IN 1867, THE RUSSIAN EMPIRE SOLD THE ALASKAANTECEDENTS DESCRIBING T...

3. In 1867, the Russian Empire sold the Alaska

antecedents describing the syntax of the question.

territory to the USA.

Input: (a) Query: “When was Alaska purchased?”(b) Answer sentence: “The acquisition of Alaska happened in 1867.”Step 1: Question is segmented into key phrases and stop words:

When[1]+was[2]+NP[3]+VERB[4]

Step 2: Key question phrases are aligned with key answer sentence phrases:

[3]Alaska

→

Alaska

[4]purchased

→

acquisition

ANSWER

→

1867

Step 3: A pre-computed parse tree of the answer sentence is loaded: