Chinese Word Breaking

[Richard Wordingham]

I'm puzzled by a statement in UAX #29 Unicode Text Segmentation:

"In particular, the characters with the Line_Break property values of
Contingent_Break (CB), Complex_Context (SA/Southeast Asian), and
Unknown (XX) are assigned word boundary property values based on
criteria outside of the scope of this annex. That means that
satisfactory treatment of languages like Chinese or Thai requires
special handling."

Is 'Contingent_Break (CB)' an error for 'Ideographic (ID)'?  That would
make sense for Chinese, for some applications needs to group ideographs
into words.

While I am on the topic, does anyone know of character level
mechanisms used to advise alogrithms of the word boundaries (or lack
of boundaries) in Chinese text? 

Richard.