GutenLink - Adding TLINK Tags

Georgetown's GUTenLINK TLINK tagger uses hand-developed syntactic and lexical rules. It handles three different cases at present: (i) the event is anchored without a signal to a time expression within the same clause, (ii) the event is anchored without a signal to the document date speech time frame (as in the case of reporting verbs in news, which are often at or offset slightly from the speech time), and (iii) the event in a main clause is anchored with a signal or tense/aspect cue to the event in the main clause of the previous sentence. In case (iii), a finite state transducer is used to infer the likely temporal relation between the events based on TimeML tense and aspect features of each event. For example, a past tense non-stative verb followed by a past perfect non-stative verb, with grammatical aspect maintained, suggests that the second event precedes the first.

GUTenLINK uses default rules for ordering events; its handling of successive past tense non-stative verbs in case (iii) will not correctly order sequences like Max fell. John pushed him. GUTenLINK is intended as one component in a larger machine-learning based framework for ordering events. Another component which will be developed will leverage document-level inference, as in the machine learning approach of Mani et al (2003), which required annotation of a reference time (Reichenbach 1947, Kamp and Reyle 1993) for the event in each finite clause.

An early version of GUTenLINK was scored at .75 precision on 10 documents. More formal Precision and Recall scoring is underway, but it compares favorably with an earlier approach developed at Georgetown. That approach converted event-event TLINKs from TimeBank 1.0 into feature vectors where the TLINK relation type was used as the class label (some classes were collapsed). A C5.0 decision rule learner trained on that data obtained an accuracy of .54 F-measure, with the low score being due mainly to data sparseness.

An example of GUTenLINK output is shown below, the added TLINKs are in bold type.

In Washington <TIMEX3 tid="t1" TYPE="DATE" VAL="PRESENT_REF" temporalFunction="true" valueFromFunction="tf1" anchorTimeID="t0">today</TIMEX3>, the Federal Aviation Administration <EVENT eid="e1" class="OCCURRENCE">released</EVENT> air traffic control tapes from the night the TWA Flight eight hundred <EVENT eid="e2" class="OCCURRENCE">went</EVENT> down. There's nothing new on why the plane <EVENT eid="e3" class="OCCURRENCE">exploded</EVENT>, but you <EVENT eid="e4" class="OCCURRENCE">cannot</EVENT> <EVENT eid="e5" class="OCCURRENCE">miss</EVENT> the moment. ABC's Lisa Stark <EVENT eid="e6" class="OCCURRENCE">has</EVENT> more.

References

Hans Kamp and Uwe Reyle. 1993. From Discourse to Logic. Tense and Aspect. Pages 483--546. Kluwer Academic Publishers, Dordrecht, Netherlands.

Inderjeet Mani, Barry Schiffman and Jianping Zhang. 2003. Inferring Temporal Ordering of Events in News. Proceedings of the Human Language Technology Conference (HLT-NAACL'03). Short Paper.

Hans Reichenbach. 1947. Elements of Symbolic Logic. MacMillan, London.