The Data File Library is a tool used to read and write "flat" files. It allows you to work with the flat file data in a more natural way using generic objects similar to the Entity Engine GenericValue object.
The design is very similar to the Entity Engine in that there is an XML configuration file that is used to specify the format and structure of the flat file and a generic API used to deal with the records in the file. One major difference is that datafile records are hierarchical and a record can have various sub-records. The descriptor file is also structured this way so that each record type can have a parent record type.
When the file is read the library will convert strings of various formats and styles into numbers, dates, etc. It also supports common flat-file formats such as zero padded numbers, implied fixed decimal point numbers, and dates with no delimeters.
We apologize for the lack of further documentation on this. For more info see the datafiles.dtd file, or throw us an email to let us know that there is further interest in documentation for this component.