Use BITS book-part element for parts and chapters.

[davidmjones]

Currently we use <sec> for parts and chapters, but the <book-part> element is more appropriate.

[pkra]

Downstream issue: AmerMathSoc/texml-to-html#495

[pkra]

@davidmjones do you have a current example code for review to get started with the downstream adjustments?

From the initial examples, the only detail I've found missing is specific-use.

[davidmjones]

@pkra I think I've finally gotten this right. See book-new.xml in the tests directory and the comments at the bottom of lib/perl/TeX/Interpreter/LaTeX/Class/BITS.xml.

[pkra]

Thanks, @dmj. First observations based on book-new.xml:

• for \part, specific-use is chapter, both on toc-entry and book-part. I think it should be part.
• \chapter after \part no longer creates nested markup (neither in the toc nor in the body).
  • Is there a reason for this change? (It will break other things downstream.)
• what should happen if the main matter starts with chapters before parts? (IIRC we have a use case.)

If I insert \chapter{Hello World} between \mainmatter and \part{First Part} (in new-book.tex), I get:

<toc-entry specific-use="chapter">
   <label>Chapter 2<x>.</x></label>
   <title>First part</title>
   <nav-pointer rid="ltxid9"/>
</toc-entry>

and

<title-group>
   <label>Part 2</label>
   <title>First part</title>
</title-group>

More of an aside: foreword is a new element and thus unsupported downstream. It's easy enough to support downstream later on.

[davidmjones]

@pkra: That's what I get for adding parts to the test file at the last minute. Try now.

[pkra]

Thanks, @davidmjones. It looks much improved. It also seems to fix #223 which is nice. (Apropos nothing, it's odd that BITS doesn't allow title-group in sec - or at least in sec-meta.)

Adjusting texml-to-html seems straight forward.

I'll start testing things further downstream.

[pkra]

Some more notes from more testing.

• There's a disp-level drop in the test file - part "First part" has level 1, nested "First Chapter title" has level 3, nested section "Introduction" has level 5. (I don't think disp-level is used downstream anymore though.)
• I don't think we've had specific-use="appendix" before; texml-to-html will need a small adjustment.

[pkra]

Oh, and the various frontmatter parts now mostly have specific-use="chapter". Not sure if that was intentional; downstream is ok either way.

[davidmjones]

The specific-use for the frontmatter parts reflects the fact that they all correspond to \chapter in the LaTeX file. The same is true of <book-app/>, but the different specific-use there is loosely related to the fact that cleverref needs to know the difference in order to generate the correct labels for references. I could disentangle those two uses, but since it's easy to support downstream, let's use it.

[pkra]

FWIW I think it's an improvement having specific-use in frontmatter and having appendix value for the appendix. They provide insight into the source in a useful way, I think.