| Local Name | Namespace URI | Description |
| get-tts-annotations | http://www.daisy.org/ns/pipeline/xproc | |
| isolate-skippable | http://www.daisy.org/ns/pipeline/xproc | Break up sentences into sub-sentences that do not contain skippable elements. |
| ssml-to-audio | http://www.daisy.org/ns/pipeline/xproc | |
| text-to-ssml | http://www.daisy.org/ns/pipeline/xproc | Generate the TTS input, as SSML snippets. |