This section of the Writer Directives DEF statement defines the attribute types for a table.
Refer to Salesforce’s Standard and Custom Object Basics documentation at http://www.salesforce.com/us/developer/docs/api/Content/sforce_api_objects_concepts.htm for a list of valid attribute types.
Note: Reading and writing base64 attributes is not supported. The Salesforce Reader/Writer uses the Salesforce Bulk API, which does not allow access to fields of type base64. The Salesforce Reader/Writer will ignore such fields, and warn of their presence.