[aosd-discuss] concerns and requirements

[Dean Wampler]

I find it very helpful to remember the distinction between the 
stakeholder's "mental model" of the problem domain and how you view it, 
using the technical tools of SW analysis and design.

I'm not sure I would even mention "concerns" vs. "requirements" to your 
stakeholders, because they probably don't think that way. They just 
think of everything as a requirement. Some of the requirements they give 
you will be for specific features, while others will be for "the other 
stuff", like performance, security, etc.  It's all the same to them. So, 
I would just get their inputs on what the system must do in the language 
they understand and then I would "parse" that information into a 
technical representation of concerns, feature requirements, use cases, 
object models, etc., etc.

For example, a banker might tell you "we need accounts for individuals 
that only they and our tellers can access through the web or an ATM. The 
customer must be able to deposit and withdraw money, but not overdraw 
the account. Oh, and we need to support up to 10,000 concurrent users."  
Right there, you've got (at least) two concerns, secure access and 
performance, plus a bunch of feature requirements for the logic of bank 
accounts.

Finally, there's a big discussion now about whether feature requirements 
themselves can be approached as aspects. Jacobson has suggested that use 
cases, which are the "Yin" to the requirements "Yang" (if I can make 
that analogy; those of you in the U.S. might prefer the Venus vs. Mars 
or the Ford vs. Chevy analogy ;^) are themselves aspects. If true (and 
it remains to be seen if this is really a practical approach...), then 
your feature requirements can also be mapped to use cases and hence to 
aspects.  You be the judge ;^)  Here's a link to Ivar's papers.

http://www.ivarjacobson.com/postnuke/html/modules.php?op=modload&name=PostWrap&file=index&page=PublishedPapers&meid=9
<http://www.ivarjacobson.com/postnuke/html/modules.php?op=modload&name=PostWrap&file=index&page=PublishedPapers&meid=9>
Dean
dean at aspectprogramming.com

Richard wrote:

> Hi all,
>     I think this topic which has been dealt with several times in this 
> discussion form but sorry for bringing it up again. I read some of the 
> previous archives about the relation between concerns and requirements 
> but i am still confused by this.
>     I am more of an application developer than an architect, so all of 
> my work was based on requirements of the stakeholder(s). This is 
> really confusing for me, as i am not sure if i should be identifying 
> the concerns from the requirements or should i be asking the 
> stakeholders to express the system in concerns in order to use AO? 
> More appropriately, the question is how do i explain to someone 
> what is the difference and/or similarity between concern and requirement?
>  
> Thanks & Regards,
> Richard
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