computer science

Temporal expressions

Temporal expressions is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Temporal expressions rather than just read about it. In short: A temporal expression in a text is a sequence of tokens (words, numbers and characters) that denote time, that is express a point in time, a duration or a frequency. Examples: A point in time: He was born on <TIMEX>6 May, 1980</TIMEX>.

Key takeaways

Temporal expressions belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Temporal expressions to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Temporal expressions from memory before moving on to harder problems.

Reference excerpt

A temporal expression in a text is a sequence of tokens (words, numbers and characters) that denote time, that is express a point in time, a duration or a frequency. Examples:

A point in time: He was born on <TIMEX>6 May, 1980</TIMEX>. A duration: The show lasted <TIMEX>7 minutes</TIMEX>. A frequency: The pump circulates the water <TIMEX>every 2 hours</TIMEX>. Initially, temporal expressions were considered a type of named entities and their identification was part of the named entity recognition task. Since the Automatic Content Extraction program in 2004 there has been a separate task identified and called Temporal Expression Recognition and Normalisation (TERN). Timex evaluation is now evaluated in two major temporal annotation challenges: TempEval and i2b2, both of which prefer the TimeML-level TIMEX3 standard.

Approaches Similarly to NER systems, temporal expression taggers have been created either using linguistic grammar-based techniques or statistical models. Hand-crafted grammar-based systems typically obtained better results, but at the cost of months of work by experienced linguists. There are many such systems available now, so creating a temporal expression recognizer from scratch is generally an undesirable duplication of effort. Instead, current approaches focus on novel subclasses of timex. Statistical systems typically require a large amount of manually annotated training data and are usually applied to the recognition task only (although there is work done using machine learning algorithms to resolve certain ambiguities in the interpretation step).

Notes

References Ahn, David; van Rantwijk, Joris; de Rijke, Maarten (2007), "A Cascaded Machine Learning Approach to Interpreting Temporal Expressions" (PDF), Proceedings of Human Language Technologies: The Annual Conference of the North American Chapter of the Association for Computational Linguistics (NAACL-HLT 2007), ACL Filannino, Michele; Brown, Gavin; Nenadic, Goran (2013), "ManTIME: Temporal identification and normalization in the TempEval-3 challenge" (PDF), Proceedings of the 7th International Workshop on Semantic Evaluation, ACL

Worked examples

Example 1 — a first encounter with Temporal expressions

Start with the simplest possible case. Write down what Temporal expressions claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Temporal expressions before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Temporal expressions ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Temporal expressions

In research: Temporal expressions appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Temporal expressions in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Temporal expressions is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computational linguistics, Data modeling languages, Time, so understanding it makes those chapters shorter.
In everyday life: Look for Temporal expressions outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Temporal expressions in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Temporal expressions means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Temporal expressions out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Temporal expressions in simple terms?

A temporal expression in a text is a sequence of tokens (words, numbers and characters) that denote time, that is express a point in time, a duration or a frequency. Examples: A point in time: He was born on <TIMEX>6 May, 1980</TIMEX>.

Why does Temporal expressions matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Temporal expressions?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Temporal expressions.