Interpretation of bare weekday names

Many temporal expressions in text are underspecified, requiring contextually-sourced information in order to determine their correct interpretation. In some cases, it is sufficient to determine what is sometimes called the temporal focus, so that the precise location of a relative temporal expression
on a timeline can be determined with respect to this ‘time of speaking’. Consider, for example, expressions like the following:
(1) three days ago
(2) last Monday
(3) in two weeks time
Once we know the temporal focus, calculation of the temporal location referred to in each of these cases is straightforward, since the temporal expressions themselves explicitly indicate what we will call the direction of offset (here, respectively, past, past and future). However, in other cases there is no explicit indication of the direction of offset from the temporal focus. This is most obviously the case when bare expressions based on calendar cycles—i.e., weekday names and month names—are used, as in the following example:

(4) Jones met with Defense Minister Paulo Portas on Tuesday and will meet Foreign Minister Antonio Martins da Cruz before leaving Portugal Wednesday.

Here, the proper interpretation of the references to Tuesday and Wednesday requires at the least a correct syntactic analysis of the sentence, in order to locate the controlling verb for each weekday name. The tense of this verb can then be used to determine the direction—either in the past or in the future—in which we need to look to establish the fully specified date referred to. In the case of example (4), this means determining that Tuesday is in the scope of the verb met, and that Wednesday is in the scope of the verb group will meet.

It turns out that there are cases where even the controlling verb does not provide sufficient information to determine the direction of offset. But even in those cases where the tense of the verb does provide the relevant information, there are two problems. First, especially when the sentences considered are complex, there is a non-negligible likelihood that the analysis returned by a parser may not be correct, and this is especially the case when the sentences in question contain structures such as prepositional phrases: the attachment of these is notoriously a source of ambiguity, and they just happen to often be the hosts to temporal expressions. Second, even if a parser provides the correct analysis, parsing technology is still computationally expensive to use when processing very large bodies of text; if we are interested in time-stamping events described in significant volumes of data, we would prefer to have a faster, more heuristic-based approach.

Research results published in this topic:

  • Mazur and Dale (2008)

P Mazur, R Dale [2008] What's the Date? High Accuracy Interpretation of Weekday Names,
In the Proceedings of the 22nd International Conference on Computational Linguistics (Coling),
16-24 August, Manchester, UK, pages 553-560.
PDF: http://web.science.mq.edu.au/~mpawel/publications.php

Abstract:
In this paper we present a study on the interpretation of weekday names in texts. Our algorithm for assigning a date to a weekday name achieves 95.91% accuracy on a test data set based on the ACE 2005 Training Corpus, outperforming previously reported techniques run against this same data. We also provide the first detailed comparison of various approaches to the problem using this test data set, employing re-implementations of key techniques from the literature and a range of additional heuristic-based approaches.

Data:
To obtain the data set used in the experiments please contact one of the authors:
Pawel Mazur (pawel.mazur at mq.edu.au), or
Robert Dale (robert.dale at mq.edu.au)
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IMPORTANT:  You should only use this data if you have a licence for the full
ACE 2005 Multilingual Training Corpus offered by the Linguistic Data
Consortium (LDC) under the catalogue number LDC2006T0.
http://www.ldc.upenn.edu/Catalog/CatalogEntry.jsp?catalogId=LDC2006T06
Please contact LDC for information how to acquire the licence.
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