliest known article or book (that can be found, of course) on Requirements? For example,I used to read the old, big Computerworld paper back in the 80's and used to make copies of interesting articles, but all have been disposed of over time... A lot of it was about methodologies, separating analysis from design and construction, but can't recall if the word "Requirement" was actually used...

  4. You have your functional and non-functional requirements. Functional requirements describe the required functionality of the application. And the non-fuctional describe the things like performance, security, etc.

  5. I went digging on google scholar and the uni library and found some good stuff.

    The earliest reference I found was a conference paper from 1982, which I could not get my hands on;

    R. T. Yeh, "Requirements Analysis- A Management Perspective," Proc. COMPSAC '82, Nov. 1982, pp. 410-416

    And the next earliest I found was from 1985;

    Roman, G.-C. "A taxonomy of current issues in requirements engineering" Computer, April 1985
    Volume: 18 Issue: 4 pp 14 - 23, ISSN: 0018-9162

    I read the later and was amused to see how little things have changed. In it he quotes Yeh as presenting the concept of Functional and Non-Functional as distinct categories for requirements.

    You're welcome :)

  6. ah, you must have an IEEE or ACM subscription... Did Roman have any other references in the article?

  7. I never thought about that! Thanks

  8. The article is a good one. I'd recommend shelling out the few bucks to read it.

    I emailed him as well and he's still researching in the space.

  9. Functional Requirements are very thoroughly considered and discussed in the design methodology called Axiomatic Design. A place to start reading about this is http://www.axiomaticdesign.com/technology/value.asp but there are many books and free articles on that website too that go more deeply into it. As someone whose been working with Axiomatic Design for several years, it's amazing to me that apparently Business Analysts don't know of this huge body of knowledge that helps so much in the requirements analysis process!

    Julie Carignan