Thanks Steve. Can't "offset formats" be handled in DFDL by using 2 passes?
I wonder if "recursive formats" can be handled using 2 passes? /Roger -----Original Message----- From: Steve Lawrence <[email protected]> Sent: Friday, January 25, 2019 1:41 PM To: [email protected]; Costello, Roger L. <[email protected]> Subject: [EXT] Re: Assertion: DFDL can parse/unparse every data format ... do you agree? There are definitely formats that DFDL cannot parse. Two general categories immediately come to my mind: 1) Recursive formats. DFDL v1.0 does not allow recursion in schemas, and so any formats that are recursive cannot be modeled completed in DFDL. For example, people have tried to model JSON in the past. It can be modeled, but only to an arbitrary depth. 2) Offset formats. Some formats specify offsets into data to determine where the next chunk of data is, sortof akin to random data access. An example of that is the TIFF format. DFDL has no way to support these types of formats. It's very possible that these two features will be added in future versions of DFDL and Daffodil, but as of today that is not possible. DFDLv1.0 also does not support layering (e.g. compressed data, line folding), but Daffodil has implemented an extension to support those kinds of features. - Steve On 1/25/19 9:23 AM, Costello, Roger L. wrote: > Hello DFDL community, > > I realize that there are some data formats that require two passes. > > Assertion: DFDL can parse and unparse every data format. Most formats can be > parsed in a single pass, the remaining can be parsed in two passes. > > Do you agree with this assertion? > > /Roger >
