Greetings, Thanks for the updated draft! Now there is lot's of flesh on the bones. I have a very basic question (or maybe 2). Perhaps this has been discussed but simiply omitted from the document. On page 19, Section 12.2. of the 8-26 draft: "The primary purpose of complex types in a DFDL implmentation is to determine where their sub-elements begin and end in the data stream." 1. What is the definition of "a DFDL implementation"? (I suspect this is something like 'a program that uses DFDL schema to interpret a data object') 2. What is the definition of "the data stream"? The document seems to have many unstated assumptions about data streams, they seem to be continuous arrays of bytes, etc., they are byte addressable, etc. In other places, there are references to "a data file" p. 26, p. 27, and so on, and seems to assume that "stream" and "file" are the same thing. This becomes an issue when the stored representation 'on disk' isn't the same as the IO stream, e.g., data from a relational database. It would be good to try to clearly define these terms, perhaps with a model of IO WRT what DFDL is describing. Thanks for your attention. --REMcG --- Robert E. McGrath National Center for Supercomputing Applications University of Illinois, Urbana-Champaign Champaign, Illinois 61820 (217)-333-6549 mcgrath@ncsa.uiuc.edu