UNL2010

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The specifications here stated are still experimental and tentative, and have been continuously extended and amended in order to be as comprehensive as possible. They follow the general strategies defined in the [http://www.undl.org UNL 2005 Specifications] (version of June 7th, 2005), but introduce several important changes derived from different UNLization experiences. Although formally adopted in the UNDL Foundation tools, projects and certificates, they should not be taken yet as the official specs, as they are still under construction and have not been widely discussed with the UNL Community.  
 
The specifications here stated are still experimental and tentative, and have been continuously extended and amended in order to be as comprehensive as possible. They follow the general strategies defined in the [http://www.undl.org UNL 2005 Specifications] (version of June 7th, 2005), but introduce several important changes derived from different UNLization experiences. Although formally adopted in the UNDL Foundation tools, projects and certificates, they should not be taken yet as the official specs, as they are still under construction and have not been widely discussed with the UNL Community.  
  
== Background ==
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*[[Introduction to UNL]]
These specifications are derived from the four commitments of the UNL Programme (described at the [[Introduction to UNL]]):
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*[[Universal Words]]
 
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*[[Universal Attributes]]
I - The UNL must represent knowledge;
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*[[Universal Relations]]
II - The UNL must be language-independent
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*[[UNL sentence|UNL sentence structure]]
III - The UNL must be general-purpose
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*[[UNL document|UNL document structure]]
IV - The UNL must be machine-tractable
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They also comply with the 5 historical principles of the UNL:
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a) The UNL represents information through semantic networks
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b) The UNL includes a universal lexicon (the set of [[UW]]s)
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c) The UNL includes a set of semantic binary [[relations]]
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d) The UNL includes a set of semantic [[attributes]]
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e) The UNL is a markup language
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== THREE-LAYERED REPRESENTATION ==
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The basic assumption of the UNL approach is that the meaning conveyed by natural language can be formally represented through three different types of semantic units: UWs, attributes and relations. This three-layered representation model is the cornerstone of UNL and its most distinctive feature over other semantic networks, which normally propose only two levels: edges and vertices.
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[[Image:Unlgraph.jpg|center]]
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=== [[UW|UNIVERSAL WORDS (UWs)]] ===
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[[Image:Uw.jpg|left]]Universal Words, or simply UWs, are the words of UNL, and correspond to the nodes - to be interlinked by relations or modified by attributes - in a UNL graph. They are labels for relatively stable units of knowledge (the concepts) that can be associated to natural language '''open lexical categories (noun, verb, adjective and adverb)'''. The set of UWs is relatively open and is listed in the [[UNL Dictionary]]. Additionally, UWs are organized in a hierarchy (the [[UNL Ontology]]), are defined in the [[UNL Knowledge Base]] (UNL<sup>kb</sup>) and exemplified in the [[UNL Example Base]] (UNL<sup>eb</sup>), which are the lexical databases for UNL.
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The structure of UWs is presented in [[UW]]s.
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<br />
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=== [[Attributes|ATTRIBUTES]] ===
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[[Image:Attribute.jpg|left]]Attributes are arcs linking a node to itself. In opposition to relations, they correspond to one-place predicates, i.e., functions that take a single argument. In UNL, attributes are always preceded by "@" and have been normally used to represent information conveyed by '''bound morphemes and closed classes''', such as affixes (gender, number, tense, aspect, mood, voice, etc), determiners (articles and demonstratives), adpositions (prepositions, postpositions and circumpositions), conjunctions, auxiliary and quasi-auxiliary verbs (auxiliaries, modals, coverbs, preverbs) and degree adverbs (specifiers). They are also used to deal with non-verbal elements of communication, such as prosody, sentence and text structure, politeness, schemes, speech acts, etc.
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The current set of attributes is presented in [[Attributes]].
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=== [[Relations|RELATIONS]] ===
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[[Image:Relation.jpg|left]]Relations, formerly known as "links", are labelled arcs connecting a node to another node in a UNL graph. They correspond to two-place semantic predicates holding between two [[Universal Words]]. In UNL, relations have been normally used to represent semantic cases or thematic roles (such as agent, object, instrument, etc.) associated to the interpretation of '''syntactic relations''' (such as specification, complementation and adjunction). These functions are binary and directed (from a source to a target) and are claimed to be universal.
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Relations are organized in a hierarchy where lower nodes subsume upper nodes. The topmost level is the relation "rel", which simply indicates that there is a relation between two UWs. The following level brings four general relations: '''participant''' (ptp), for the necessary arguments (subject and complements) of verbal predicates; '''attribute''' (aoj), for the necessary arguments (subject and complement) of nominal predicates; '''specifier''' (mod), for general specifiers; and '''adjunct''' (adj), for general adjuncts, including time, location and manner.
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The current set of relations is presented in [[Relations]]
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Latest revision as of 19:08, 16 August 2013

The specifications here stated are still experimental and tentative, and have been continuously extended and amended in order to be as comprehensive as possible. They follow the general strategies defined in the UNL 2005 Specifications (version of June 7th, 2005), but introduce several important changes derived from different UNLization experiences. Although formally adopted in the UNDL Foundation tools, projects and certificates, they should not be taken yet as the official specs, as they are still under construction and have not been widely discussed with the UNL Community.

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