We're about to embark on a fairly large integration effort to kill off a bunch of Access and Sql Server databases and get everything into one coherent enterprise system. There are also a number of other systems (accounting, CRM, payroll, MS Exchange) that hold critical data that we need to integrate (use for data validation in other systems), report on and otherwise expose. It is likely that some of these systems will change in the next few years, so we need to isolate our systems to be ready for change.

Ideally we would be able to expose our forms in a consistent manner across as many of our our systems as possible without having to re-develop them for each system. We are currently targeting SharePoint (2007 and soon 2010), Office (2007 and soon 2010 - Word, Excel, PowerPoint and Outlook), Reporting Services, .Net console applications, .Net Windows applications, shell extensions, and with the possibility of exposing some functionality on mobile devices (BlackBerries currently, maybe iPhones later) and via our website.

We're moving development to Visual Studio 2010 (from 2005) ahead of migrating to SharePoint 2010 and Office 2010. Given that most of our development is presently targeted to the .Net framework (mostly in C#) it seems logical to stick with this unless there is some compelling reason to switch frameworks/platform for some aspects.

We're thinking of your standard Database->Data Integration layer->Business Objects Layer->Web Services (or REST) layer->Client Application plus doing our own client application with WPF (or something else?) forms that can also be exposed in the MS systems (SharePoint, Office, Windows).

So, we don't want much, just everything :) Basically we need to isolate ourselves from database and systems changes, create an API that can be used throughout our systems and then make this functionality available in our client applications.

I'm very keen to get pointers from anyone who has tips on how to pull this off. Should we look at the Enterprise Library as a place to start? Is REST with ASP.Net MVC2 a better solution than Web Services for a system like this? Will WPF deliver forms re-use or is there something better?