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Re: Re: Re: Planning your software before writing

by chromatic (Archbishop)
on Jan 08, 2001 at 23:31 UTC ( [id://50554]=note: print w/replies, xml ) Need Help??


in reply to Re: Re: Planning your software before writing
in thread Planning your software before writing

Those are common criticisms of XP, and they're very understandable. I may not have explained it correctly, so I'll take a shot at clarifying. (I also don't mean to say that XP is a panacaea or suitable for everything. I'm just trying it with a couple of my projects, and it's working pretty well.)

It's not that design is hard, though it is, it's that up front design is very hard. That's why projects like the Gimp, Apache, Mozilla, and Slashcode are all facing fundamental rewrites. They invested some time in design before they started coding, but the uses and needs of their software grew beyond their original design. They designed themselves into a corner.

XP may or may not completely alleviate that -- it depends on your team's abilities. Instead, it says, "Design is good. Let's design all the time."

To address more of belize's post below, I'd take something like the Ultimate Bulletin Board, and write stories like the following:

  • Users must be able to post comments
  • Users should be able to see all comments arranged chronologically
  • Comments should strip out dangerous HTML
  • Moderators/administrators should be able to edit comments
  • Moderators/administrators should be able to delete comments
  • Users should be able to mark up their comments with smilies, bold, underlines, and italics
  • Users should be able to edit their comments
  • Moderators/administrators should be able to add their own markup
At some point in the future, you'll probably want to use a database for this, probably around the time you hit story 5. Are you going to bank on your ability to design the right db schema when you hit story two? XP would say that you should do as much as you can *without* adding that kind of infrastructure until you absolutely need to. Especially knowing that the requirements will change.

I, for one, would rather spend my resources completing the first few stories than building a database, arranging the tables just so, then having to modify the tables and convert the code four or five times. I'll probably have to do it once or twice, but the simpler the existing code and design by the time it is absolutely necessary to add the database, the less chaos there will be.

It's not a case of no design vs. full design, it's a case of design only as much as you need for the next two weeks vs. design everything.

One last what if... what if you spent a week designing the interface to a billing system your customer might want in a year, then he tells you that they have decided to use an existing front-end and want you to work on a batchloader? (Design what you need right now.)

  • Comment on Re: Re: Re: Planning your software before writing

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Re^4: Planning your software before writing
by Anonymous Monk on Oct 28, 2004 at 14:53 UTC
    Avoid using "SHOULD BE ABLE TO" when you write your stories in XP. Use "CAN" instead:

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