I would defer the accessibilitySummary to @avneeshsingh and/or @clapierre. I agree on the description piece.

It makes sense to have multiple strings in different languages. We also need to ensure that it is in sync with schema.org definition.
When we worked with schema.org people in 2016, AccessModeSufficient was the only accessibility metadata that was identified for array representation.
So, just a caution, we are near CR, so the changes that we make should be in sync with schema.org.

Thanks @avneeshsingh, I was wondering about the same thing. B.t.w., description is also defined similarly.

However... I believe all properties can use several text values out of the box with schema.org, as long as the order is irrelevant. The json-ld context file for schema.org does not preclude that, and the google structure date testing tool does not complain either. I tried the following test:

<script type='application/ld+json'>
{
"@context":"http://schema.org",
"type":"CreativeWork",
"name": "somebody",
"description": ["one","two"],
"accessibilitySummary": ["this", "and that"]
}
</script>

and it worked without further ado. Ie, we may be o.k.

Right, this appears to be a case of our being more limiting than schema.org.

We've just thought of the summary in terms of a single language because most publications are not multilingual, but even in epub there's nothing to prevent you from adding it multiple times to the package document for different languages:

<meta property="schema:accessibilitySummary" xml:lang="en">...</meta>
<meta property="schema:accessibilitySummary" xml:lang="fr">...</meta>

The summary is the only field this applies to out of the accessibility metadata, just to be clear. The rest all expect predefined tokens (literals).

AccessModeSufficient is another unique case in that each individual entry is a list, but that's a different case than being able to represent strings in multiple languages.

This issue was discussed in a meeting.

• RESOLVED: the accessibilitySummary and description properties accept arrays of strings