To me creating the application definition file is best categorized as the "necessary evil" required to unleash the functions of the BDC…
“The Business Data Catalog feature of Microsoft Office SharePoint Server 2007 provides an easy way to integrate business data from back-end server applications.” Thus begins the overview section on the BDC on MSDN. Although I think a one word removal from the sentence above makes it more accurate (I'll leave it to the reader to determine the offending word) this is a good summary and a good place to start. What the BDC has done has provided a standard way to get at data. This is very good. As we learned when writing custom web parts is tedious and this way we have an “approved” and consistent way of getting at the data. The bad news of course is that you REALLY have to like XML to like working with the BDC J
After spending some “quality time” with the BDC and reading the posts on many of the BDC support boards it is clear that there is a sense in which the BDC is “half-baked”. It will do what it says it will do, but not in a way that is necessarily easy or straight forward to implement. It also seems to work best with simple, demo-type examples.
The first issue is/was clearly the creation of the XML files. This was extremely tedious to do by hand and screamed out for a 3rd party product, (which several are available) before Microsoft introduced their own via the Microsoft Business Data Catalog Definition Editor (sort of rolls off the tongue doesn't it?).
My first impression of the MBDCDE was somewhat spoiled when I found out it could not support multi-part tables (e.g. schema.object ; employee.address) without giving me an error (which really is difficult because many apps use this notation for all their tables). Not sure if this has been fixed or not but no word on any of the boards that I have seen.
IMHO, there are enough issues with the MBDCDE that make 3rd party solutions still viable if you are going to be doing a lot of this work. (In our case, we had so many needs regarding data that we went a different route than the BDC, more on that in a different post.) But I have heard stories of 5000 line configuration files built by hand so obviously some folks can do it. My short attention span and lack of patience (the same error message can mean soooo many things) has made this route a non-starter for me. It will be interesting to see where MS goes with this whole idea of massive XML configuration files to define data access in the future.
Out of time for now.more to come on this topic soon. In the mean time I would be interested in others impressions, successes, failures, etc. creating XML configuration files.
mikec