BDC:
It is a shared service that enables Office SharePoint Server 2007 to display business data from various back-end servers into a SharePoint page.
Business Data Catalog or BDC provides built-in support for displaying data with various webparts and list\list columns that can help in easy creation of dashboards with data from your SQL, web services, SAP, Siebel, or any other line-of-business (LOB) applications.
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