Annotation guidelines for main event annotation

Amber Stubbs, SeoHyun Im, Roser Saurí, Marc Verhagen

Version 2, December 2006.


Basic definitions

We consider main events within the scope of a sentence. With that in mind, we start by defining the basic notions at play: sentence, and event.

Sentence

We adopt the notion of sentence standardly assume in the NLP community. That is, as the basic textual unit immediately above the phrase which ends with a terminal punctuation mark, such as: ., ?, or !. Example (1) contains two different sentences (delimited by the <s> tag), whereas example (2) has only one.

(1) <s>Australia has been independent since 1901.</s> <s>However, it still recognizes the British monarch as its head of state.</s>

(2) <s>Australia has been independent since 1901, but it still recognizes the British monarch as its head of state.</s>

Event

Event is a cover term for predicates describing:

Events can be denoted by verbs (reach, evacuate), adjectives (available, outstanding), or nouns (search, payment).

Events in text are annotated following TimeML annotation guidelines (Saurí et al., 2005:section 2.1.1). These guidelines cover problematic cases in detail, such as: light verb constructions, complex verb forms (with auxiliaries and/or polarity particles), phrasal verbs, predicative constructions, etc.

Identifying main events

There will be only one main event per sentence.

Identifying the main event in a sentence that has only one event is trivial, since this automatically becomes the main event of that sentence.

In the case of sentences with multiple events (e.g., example 5), the main event will be determined following very shallow, syntactic-based criteria.

(5) ``We're expecting a major eruption,'' he said in a telephone interview early today.

Two different situations can be distinguished here:

Subordination contexts

The main event will be the event that is dominant syntactically. This apply to all kinds of subordination. Here, we list the most relevant for reference.

  1. that-clauses: They are introduced by the conjunction that, although in some cases this can be omitted. Grammatically, they can function in different roles, such as subject (6) or object (7) of certain verbs. In the following examples, the two relevant events are in bold face, with the main one underlined.

    (6) It surprised me [that Gulshan Lake has so many little bugs and bacteria].

    (7) He told reporters [(that) he had no message from Baghdad].

  2. if- and wh-clauses: Introduced by the cojunctions if and whether (8), or by a wh particle (who, where, what, how, etc.) (9). Grammatically, they can function as object or subject of a verb as well.

    (8) Reporters asked President Bush [whether the interdiction would apply to food].

    (9) The panel is investigating [who shot down Rwandan President Juvenal Habyarimana's plane on April 6, 1994].

  3. Relative clauses: They are noun modifiers. In case that the noun head denotes an event and is not subordinated to any other event in the sentence, this noun will be the main event.

    (10) A war [that is supposed to help feed the desperate people of Afghanistan].

  4. Small clauses: They are minimal predicate structures with no tense. We are also including here ing-clauses (13).

    (11) Several neighbors heard [it happen].

    (12) Her wife convinced [him to leave the country].

    (13) I don't see things [getting as acrimonious as they do].

  5. Adverbial clauses: Introduced by subordinating conjunctions expressing: temporal relations (after, before, when, while), purpose (to, in order to, so that), cause (because, since), condition (if, unless), or contrast (although, even though, while), comparison (similar to, like). Note that none of these lists are necessarily exhaustive.

    (14) He stayed behind because he couldn't speak French.

    (15) So when Wong Kwan spent seventy million dollars for this house, he thought it was a great deal.

  6. Comparative clauses: The subordinated clause is introduced by conjunctions as or than.

    (16) There have been far more participants this year [than there were last year].

    (17) He is about as old [as his father was at his age].

    Two comments need to be made here. First, note that the main events selected here (participants, old) do not denote an event by themselves. They are however annotated as events following the TimeML annotation guidelines (Saurí et al, 2005), which specify that the copular verb be is never marked as event, but the head of their predicative complement instead.

    Second, in (17) there are two phrases introduced by the conjunction as. The subordinated phrase is the second one.

  7. NPs, APs, or PPs headed by an event-denoting element: They can function as subjects, objects, or other arguments of verbal predicates (18-19). They can also be complements of nouns (20) or adjectives (21).

    (18)[The transaction] has been approved by Kyle's board.

    (19) The new Essex County task force is delving [into the slayings of 14 black women].

    (20) There was no independent confirmation [of the fact] by the government-run news agency.

    (21) The agreement is subject [to shareholder and regulatory approval].

Controversial cases

Coordination contexts

The main event will be the first one of the two coordinated events. Some coordinating conjunctions in English are: and, or, but, nor, yet, so, as well as, only, such that.

(26) He sold the property to five buyers [and] said he'd double his money.

(27) Australia has been independent since 1901, [but] like many Commonwealth nations it still recognizes the British monarch as its head of state.

(28) I had hoped to see her, [only] she did not come.

(29) The work started very hard, [such that] many people were injured.

Guidelines basic scheme

  1. Annotate only one main event per sentence.
  2. In subordination relations, the main event is the dominant syntactically.
  3. In coordination relations, the main event is the first one in the sentence string.

References

Saurí, R., J. Littman, B. Knippen, R. Gaizauskas, A. Setzer, J. Pustejovsky. 2005. TimeML Annotation Guidelines. http://www.timeml.org.