>Trey,
>
>Let's assume for a moment that the data store is a tier. I have not read any substantive material that includes the data store as a tier. However, that does not make that issue fact or fiction. So, let's go with it.
>

All the descriptions I've ever read about n-tier business application development has included the data store as the final tier : 3-tier always means UI-Business-Database; 4-tier always means UI-Business-Data Services-Database.

I haven't seen them, so I'd be interested in reading some of the articles (etc) that don't substantiate this. Do you have any links for these? [real question - no sarcasm intended] I do have some to support my stance - I'll have to post them later, as I don't have them handy from my current location.

>Further, the powers of the language have to be served to the outside world by the data store tier. Clearly, this would knock out a text file.
>
>Would SQL Server pass muster? Yes. SQL Server is capable of exposing stored procedures to clients. You can have access to these items via ODBC, OLE-DB, etc.
>
>Would Fox pass muster? I don't think so. Stored procedures are not exposed. There is a very limited subset of the language that is exposed in the ODBC Driver. Sure, you could write a DLL to accomplish a lot of this work. However, that would be in the context of a data-services tier, not the data store tier.
>
>FWIW, I think this is the start of a convincing argument for why Fox-Data would not qualify as data-store tier - assuming such a tier really existed...
>

Almost everything I've read about developing n-tier apps states that using stored procedures or any other language specific items in the database tier is *not* recommended, in order that any data store can be used for this tier, and be switched out for another "at will."
The arguments I've usually seen made for using SP's is RI triggers or data maintenance - which are usually run directly against the DB app (e.g., in PL/SQL for Oracle) or by a scheduler within the DB app, and not by an external application or tier.
Any other data retrieval/updates to this data store should be done by the data services tier through SQL calls into the DB.

This would put Fox right back in the game since it does give access via SQL calls from ODBC - which is all what I've ever read seems to encourage.
I don't see stored procedure accessibility as an issue, since in my experience SP's are best used in VFP for RI triggers or default value functions, which do not need any public access.

>Assuming for the moment that the argument is bunk, is there a way we can construe that Fox-Data would count as a 4th. tier. You cannot use the USE statement since that is driven by the UI. You cannot use the USE statment in a middle-tier DLL since the UI cannot "see" the cursor.

Agreed. The UI would not use USE directly against the database tier, since that would break the n-tier design.
USE wouldn't be the way to get at the data from a middle-tier, anyway, since you should use SQL calls from the data layer - in keeping with the aforementioned capability to hot-swap a database tier.

>You could use ADO. However, if all of your tiers are in Fox, my question would by "why would you do this?" If you are in Fox anyway, why not take advantage fo what Fox offers?
>
>

As far as doing all 4 tiers in VFP at once - "can" and "should" are 2 different things. <bg>

My argument here was not what was best, it was simply that VFP "can" do all 4 tiers all by itself, as opposed to other languages, which can do the UI, Business and Data Services layers well, but in and of themselves cannot add the data store tier - they must connect to another application for this.

Of course - if you're writing an all-VFP app, why break out into 3 or 4 separate tiers or use ADO when having a 1 or 2 tier (meaning C/S) app all in VFP would be much more powerful?
The only good reason for VFP developers to do this would be to practice keeping the separate tiers truly separate, by coding each in the language that they feel most comfortable with, before adding other languages to their arsenals.

>Your thoughts...
>
>< JVP >
>
>
>So,
>
>Tier 1 = Interface
>Tier 2 = Business Layer
>Tier 3 = Data Services
>Tier 4 = Database
>
>I'll see Doug's 3 and raise 1 <g>
>
>So what else but VFP can do all *4* tiers?

Insanity: Doing the same thing over and over and expecting different results.