# Source\_sink dtd does not exist

**URL:** <https://swi-prolog.discourse.group/t/source-sink-dtd-does-not-exist/8734>\
**Category:** Help!\
**Created:** [January 17, 2025, 9:01am UTC](https://swi-prolog.discourse.group/t/source-sink-dtd-does-not-exist/8734 "2025-01-17T09:01:48Z")\
**Posts on this page:** 1\
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**Author:** ![kwon-young](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/kwon-young/32/4841_2.png) [@kwon-young](https://swi-prolog.discourse.group/u/kwon-young)\
**Post date:** [January 17, 2025, 12:36pm UTC](https://swi-prolog.discourse.group/t/source-sink-dtd-does-not-exist/8734/3 "2025-01-17T12:36:24Z")

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Hello,  
I also tried to use xml schemas for MusicXML or MEI in the past but could not understand a thing from the swi-prolog documentation.  
In my case, I wanted to do automatic conversion of numbers from atom to prolog numbers when reading and writing xml, but I don’t think this is implemented at all.

Just for curiosity, could you tell us what kind of project are you using MusicXML and prolog for ?  
In my case, I’m trying to write a [pure bidirectional grammar of the common music notation](https://swi-prolog.discourse.group/t/music-notation-grammar/5729/6).

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