is Guide useful in OPF 3.0 given that NCX support is now a "MUST"

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It was previously decided that EPUB3 should change "Reading Systems SHOULD 
support NCX" to "Reading Systems MUST support NCX". Implications of this change 
relative to Guide are not clear to me.

In particular, I cannot find words to express why one might want to author 
Guide as well as NCX in EPUB3 since both seem to express the notion of a 
declarative Table of Contents. If there is no logical reason, other than 
backwards compatibility of Reading Systems with old content and of EPUB3 
content that can work with old Reading Systems, then
we should consider removing from content conformance (leaving support for Guide 
as a Reading System conformance) or at least deprecating (clarifying that we 
view it as a vestigial construct there due to history). If we don't 
remove/deprecate we need to find a way to express why one might want to create 
a Guide that is not backwards-looking.

We believe EPUB content exists that includes "Guide". It is not clear to me 
whether such content always includes an "NCX" nor how they relate to each other.

Spec details:

In OPF 2.0.1 Guide is defined as "A set of references to fundamental structural 
features of the publication, such as table of contents, foreword, bibliography, 
etc." NCX is defined as "A declarative global navigation definition". authors 
MUST include NCX and MAY include Guide, Reading Systems SHOULD support NCX 
(silent about, so presumably MAY support Guide).

Original issue reported on code.google.com by whmc...@gmail.com on 26 Oct 2010 at 4:45

[GoogleCodeExporter]

decision - deprecate

Original comment by whmc...@gmail.com on 10 Nov 2010 at 1:21

• Changed state: Answered