Introduction to UNL

Revision as of 18:06, 16 April 2009

The Universal Networking Language (UNL) is an artificial language for representing, describing, summarizing, refining, storing and disseminating information in a machine- and natural-language-independent form. It is a kind of mark-up language which represents not the formatting but the core information of a text. As HTML annotations can be realized differently in the context of different applications, machines, displays, etc., so UNL expressions can have different realizations in different human languages. The UNL was born within the United Nations and was conceived at the Institute of the Advanced Studies of the United Nations University. It is the property of the United Nations and, therefore, an asset of all of humankind.

History

The UNL Programme started in 1996, as an initiative of the Institute of Advanced Studies of the United Nations University in Tokyo, Japan. In January 2001, the United Nations University set up an autonomous organization, the UNDL Foundation, to be responsible for the development and management of the UNL Programme. The Foundation, a non-profit international organisation, has an independent identity from the United Nations University, although it has special links with the UN. It inherited from the UNU/IAS the mandate of implementing the UNL Programme so that it can fulfil its mission. Its headquarters are based in Geneva, Switzerland.

From the very beginning, a consortium of university departments from all regions of the world has been engaged in developing the UNL. That's the UNL Society, a global-scale network of R&D teams, involving about 200 specialists in computer science and linguistics, who are at work creating the linguistic resources and developing the web structure of the UNL System. The UNL Centre provides technological support and co-ordinates the implementation of the Programme.

The Programme has already crossed important milestones. The overall architecture of the UNL System has been developed with a set of basic software and tools necessary for its functioning. These are being tested and improved. A vast amount of linguistic resources from the various native languages already under development, as well as from the UNL expression, has been accumulated in the last few years. Moreover, the technical infrastructure for expanding these resources is already in place, thus facilitating the participation of many more languages in the UNL system from now on. A growing number of scientific papers and academic dissertations on the UNL are being published every year.

The most visible accomplishment so far is the recognition by the Patent Co-operation Treaty (PCT) of the innovative character and industrial applicability of the UNL, which was obtained in May 2002 through the World Intellectual Property Organisation (WIPO). Acquiring the patent for the UNL is a completely novel achievement within the United Nations.

Scope and Goals

The UNL is an effort to achieve a simple basis for representing the most central aspects of information and meaning in a machine- and human-language-independent form. As a language-independent formalism, the UNL aims at coding, storing, disseminating and retrieving information independently of the original language in which it was expressed. In this sense, UNL seeks to provide the tools for overcoming the language barrier in a systematic way.

At first glance, the UNL seems to be a multilingual machine translation system, i.e., a kind of Interlingua, to which the source texts are converted before being translated into the target languages. It can, in fact, be used for such a purpose, and very efficiently too. However, its real strength is to represent knowledge and its primary objective is to serve as an infrastructure for handling knowledge that already exists or can exist in any given language.

Nevertheless, it is important to note that at this point in time it would be foolish to state it possible to represent the “full” meaning of any word, sentence or text for any language. Subtleties of intention and interpretation make the “full meaning”, whatever concept we might have of it, too variable and subjective for any systematic treatment. The UNL avoids the pitfalls of trying to represent the “full meaning” of sentences or texts, targeting instead the “core” or “consensual” meaning that is most often attributed to them. In this sense, much of the subtlety of poetry, metaphor, figurative language, inuendo and other complex, indirect communicative behaviors is beyond the current scope and goals of the UNL. Instead, the UNL targets direct communicative behavior and literal meanings as a tangible, concrete basis for much or most of human communication in practical, day-to-day settings.

Structure

In the UNL approach, information conveyed by natural language is represented, sentence by sentence, as a hypergraph composed of a set of directed binary labeled links (referred to as “relations”) between nodes or hypernodes (the “Universal Words”, or simply “UW”), which stand for concepts. UWs can also be annotated with “attributes" representing context information..

As a matter of example, the English sentence ‘The sky was blue?!’ can be represented in UNL as follows:

In the example above, "sky(icl>natural world)" and "blue(icl>color)", which represent individual concepts, are UWs; "aoj" (= attribute of an object) is a directed binary semantic relation linking the two UWs; and "@def", "@interrogative", "@past", "@exclamation" and "@entry" are attributes modifying UWs.

UWs are supposed to represent universal concepts and are expressed in English words in order to be humanly-readable. They consist of "headword" (the UW root) and a "constraint list" (the UW suffix between parentheses), the latter being used to disambiguate the general concept conveyed by the former. The set of UWs, which is currently around 63,000 entries, is organized in an ontology-like structure (the so-called "UW System"), where upper concepts are used to disambiguate the lower ones through "icl" (= is a kind of) and "iof" (= is an instance of) relations.

Relations are expected to represent semantic links between words in every existing language. They can be ontological (such as "icl" and "iof" referred to above), logical (such as "and" and "or") and thematic (such as "agt" = agent, "ins" = instrument, "tim" = time, "plc" = place, etc). There are currently 46 relations in the UNL Specs, and they define the syntax of UNL.

Attributes represent information that cannot be conveyed by UWs and relations. Normally, they represent information on tense (".@past", "@future", etc), reference ("@def", "@indef", etc), modality ("@can", "@must", etc), focus ("@topic", "@focus", etc), .and so on.

Under the UNL Program, the process of representing natural language sentences in UNL graphs is called "enconverting", and the process of generating natural language sentences out of UNL graphs is called "deconverting". The former, which involves natural language analysis and understanding, is supposed to be carried out semi-automatically (i.e., in a computer-aided human basis); the latter is expected to be done fully-automatically.