IDEnumerator – This method is used to crawl and search Business Data Catalog data sources.

When you setup a SharePoint search crawl going on your BDC content source, MOSS will first of all execute the IDEnumerator method of each Business Data Catalog entity. This method simply returns a list of all identifier values of the BDC entity. Then, the crawler will execute the Specificfinder for each identifier value returned - using that identifier value as the input parameter to ensure a single row of data is returned each time the SpecificFinder method is executed.