Universal Networking Language (UNL)
Specifications
Version 2005

7 June 2005
Copyright ©  UNL Center of UNDL Foundation

Introduction to UNL 2005

UNL is an acronym for “Universal Networking Language”.

UNL is a computer language that enables computers to process information and knowledge across the language barriers. It is an artificial language that replicates the functions of natural languages in human communication. As a result, it enables people to express all knowledge conveyed by natural languages. It also enables computer to intercommunicate, thus providing people with a Linguistic Infrastructure (LI) for distributing, receiving and understanding multilingual information. Such multilingual information can be accessed by natural languages through the UNL System.

UNL is a language for representing information and knowledge provided by natural languages. It has all the components corresponding to that of a natural language. It is composed of words expressing concepts called "Universal words", also referred to as UWs that are inter-linked with other UWs to form the UNL expressions of sentences. These links, called as "relations", specify the role of each word in a sentence. The subjective meanings intended by the author are expressed through "attributes".

When computers make intelligent processing based on knowledge including reasoning, enough knowledge must be provided in the form that accessible and understandable for computers. We call the collection of such knowledge “Knowledge Infrastructure (KI)”. UNL 2005 is improved for meeting this need that UNL must be able to represent knowledge for providing intelligent processing with KI.

Major enhancements of UNL 2005 are the following:

UNL 2005 Specifications consists of eight documents. They are the following:

  1. UNL Expression

UNL expresses information or knowledge in the form of semantic network. In the UNL semantic network, nodes represent concepts and arcs represent relations between concepts. Concepts can be annotated. Such semantic network is called "UNL expression".

The unit of UNL expression is a UNL document. A UNL document is considered as a hyper-node composed of a semantic network among sentences or paragraphs. A paragraph and a sentence are hyper-nodes too. A hyper-node of a paragraph is composed of a semantic network among sentences or other paragraphs. A hyper-node of a sentence is composed of a semantic network among Universal Words (UWs) and scopes (hyper-nodes of compound concepts). Reference among UWs, sentences and paragraphs, and relations between sentences and/or paragraphs are possible to describe in UNL 2005.

This document describes how UNL expresses information or knowledge and the descriptive formats of UNL document and UNL expression.

  1. Relations

Relations as well as UWs are used to describe objectivity information of sentences. There are many factors can be taken into account in choosing an inventory of relations between concepts. Different factors may lead to different sets of the relations. The UNL relations are basically selected according to the following principles: 1) necessary condition and 2) sufficient condition.

This document describe the definitions of relations and provides the whole list.

  1. Attributes

    Attributes are mainly for the purpose to describe the subjectivity information of sentences. They show what is said from the speaker’s point of view: how the speaker views what is said. This includes phenomena technically called “speech acts”, “propositional attitudes”, “truth values”, etc. Attributes are also used to express ranges of concepts such as a generic concept and so forth. In the UNL 2005, attributes to express logical expressions are newly introduced in order to strengthen the expressibility of the UNL.

    Relations and UWs are used to describe objectivity information of sentences. Attributes modify UWs or semantic networks (scopes of compound concepts) to indicate subjectivity information such as about how the speaker views these states-of-affairs and his attitudes toward them and to indicate the property of the concepts.

    This document describe the definitions of attributes and provides the whole list.

  2. Universal Words

Universal Words are words that constitute the vocabulary of UNL. A Universal Word (UW) is not only a unit of the UNL syntactically and semantically for expressing a concept but also a basic element for constructing a UNL expression of a sentence or a compound concept. Such a Universal Word is represented as a node in the semantic network of UNL expression.

This document describes how a concept of a UW is defined, how a UW for such a concept is represented, what kinds of types of UWs exist in order to deal with various kinds of knowledge provided by natural languages, and finally, how a compound concept (hyper-node) is expressed in a UNL expression (semantic network) are described.

  1. UNL Knowledge Base

UNL Knowledge Base (UNLKB) defines every possible relation between concepts. The possible relations are defined based on a hierarchy of UWs (UW System). The UW System is built up by inclusive relations between concepts according to property inference mechanism of concepts. The architecture of the UW System allows to introduce and define any concept no matter how particular or specific it is.

Such UNLKB is a semantic network comprising every directed binary relation between UWs. It plays two roles: 1) defines the semantics (concepts) of UWs, and 2) provides linguistic knowledge of concepts. Concepts of UWs and linguistic knowledge of the concepts are defined by possible relations each concept can have with others. Such UNLKB not only provides linguistic knowledge in the form that computer can understand but also provides the semantic background of UNL expressions, that is the UNLKB ensures the meanings of UNL expression.

This document describes how the UNLKB is structured and how it functions.

  1. Knowledge Representation in UNL

For the purpose that UNL can replicate the functions of natural languages in human communication, the UNL should also provides the mechanism for inferring “John is the author of the book” from “John wrote the book” for example. In this inference, not only the knowledge of meanings (concepts) of words used in sentences, but also the knowledge that can specify a concept like the sentence “An author is a person who write a book” provided are necessary.  Just like any natural language, UNL should provide various kinds of knowledge in an appropriate way so that computer can understand and use.

This document describes how various kinds of knowledge are to be organized and expressed in the UNL Knowledge System.

  1. Logical Expression in UNL

In this document, how UNL can be used as logical language for expressing logic and what expressive functions the UNL provides to describe logical expressions for reasoning are described. The function to express logical expressions in UNL and the mechanism of reasoning using UNL are essential functions to establish Knowledge Infrastructure based on UNL.

  1. UNL System

The UNL System consists of three major components: language resources, software for processing the language resources, and tools and systems for maintaining and operating the language processing software or language resources.

1) Language resources are divided into language dependent part and language independent part. Linguistic knowledge on concepts that universal to every language is considered language independent and to be stored in the common database UNLKB. Language dependent resources like word dictionaries and rules, as well as the software for language processing, are stored in each language server.

2) DeConverter and EnConverter are developed for each language and stored in each language server. Language servers are connected through the Internet.

3) Supporting tools for producing UNL documents can be used in a local PC. Such supporting tools operate with consulting language servers through the Internet. Verification of UNL documents can be carried out through the Internet or in a local PC. UW Gate for searching and maintaining the common database UNLKB operates through the Internet.

This document describes the architecture of the UNL system and mechanism of conversion of UNL.