HTML Alternatives for Non-W3C Technologies
WAI Definition (Checkpoint 11.1)
Use W3C technologies when they are available and appropriate for a task and use the latest versions when supported.
Publish web content in HTML format. If you publish web content using another format, then you should provide an alternative HTML version. This applies in particular to Flash and PDF formats.
The official UN document hosted on the ODS are an exception to this rule. It is allowed to link to those documents without re-creating an HTML version, even though the official document will not be in an accessible format.
Creating accessible documents in PDF or Flash formats raises a number of different accessibility issues. At this point, the W3C has not yet issued accessibility guidelines for these types of formats.
Check the site for non-HTML elements.
If content is published in a non-HTML format, such as Flash or PDF, an accessible, up-to-date HTML format version should be provided.
Does not apply to ODS documents.