Here are a few tips and tricks to remember when dealing with Business Data Catalogs (BDC):

• When you try to import invalid metadata, the Business Data Catalog displays an error message explaining the problem, and provides the line number where the error occurred. It is helpful to open the XML in Microsoft Visual Studio 2005, use the Go command (Edit menu) to locate the line where the error occurred, and then review the XML statements near that line.
• Business data in lists and Business Data Web Parts are driven by Business Data Catalog permissions.
• When you author metadata, try to import one entity at a time so that you can identify and debug problems more easily.
• The minimum permission you need on an entity to use it in clients is the Selectable in Clients right.
• Site Settings has little relationship with Business Data Catalog permissions.
• The Business Data Catalog provides a schema definition file (XSD) that defines the schema allowed in the XML file, and that defines the metadata for a business application. It is important for the XML documents to adhere to this schema.

You can find the BdcMetadata.XSD file in the \Bin directory of your Microsoft Office SharePoint Server 2007 installation, typically at <Root>\Program Files\Microsoft Office Server\12.0\Bin.

• When authoring metadata in Microsoft Visual Studio 2005, copy the .xsd file to the working folder and set the SchemaReference attribute in the XML file to point to the .xsd file in the working folder. As a result, Visual Studio provides IntelliSense, which greatly simplifies editing.
• Another name for the Business Data Catalog is “Application Registry”.
• You must read the Business Data Catalog: Metadata Model section and understand how to write each metadata element. The topics also list supported children and properties, and their limits and accepted values.
• The UserContext filter appends the current Microsoft Windows user’s domain name and user name to the method call.
• The View permission controls the user’s ability to view the data associated with the entity, in contrast to the user’s ability to view all metadata objects all the time. The applications and entities are viewable in the UI by default. The View permission is equivalent to having the Execute permission to execute methods on an entity or an entire application.
• ULS log files (created every 30 minutes) contain a copy of the event log information and the stack trace. You can find the log files in the following path: <drive>\Program Files\Common Files\Microsoft Shared\web server extensions\12\LOGS. ULS log files contain useful information about all the run-time exceptions and can help you identify problems.
• An easy way to find Business Data Catalog–related messages is to search for “metadataexception”, “ApplicationRegistry”, or “Exception” in the Message field, and then look under the Business Data category.

Additional Resources:

• Business Data Catalog FAQ
  
• Troubleshooting Business Data Clients and Metadata
• Business Data Catalog Security Trimmer
• AccessChecker Samples
• Business Data Catalog: Metadata Model
• AdventureWorks SQL Server 2000 Sample
• SampleWebService Metadata