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Business Natural Languages Development in Ruby



Jay Fields presents his concept of Business Natural Languages (BNL). BNLs are a type of Domain Specific Language, designed to be readable by any subject matter expert, which allows to create maintainable specifications and documentation. The example language is shown using Ruby.


Jay Fields is a software developer at ThoughtWorks. He is a early adopter who is constantly looking for new exciting technologies. His most recent work has been in the Domain Specific Language space where he delivered applications that empowered subject matter experts to write the business rules of the applications.

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Recorded at:

May 08, 2008

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Community comments

  • BNL or simple UI

    by Michael Niv,

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    I enjoyed the presentation. Thanks!

    Two related questions:

    1. If I understand correctly, the system is not forcing the user to type syntactically-well formed string in some controlled grammar. Instead, the regexes do the magic under the hood. If so, does/could it happen that the business user naively uses a novel language construct (and instead of or, or a meaningful "not" or "could" instead of "does") which the BNL designer did not anticipate, but which get swept up in general regexes, and the meaning is harmed in some subtle way that may be hard for a business user to defend against using the testing tools available?

    2. Given the narrowly targeted domain specificity of the language, a similarly targeted UI might work as well. for example:

    compensate $ [number] per [enum: $1M-profit, deal] if
    [enum: gross, recent_deals, all_deals] exceeds [number]

    (where the stuff in square brackets is shorthand for the appropriate HTML form-tags)

    Do you have insights as to which circumstances favor a UI vs BNL?

    Thanks again!

    Michael Niv.

  • Re: BNL or simple UI

    by Jay Fields,

    Your message is awaiting moderation. Thank you for participating in the discussion.

    Hi Michael,

    Like almost everything in software: it depends. There are so many ways to translate external DSLs to executable code that it will depend on which solution you go with. If you have a strong security (or just general) concern you can use something such as TreeTop to create an entirely external DSL and pretty much entirely mitigate the risk. On the other hand, if you do something as simple as replace spaces with dots, then you are allowing for potential issues. Of course, those issues might be acceptable given timelines, trust, etc.

    Using form elements instead of a DSL is a commonly discussed option. I think it generally depends on how dynamic the language is. For example, I always thought trying to create SQL statements with forms was dreadfully painful. I would go with forms when possible, but if things are dynamic, I would quickly start considering a language.

    For example, my current project allows you to specify the following conditions:
    Date Range is 5/10/99
    Date Range is from 4/10/99 to 5/10/99
    Profit is greater than X
    Profit is less than X
    Profit is X
    Cost is greater than X
    Cost is less than X
    Cost is X

    And, so on, for many different conditions. This is something dynamic enough that it's painful to do in forms.

    I hope that's helpful, please shoot me another question if you want more info.

    Cheers, Jay

  • Re: BNL or simple UI

    by Sergio Diaz,

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    This thing of DSL isn't new at all, and here is an experiment that might offer some insight about.

    I remember reading Lisp's books from the 90's where the term DSL was about the actual jargon used by the business people. All of this in the context of Analysis and collecting requirements

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