Comments on: Common mistakes in software development (part 2): Mixing up the tiers

By: delphigeek

delphigeek — Thu, 30 Apr 2009 19:57:50 +0000

Интересный сайтик, узнал много нового….

By: kozminichna

kozminichna — Sun, 26 Apr 2009 17:57:11 +0000

Thank you author

By: David Daniel Hofmann

David Daniel Hofmann — Wed, 03 Dec 2008 02:12:11 +0000

Thanks for the article,
Believe me, I have seen bank’s pages generated from php with embedded sql code, I couldn’t believe that

By: rubenriojas

rubenriojas — Sun, 23 Nov 2008 19:37:50 +0000

Good post.

By: piampri

piampri — Tue, 18 Nov 2008 23:15:39 +0000

Nice blog btw

By: srinivasweb4u

srinivasweb4u — Tue, 18 Nov 2008 06:11:14 +0000

I came across. Thank you.

By: ivan

ivan — Sun, 05 Oct 2008 08:32:01 +0000

@chui tey As I see it age > 13 is a business rule so it has to be in the busines layer. you could do a couple of things to indicate that to the user.
you could call a validate method in the business layer that returns a list of error messages which you then display to the user in the Presentation layer.
It should definitely not be in the datalayer.because it has nothing to do directly with saving/updating or fetching data.

By: Chui Tey

Chui Tey — Sun, 05 Oct 2008 07:47:54 +0000

If you had to make sure age > 13,

Q1. would the code be in the data layer, the business layer or presentation layer?

Q2. If it’s in the business layer, and the user typed age = 11, how do you tell the user that he has to enter age >13 ?

Q3. Should the age>13 validation be in the data layer, inside INSERT or UPDATE triggers?

By: yteslax

yteslax — Fri, 03 Oct 2008 08:50:03 +0000

“This goes back to the guidance that can be found on the msdn website. This type of architecture is often used in combination with data sets but not in my example for this post.”

Yes one of MS way of dealing with data is using data sets. But when we talk about separation of concerns to satisfy loose coupling this data set approach breaks all. If you use data sets it’s not too meaningful trying to separate tiers… Whatever you do you’ll be get stuck in the end.

By: ivan

ivan — Fri, 03 Oct 2008 06:29:35 +0000

@bob I use this series to vent frustrations I have to deal with on a daily basis. And if they really were 1998 how come people still violate these simple rules. If you bear with me there will be some more current posts coming too. There are obvious problems with this architecture but I’ll return to that later.

@Andy Fisher. You’re absolutely correct and I should have put that distinction in. Thanks for your comment