Each AMR is a single rooted, directed graph. AMRs include PropBank semantic roles, within-sentence coreference, named entities and types, modality, negation, questions, quantities, and so on. These two documents describe the AMR language:
As a simple example, we represent "The boy wants to go" as:
(w / want-01 :ARG0 (b / boy) :ARG1 (g / go-01 :ARG0 b))
Note that the variable b appears twice, once as the :ARG0 of want-01, and once as the :ARG0 of go-01. This same AMR can also be viewed as a feature structure graph:
We represent "About 14,000 people fled their homes at the weekend after a local tsunami warning was issued, the UN said on its Web site" as:
(s / say-01 :ARG0 (g / organization :name (n / name :op1 "UN")) :ARG1 (f / flee-01 :ARG0 (p / person :quant (a / about :op1 14000)) :ARG1 (h / home :poss p) :time (w / weekend) :time (a2 / after :op1 (w2 / warn-01 :ARG1 (t / tsunami) :location (l / local)))) :medium (s2 / site :poss g :mod (w3 / web)))
We have also developed disjunctive AMR, a packed representation for storing an exponential number of AMRs.