Exploring the BDC Metadata Schema 
(Eric White) When developers are first getting started using BCS, they typically use SharePoint Designer (or perhaps Visual Studio 2010) to put together their BCS model. Using either of those tools, it is pretty easy to discover an external data source, and follow the appropriate steps to connect BCS to the data source and create an external content type (ECT). This is great for the most common scenarios.
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