Hi Richard,
It is good to hear from you. We are still plugging away, and you are
correct, we are just finishing our work on importing GrAF (Graph
Annotation Framework) models into UIMA. I just wanted to do a quick
sanity check incase I was missing anything obvious.
At 01:23 AM 5/8/2009, Richard Eckart wrote:
The type systems I do it in the same manner you do, only they may use
just a "children" or just a "parents" feature and assume that an edge
is always directed from parent to child - thus having both would be
redundant.
Redundant yes, but having both allows easy navigation in both
directions given a particular annotation. It is the classic space vs
speed tradeoff and we do a lot of things like: find the target of a
given FrameNet annotation and then determine what part of the syntax
tree it belongs to.
Actually the CAS is a DAG. You have an edge whenever a feature
structure references another feature structure.
Yes, I should have phrased my question more carefully. I was
wondering about more explicit representations. For example, I see
there is an AnnotationTreeNode interface and was hoping for a similar
GraphNode interface.
I like your idea of expressing edges with an explicit 'Edge' feature
structure as edges are already feature structures in GrAF and this
provides a nice one-to-one correspondence. However, it would likely
make sense to allow the user to specify if edges should be implicit
(a reference to an annotation feature structure) or explicit (a
reference to an Edge feature structure). While GrAF allows labelled
edges, we don't actually have any graphs that label edges right now
so adding the extra layer of indirection would simply be extra
overhead, particularly for graphs with thousands of edges.
I am pretty sure this is already more or less how you handle things,
so in reiterating it I am probably only expressing that I do not know
of any better idea either.
It sounds like we are on the same page. Thanks for the feedback.
Cheers,
Keith
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Research Associate
American National Corpus
http://www.anc.org
