Because the branch under one detection of a feature must be the same as the branch under any other feature, the tree structure is equivalent to a rooted acyclic graph: just instead of having graph links the branches get replicated.

The cost is potential for an explosion due to replication, but if you do need to make a list of all the causes of a particular feature F, the XPath is simple (//*[F]) and perhaps a niche requirement. 

I would expect the number of feature of interest would be way smaller than the size of the document: (if there is no clustering and the number of alternative features gets closer to the number of possible element, you are left with a kind of trimmed instance not really feature extraction.)

Rick

On Sun, Oct 9, 2016 at 3:45 AM, Dimitre Novatchev <dnovatchev@g...> wrote:

On Sat, Oct 8, 2016 at 2:16 AM, Rick Jelliffe <rjelliffe@a...> wrote:
> * It allows grammar-like modeling of the hierarchical feature set
> combinations in the document, and the reporting as a feature tree ...

Isn't the feature dependency best modelled as a graph?


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Cheers,
Dimitre Novatchev
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