how to create a sync-ToC in HTML

Sync-ToC is a feature of a lengthy document by means of which you can return from a section of a document to the element in the table of contents representing that section.  It is implemented by many help systems and very useful.  Is there a way to create such functionality within DocBook XSL?  It is similar but not identical to bread crumbs which are implemented and described; it is also supported "out of the box" in my x2html (which takes XHTML as input).  I noticed that the items in the ToC do not have identifiers in HTML output so asking how to figure out their identifiers is void as far as DocBook 4 is concerned.

This message is triggered by an enhancement request in XOrg [1].  However, since I find such functionality useful, I hope discussing it here will evoke broader interest to the problem.

Best regards,
Chris

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[1] <URL: https://bugs.freedesktop.org/show_bug.cgi?id=37362 >