# ISO Prolog Part 3 (Definite clause grammar rules)
**URL:** https://swi-prolog.discourse.group/t/iso-prolog-part-3-definite-clause-grammar-rules/4348
**Category:** General
**Created:** [August 30, 2021, 1:32pm UTC](https://swi-prolog.discourse.group/t/iso-prolog-part-3-definite-clause-grammar-rules/4348 "2021-08-30T13:32:16Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@bagnara](https://swi-prolog.discourse.group/u/bagnara)
#### Post date: [August 30, 2021, 1:32pm UTC](https://swi-prolog.discourse.group/t/iso-prolog-part-3-definite-clause-grammar-rules/4348/1 "2021-08-30T13:32:16Z")
Hi there.
I am interested to know what readers of this list think about
> ISO/IEC NP TS 13211-3 NPOSA UNI/CT 524 2021-11-07
> Information technology
> Programming languages
> Part 3: Definite clause grammar rules
Please see attached draft.
Kind regards,
```
Roberto
```
(Attachment dcgsdraft-2021-08-16.pdf is missing)
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### Author:  [@EricGT](https://swi-prolog.discourse.group/u/EricGT)
#### Post date: [August 30, 2021, 1:44pm UTC](https://swi-prolog.discourse.group/t/iso-prolog-part-3-definite-clause-grammar-rules/4348/2 "2021-08-30T13:44:47Z")
> [@bagnara](#):
>
> (Attachment dcgsdraft-2021-08-16.pdf is missing)
The reason the PDF was not uploaded was because the site setting for authorized extensions that can be uploaded does not include `pdf`. Last I recall it was decided not to allow PDFs to be uploaded.
* * *
Here is a link for those interested:
> **[dcgsdraft-2021-08-16.pdf](https://www.complang.tuwien.ac.at/ulrich/iso-prolog/dcgs/dcgsdraft-2021-08-16.pdf)**
>
> 166.51 KB
* * *
For more historical information see the full directory from which the document comes.
[Index of /ulrich/iso-prolog/dcgs](https://www.complang.tuwien.ac.at/ulrich/iso-prolog/dcgs/)
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### Author:  [@jan](https://swi-prolog.discourse.group/u/jan)
#### Post date: [August 30, 2021, 2:29pm UTC](https://swi-prolog.discourse.group/t/iso-prolog-part-3-definite-clause-grammar-rules/4348/4 "2021-08-30T14:29:26Z")
> [@bagnara](#):
>
> I am interested to know what readers of this list think about
A quick read suggests it formalizes current practice. It is not easy to assess whether SWI-Prolog fully complies to all this. Would be nice if there are test cases that allow making this assessment. Overall, I’m in favor of complying unless there is a good reason not to.
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### Author:  [@EricGT](https://swi-prolog.discourse.group/u/EricGT)
#### Post date: [August 30, 2021, 2:37pm UTC](https://swi-prolog.discourse.group/t/iso-prolog-part-3-definite-clause-grammar-rules/4348/5 "2021-08-30T14:37:29Z")
> [@jan](#):
>
> Would be nice if there are test cases that allow making this assessment.
Writing the test cases for conformance seems easy enough (use code examples in the document) but I have little idea of how to test for nonconformance, any suggestions.
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### Author:  [@jan](https://swi-prolog.discourse.group/u/jan)
#### Post date: [August 30, 2021, 3:00pm UTC](https://swi-prolog.discourse.group/t/iso-prolog-part-3-definite-clause-grammar-rules/4348/6 "2021-08-30T15:00:26Z")
Having the examples as unit tests is nice to have. Note that [swipl-devel/test\_dcg.pl at 8c3b93b998d7e5fd318dd10c8b1cb7922f3c054c · SWI-Prolog/swipl-devel · GitHub](https://github.com/SWI-Prolog/swipl-devel/blob/8c3b93b998d7e5fd318dd10c8b1cb7922f3c054c/src/Tests/core/test_dcg.pl) is already written by Ulrich based on an older draft. Hopefully (and likely) not much changed.
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### Author:  [@EricGT](https://swi-prolog.discourse.group/u/EricGT)
#### Post date: [August 30, 2021, 6:47pm UTC](https://swi-prolog.discourse.group/t/iso-prolog-part-3-definite-clause-grammar-rules/4348/9 "2021-08-30T18:47:36Z")
> [@jan](#):
>
> Having the examples as unit tests is nice to have. Note that [swipl-devel/test\_dcg.pl at 8c3b93b998d7e5fd318dd10c8b1cb7922f3c054c · SWI-Prolog/swipl-devel · GitHub](https://github.com/SWI-Prolog/swipl-devel/blob/8c3b93b998d7e5fd318dd10c8b1cb7922f3c054c/src/Tests/core/test_dcg.pl) is already written by Ulrich based on an older draft.
Talked to Ulrich via e-mail and he noted about the document
> It is the first draft towards a TS.
So I don’t plan to do test cases for a draft but if it does reach a final document will take a look again. 😐
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### Author:  [@jan](https://swi-prolog.discourse.group/u/jan)
#### Post date: [August 30, 2021, 7:36pm UTC](https://swi-prolog.discourse.group/t/iso-prolog-part-3-definite-clause-grammar-rules/4348/11 "2021-08-30T19:36:54Z")
> [@EricGT](#):
>
> It is the first draft towards a TS.
Then there is no reason to hurry. DCGs have been on the ISO agenda since I joined the discussions, probably 20 years ago 🙂 We’ve seen various different approaches, none of which succeeded. I have the impression there is a fair compatibility among the current implementations. I might be wrong as I surely do no know all of them.