There are two topics mixed together under "pointers" in my mind. 1) data contains a "pointer" or "address" in a given location, and we want to abstractly describe things like how big it is. For example, if my file format comes from a C language struct containing: int x; char* y; how big is the char* element 'y' anyway? Could be 4 bytes, could be 8 bytes. 2) reconstructing the pointer relationships within data. That is, the data is conceptually a graph of objects with pointers to each other. We want not only to access these pointers within the data but be able to traverse them in order to reference other objects within the data. Now (1) in the absence of (2) is a matter of just expressing how big the data we'll be ignoring and skipping over is. This is pretty easy to resolve. (2) is trickier. I suggest a proposal for pointers in DFDL should begin with an analysis of the approaches to pointers in XML and XSD, in particular ID, IDREF - in basic XML unique, key, keyref - that is, what XSD calls "Identity Constraints" I'd like to see annotations to unique, key, and keyref allowing these logical XSD concepts to be mapped into addresses and pointers within the data. Mike Beckerle Architect, Scalable Computing IBM Software Group Information Integration Solutions Westborough, MA Mike Beckerle/Worcester/IBM@IBMUS Sent by: owner-dfdl-wg@ggf.org 09/02/2005 04:34 PM To "Robert E. McGrath" <mcgrath@ncsa.uiuc.edu> cc dfdl-wg@gridforum.org, owner-dfdl-wg@ggf.org Subject split into multiple topics - Re: [dfdl-wg] Issues: additional data types I'd like to split this topic into several distinct ones: Arrays - I have a placeholder for this in the doc. Opaque and "code" types are separate. This is related also to the concept of "open content". Enums Bitfields Pointers Mike Beckerle Architect, Scalable Computing IBM Software Group Information Integration Solutions Westborough, MA "Robert E. McGrath" <mcgrath@ncsa.uiuc.edu> Sent by: owner-dfdl-wg@ggf.org 09/02/2005 03:13 PM To dfdl-wg@gridforum.org cc Subject [dfdl-wg] Issues: additional data types Greetings, Here is an "issue" for the DFDL: additional data types that should be considered. Please see attached. --- Robert E. McGrath National Center for Supercomputing Applications University of Illinois, Urbana-Champaign Champaign, Illinois 61820 (217)-333-6549 mcgrath@ncsa.uiuc.edu