Re: What is analysis?

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Tue, 04 Dec 2007 17:03:47 -0400
Message-ID: <4755c0ba$0$5256$9a566e8b_at_news.aliant.net>

David Cressey wrote:

> "Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
> news:47558e4d$0$5265$9a566e8b_at_news.aliant.net...
> 

>>David Cressey wrote:
>>
>>>"Jon Heggland" <jon.heggland_at_ntnu.no> wrote in message
>>>news:fj1iog$vcc$1_at_orkan.itea.ntnu.no...
>>>
>>>
>>>>Quoth David Cressey:
>>>>
>>>>
>>>>>I don't think of "formal" as a code word for "scientific". In fact, I
>>>>>don't even think "engineering" is code for "scientific". Science is
>>>
>>>about
>>>
>>>
>>>>>discovery. Engineering is about invention. There is a lot of overlap

> 
> in
> 


>>>the

>>>

>>>

>>>>>language, the tools, the method and the mode of thought.  But they


>>>

>>>aren't

>>>

>>>

>>>>>interchageable.

>>>>

>>>>Yes, I was being sloppy. My (poor) defense is that the Norwegian word

>>>>for science ("vitenskap") is used rather more broadly than the English

>>>

>>>term.

>>>
>>>No problem. If I look up "ciencia" in a Spanish-English dictionary,

> 
> the
> 

>>>first meaning given is "science". But the second meaning given is
>>>"knowledge". That meaning is still in widespread use. I suspect that,

> 
> not
> 


>>>too long ago,  the same would have been true in English.

>>>

>>>

>>>

>>>

>>>>>And I'll accept that information systems evolve along with changing


>>>>>requirements.  But

>>>>>I'll also claim that some good analysis can accomplish in weeks when

>>>

>>>take

>>>

>>>

>>>>>months worth of iterative development.

>>>>

>>>>Yes, but despite my nifty definition, I still have a hard time

>>>>separating analysis and design/development. I find it very difficult to

>>>>imagine one without the other.

>>>

>>>I find it hard to imagine correct design/development without a correct

>>>understanding of the problem to be solved. Obtaining a correct
>>>understanding of the problem to be solved may be too informal a process

> 
> for
> 

>>>some people to give it a name like "analysis". Some people say they

> 
> just
> 

>>>sit down and chat with the users. But I think it's "analysis" whether

> 
> it's
> 

>>>a formal process or an informal one, and whether it's performed once at

> 
> the
> 


>>>outset of a project,  or repeated between each iteration of an iterative

>>>development process.

>>>

>>>

>>>

>>>

>>>>>It would be interesting to know if there is a way of deriving relvars


>>>

>>>from

>>>

>>>
>>>>>some form of data analysis that doesn't involve ER. I am convinced

> 
> that
> 


>>>a

>>>

>>>

>>>>>set of relvars embeds design decisions,  but I don't know from direct


>>>>>experience.  What do you say?

>>>>

>>>>Well, what do you mean by "design decisions"? Relvars and constraints

>>>>(including, but not limited to, keys and  foreign keys) represent

>>>>business rules. A specification of business rules seems like a natural

>>>>product of analysis to me. Of course, you could start with the business

>>>>rules and go to relvars from there.

>>>
>>>I agree. And a specification of all the business rules probably

> 
> captures
> 


>>>(at least)  all the information recorded in an ER model.

>>>

>>>Now it's time for me to ak a dumb question:

>>>
>>>What is a relvar?
>>
>>A variable whose value is a relation.
>>
>>
>>
>>>How is it different from a relational table?
>>
>>SQL has tables. Relvars are relational variables -- either stored or
>>derived or automatic or global or local etc.
>>
>>
>>
>>>Is the difference mainly one of terminology?
>>
>>No.
>>
>>
>>
>>>or is there a subtle concept here that I need to learn?
>>
>>The differences between tables and relations are not all that subtle.
>>Relvar was introduced to disambiguate between relation values and

> 
> variables.
> 

>>
>>>What benefit was derived by introducing the term "relvar"?
>>
>>It avoids confusion when discussing relation variables versus relations
>>ie. relation values.
>>
>>
>>
>>>When was it introduced?
>>
>>Circa Third Manifesto
>>
>>
>>
>>>Are relvars designed?
>>
>>Yes.
>>
>>
>>
>>>Could there be more than one set of relvars derived from the same set of
>>>business rules?
>>
>>Yes.
>>

> 
> 
> Thanks for all these answers, Bob.
> 
> Are tables not variables?  If not, why not?

If you are talking about named tables in an SQL database, yes, those are variables. Such a table is a variable as is a named view in an SQL database. Each holds or associates with a table value. Received on Tue Dec 04 2007 - 22:03:47 CET