WordNet
WordNet is a semantic lexicon for the English language that computational linguists and cognitive scientists use extensively. For example, WordNet was a key component in IBM’s Jeopardy-playing Watson computer system. WordNet groups words into sets of synonyms called synsets. For example, { AND circuit, AND gate } is a synset that represent a logical gate that fires only when all of its inputs fire. WordNet also describes semantic relationships between synsets. One such relationship is the is-a relationship, which connects a hyponym (more specific synset) to a hypernym (more general synset). For example, the synset { gate, logic gate } is a hypernym of { AND circuit, AND gate } because an AND gate is a kind of logic gate.
The WordNet digraph. Your first task is to build the WordNet digraph: each vertex v is an integer that represents a synset, and each directed edge v→w represents that w is a hypernym of v. The WordNet digraph is a rooted DAG: it is acyclic and has one vertex—the root—that is an ancestor of every other vertex. However, it is not necessarily a tree because a synset can have more than one hypernym. A small subgraph of the WordNet digraph appears below.
The WordNet input file formats. We now describe the two data files that you will use to create the WordNet digraph. The files are in comma-separated values (CSV) format: each line contains a sequence of fields, separated by commas.
AND_circuit, AND_gate }
has an id number of 36 and its gloss is
a circuit in a computer that fires only when all of its inputs fire.
The individual nouns that constitute a synset are separated by spaces.
If a noun contains more than one word, the underscore character connects
the words (and not the space character).
AND_circuit AND_Gate)
has 42338 (gate logic_gate) as its only hypernym. Line 34 means that
synset 34 (AIDS acquired_immune_deficiency_syndrome) has two hypernyms:
47569 (immunodeficiency) and 48084 (infectious_disease).
WordNet data type.
Implement an immutable data type WordNet with the following API:
public class WordNet {
// constructor takes the name of the two input files
public WordNet(String synsets, String hypernyms)
// returns all WordNet nouns
public Iterable<String> nouns()
// is the word a WordNet noun?
public boolean isNoun(String word)
// distance between nounA and nounB (defined below)
public int distance(String nounA, String nounB)
// a synset (second field of synsets.txt) that is the common ancestor of nounA and nounB
// in a shortest ancestral path (defined below)
public String sap(String nounA, String nounB)
// do unit testing of this class
public static void main(String[] args)
}
Corner cases.
Throw an IllegalArgumentException in the following situations:
null
distance() or sap()
is not a WordNet noun.
Performance requirements.
Your data type should use space linear in the input size
(size of synsets and hypernyms files).
The constructor should take time linearithmic (or better) in the input size.
The method isNoun() should run in time logarithmic (or better) in
the number of nouns.
The methods distance() and sap() should run in time linear in the
size of the WordNet digraph.
For the analysis, assume that the number of nouns per synset
is bounded by a constant.
Shortest ancestral path. An ancestral path between two vertices v and w in a digraph is a directed path from v to a common ancestor x, together with a directed path from w to the same ancestor x. A shortest ancestral path is an ancestral path of minimum total length. We refer to the common ancestor in a shortest ancestral path as a shortest common ancestor. Note also that an ancestral path is a path, but not a directed path.
We generalize the notion of shortest common ancestor to subsets of vertices. A shortest ancestral path of two subsets of vertices A and B is a shortest ancestral path over all pairs of vertices v and w, with v in A and w in B. The figure (digraph25.txt) below shows an example in which, for two subsets, red and blue, we have computed several (but not all) ancestral paths, including the shortest one.
SAP data type.
Implement an immutable data type SAP with the following API:
public class SAP {
// constructor takes a digraph (not necessarily a DAG)
public SAP(Digraph G)
// length of shortest ancestral path between v and w; -1 if no such path
public int length(int v, int w)
// a common ancestor of v and w that participates in a shortest ancestral path; -1 if no such path
public int ancestor(int v, int w)
// length of shortest ancestral path between any vertex in v and any vertex in w; -1 if no such path
public int length(Iterable<Integer> v, Iterable<Integer> w)
// a common ancestor that participates in shortest ancestral path; -1 if no such path
public int ancestor(Iterable<Integer> v, Iterable<Integer> w)
// do unit testing of this class
public static void main(String[] args)
}
Corner cases.
Throw an IllegalArgumentException in the following situations:
null
null item
Performance requirements. All methods (and the constructor) should take time at most proportional to E + V in the worst case, where E and V are the number of edges and vertices in the digraph, respectively. Your data type should use space proportional to E + V.
Test client. The following test client takes the name of a digraph input file as as a command-line argument, constructs the digraph, reads in vertex pairs from standard input, and prints out the length of the shortest ancestral path between the two vertices and a common ancestor that participates in that path:
public static void main(String[] args) {
In in = new In(args[0]);
Digraph G = new Digraph(in);
SAP sap = new SAP(G);
while (!StdIn.isEmpty()) {
int v = StdIn.readInt();
int w = StdIn.readInt();
int length = sap.length(v, w);
int ancestor = sap.ancestor(v, w);
StdOut.printf("length = %d, ancestor = %d\n", length, ancestor);
}
}
