I think that the single most significant and powerful extension capability for DFDL would be to support attributes.
XML Schema is highly extensible already and widely deployed. JSON schema is pretty consistent and has similar expressive power - if ever finally standardized and consistently supported in tools, it might further broaden the available information-architecture infrastructure for many applications and much of the Web. The ability to align DFDL directly with any XML Schema, to support consistent mappings of diverse datasets with coherent data models, would be major increase in DFDL capability. p.s. long-held opinion: skateboards and attributes are not a crime… 8) all the best, Don -- Don Brutzman Naval Postgraduate School, Code USW/Br brutz...@nps.edu Watkins 270, MOVES Institute, Monterey CA 93943-5000 USA +1.831.656.2149 X3D graphics, virtual worlds, navy robotics https://faculty.nps.edu/brutzman From: Mike Beckerle <mbecke...@apache.org> Sent: Thursday, November 2, 2023 8:27 AM To: users@daffodil.apache.org Subject: Re: Proposal: Extensible DFDL I think extensibility would be great for DFDL. The DFDL workgroup punted on this as there was no such thing as an extensible format description language to generalize into a standard. We realized that unparsing was already breaking a lot of new ground, but it was a must-have feature. So we had to draw a line somewhere on the number of untested new concepts in DFDL or it would never get done. It took 20 years as is to become standardized. Some format description languages may have been implemented this extensible way, but that was not a visible user feature in any one that I ever saw. As a research effort this is a good idea. Daffodil is available for use in prototyping if that's useful, and if it turns out to be valuable it could be proposed for inclusion in DFDL in the future. Some years ago I suggested this to someone as a thesis topic for a CS PhD project, but to my knowledge it didn't go anywhere. On Thu, Nov 2, 2023 at 10:20 AM Roger L Costello <coste...@mitre.org <mailto:coste...@mitre.org> > wrote: Hi Folks, Consider this input containing a date time value: 20230926T124800Z We can design the DFDL, using the xs:datetime datatype and associated DFDL calendar properties, so that parsing produces this XML: <DateTimeIso>2023-09-26T12:48:00+00:00</DateTimeIso> That is beautiful XML - concise and precise. Next, consider input containing a lat/long value: 2006N-05912E It would be excellent if we could design the DFDL so that parsing produces this: <OriginOfBearing>20°06′N 059°12′E</OriginOfBearing> That is also beautiful XML. In fact, it is possible to achieve this! By hiding the input and then performing a bunch of transformations using dfdl:inputValueCalc. However, that's a terrible approach because, as Mike Beckerle often says, "DFDL is not a transformation language!" If only we had a latlong datatype and associated DFDL latlong properties ..... If only we could extend DFDL ....... How about making DFDL extensible? How about allowing users of DFDL to create their own datatypes (actually, XSD already allows this) and allow users to create their own DFDL properties for the user-defined datatype? That is, how about turning DFDL into extensible DFDL? Thoughts? /Roger
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