>>should conform to Single Threaded Apartment model threading. VFP6 actually
>>does conform to this model, but has internal blocking to prevent simultaneous
>>operation of method/property access.
>
>WOw... glad to know someone understands this.

Well, I've been boning up on COM for the last couple of years as part of
what makes Web Connection's COM interfaces tick <s>... There are a few
decent books out there. If you are interested in this stuff, I highly
suggest you start subscribing to Visual Basic Programmer's Journal. One
of the best sources for all issues COM...

>So, if they can block this an allow sumultaneous 'psuedothread' is MTS still not needed?

Whether you use MTS or not is not going to fix the problem, because regardless
of how you access that InProcess COM component it will block. In MTS it's
just another process that's blocking rather than your own calling process.
MTS is really a proxy that takes an incoming COM method call and routes it
to the actual object.

The only way you can get around the blocking issue is to not use InProc
servers. Single Use EXE files will give full simultaneous processing. If
handled smartly you can achieve good scalability with this model, which
is essentially what Web Connection does with COM backend servers.

>
>As you said, it seems to be the MTS is really only needed when doing homogeneous transactions or complex multi-object transactions?
>
>However, isn't another advantage to MTS the role based security?
>

Yes. There are a number of features of MTS that are nice, but you have to
ask yourself whether it's worth the overhead, lack of scalability and extra
development effort to achieve them. Role based security simplifies security
adminstration, but a proper security layout will solve that problem just
as well - it just means you have to understand the security model, which
is what MTS aims at eliminating.

A lot of features in MTS are that way - just about anything MTS does you
can do standalone. It'll just be more work. But even if it did work with
VFP as expected you'd still pay for it with overhead and potentially
complex development scenarios.

>Hmm... what to do... we are told three tier... but still deciding on how the middle will work. Is it possible to create a scalable 3-tier in VFP without using MTS or any other middleware?

MTS isn't a tier <s>. It's simply a hosting mechanism for x-tier components.
MTS isn't a requirement for multi-tier applications. The jest of 3 tier is
to isolate user interface, business rules and database. The key to make this
work is solid class design. Heck you can do proper three-tier development all
in VFP as long as you design it right. If properly designed the tiers can be
broken apart into separate COM objects (except maybe the UI layer).

BTW, I've been harking on MTS quite a bit in this thread. The reason for this
is simple. All the scenarios, examples and even newsgroup posts I've seen have
yet to show me *something* that MTS does that makes it worthwhile technology.

The reason many people implement MTS now is not because they need it, but
because they *think* they need it and because MS says it's the right thing
to do. I don't doubt MTS will eventually fill the needs of Enterprise
computing, but that time is certainly not now at least not yet.

Regards,