But there’s unfortunately no simple guideline to give in terms of finding issues. It takes an eye for detail and an ear for possible different aural renderings. Editors and indexers are good starting resources for the process, as they should be able to quickly flag problem words during production so they don’t have to be rooted out after the fact. Programs that can analyze books and report on potentially problematic words, although not generally available, are not just a fantasy. Their prevalence will hopefully grow now that EPUB 3 incorporates more facilities to enhance default renderings, as they can greatly reduce the human burden.
The only other requirement when using the SSML attributes that I haven’t touched
on is that you always have to declare the SSML namespace. I’ve omitted the
declaration from the previous examples for clarity, and because the namespace is
typically only specified once on the root html
element as follows:
<html … xmlns:ssml="http://www.w3.org/2001/10/synthesis">
Similar to the alphabet attribute, we could have
equally well attached the namespace declaration to each instance where we used
the attributes:
<span
xmlns:ssml="http://www.w3.org/2001/10/synthesis"
ssml:ph="x-sampa"
…>
But that’s a verbose approach to markup, and generally only makes sense when content is encapsulated and shared across documents, as I just noted, or expected to be extracted into foreign playback environments where the full document context is unavailable.
The question you may still be wondering at this point is what happens if a PLS file contains a pronunciation rule that matches a word that is also defined by an SSML pronunciation, how can you be sure which one wins? You don’t have to worry, however, as the EPUB 3 specification defines a precedence rule that states that the SSML pronunciation must be honored. There’d be no way to override the global PLS definitions, otherwise, which would make SSML largely useless in resolving conflicts.
But to wrap up, a final note is that there is no reason why you couldn’t make all your improvements in SSML. It’s not the ideal way to tackle the problem, because of the text-level recognition and tagging it requires, at least in this author’s opinion, but it may make more sense to internal production to only use a single technology and/or support for PLS may not prove universal (it’s too early to know yet).