DFDL does neither parsing nor unparsing ... do you agree?

["Costello, Roger L." <co...@mitre.org>]

Hi Folks,

In my slides on DFDL I say this:


  *   To recap, DFDL's biggest innovations are that it is:
     *   Comprehensive - a union of the capabilities of prior systems
     *   Standardized
     *   Able to perform unparsing

I believe the last sub-bullet is incorrect. DFDL is a language. DFDL does neither parsing nor unparsing. A DFDL processor, using a description found in a DFDL schema, is able to do parsing and unparsing. Do you agree?

/Roger

Re: DFDL does neither parsing nor unparsing ... do you agree?

["Beckerle, Mike" <mb...@tresys.com>]

Well, the DFDL language *enables* unparsing.

The DFDL language doesn't "do" anything. The English language doesn't "do" anything either. No language does. So we should talk about what the language enables.

Many prior generation format description languages do not have unparsing - the ones focused on intake of data into databases for example.
Though some do have it - those focused on message brokering.

Unparsing support in earlier generation systems is not that great. DFDL actually has some substantial innovation here with the ability to compute values of elements that forward reference and measure the representation length of other elements. This is actually one of the most challenging aspects of implementing DFDL and is why the unparser is in many respects more complex than the parser in Daffodil.

There are some uses of DFDL that will require only parsing. In fact unparsing is an optional feature in the DFDL spec. meaning one can create a compliant implementation that does only parsing if that's all you care about.

________________________________
From: Costello, Roger L. <co...@mitre.org>
Sent: Monday, December 23, 2019 9:45 AM
To: users@daffodil.apache.org <us...@daffodil.apache.org>
Subject: DFDL does neither parsing nor unparsing ... do you agree?


Hi Folks,



In my slides on DFDL I say this:



  *   To recap, DFDL’s biggest innovations are that it is:
     *   Comprehensive - a union of the capabilities of prior systems
     *   Standardized
     *   Able to perform unparsing



I believe the last sub-bullet is incorrect. DFDL is a language. DFDL does neither parsing nor unparsing. A DFDL processor, using a description found in a DFDL schema, is able to do parsing and unparsing. Do you agree?



/Roger

Re: DFDL does neither parsing nor unparsing ... do you agree?

["Sloane, Brandon" <bs...@tresys.com>]

Yes, following the language of the spec, the DFDL processor does the parser/unparsing.
________________________________
From: Costello, Roger L. <co...@mitre.org>
Sent: Monday, December 23, 2019 9:45 AM
To: users@daffodil.apache.org <us...@daffodil.apache.org>
Subject: DFDL does neither parsing nor unparsing ... do you agree?


Hi Folks,



In my slides on DFDL I say this:



  *   To recap, DFDL’s biggest innovations are that it is:
     *   Comprehensive - a union of the capabilities of prior systems
     *   Standardized
     *   Able to perform unparsing



I believe the last sub-bullet is incorrect. DFDL is a language. DFDL does neither parsing nor unparsing. A DFDL processor, using a description found in a DFDL schema, is able to do parsing and unparsing. Do you agree?



/Roger