A new UNL Explorer has been developed and is provided at www.undl.org/unlexp/ and www.unl.undl.org/unlexp/ by the UNL Center.

The UNL Explorer is a UNL-based Multilingual Intelligent Information and Knowledge Management System.

The UNL Explorer provides users with an integrated environment that users can search for and edit knowledge and information based on UNL.

Using the UNL Explorer, search for information of UNL Encyclopedia can be made by content, keyword or keyconcept search, or though navigation of the UW System of the UNL Ontology

The UNL Explorer has the following characteristics:

Semantic Co-occurrence Relation Search

whether a relation between two UWs is true or not, what UWs can have a relation with another UW, or what relations are possible between two UWs can be verified based on the UNL Ontology.

UNL-based Semantic Network Search

Content search is carried out based on UNL Expressions.

Intensional Definition-based Inference

every UW is given an intentional definition to specify its all the essential properties. the definition is used in inference about all concepts it related.

Multilingual Information Processability

the UNL Explorer allows users to search for information described in whatever language using their native languages, or to provide or edit information using their native languages.

UNL Graphical Editability

A graphical editor of UNL Expressions works together with the UNL Explorer.

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UNL Specifications

The UNL Specifications define how UNL is and how the UNL System is. It consists of 8 chapters as follows:
  1. UNL Expression
  2. Relations
  3. Attributes
  4. Universal Words
  5. UNL Ontology (UNL Knowledge Base)
  6. Knowledge Representation in UNL
  7. Logical Expression in UNL
  8. UNL System

Chapter 1 describes the description format of UNL Expressions. Chapter 2 describes what relations and how they are selected, and what are the roles of relations in UNL. Chapter 3 describes what information attributes express in UNL, what kinds of attributes there are, and how they are decided. Chapter 4 describes how a concept is defined, how an UW for a concept is created, what kinds of UWs exist for expressing various meanings of natural languages, and how a compound concept (hyper node or scope) is expressed in UNL. Chapter 5 describes how the UNL Ontology is constructed, what information it provides and how, and what roles it plays in the UNL System. Chapter 6 and 7 describe how different levels of knowledge is considered and dealt with, and how logic expressions are expressed in UNL. Chapter 8 describes the architecture of the UNL System and conversion mechanism between UNL and natural languages. 

Version II (2014) http://www.undl.org/unlsys/unl/
Previous versions 
     2005 http://www.undl.org/unlsys/unl/unl2005-e2006/
     3.3 http://www.undl.org/unlsys/unl/UNLSpecs33.pdf

UNL Manual

How to express it in UNL?

This manual is meant to complement and clarify the UNL Specifications. A variety of examples from different languages are used to explain how each component mainly relation or attribute should be used, and how the UNL Expressions should be for various meanings. The manual is arranged and orgnaized according to grammatical phenomena of natural language.

This manual consists of 6 chapters. Chapter 1 explains the informational structure of UNL, how UNL deal with verious information of natural languages. Chapter 2 explains what kinds of UWs exist in UNL. Chapter 3 explains how UNL Expression should be for representing a sentence or a hyper node. Relations are explained in chapter 4, a comparison with closer relations is made to help to understand each relation. Attributes are explained in chapter 5, focusing on what kinds of attributes exist and how each is used using exampls of different languages. The last chapter 6 explains how various meanings or expressions of natural languages are dealt with in UNL.

Latest version (2010) http://www.undl.org/unlsys/unlman2010/
Previous version (2001) http://www.undl.org/unlsys/unlman/

UW Manual

What is a UW?
What is the structure of a UW?
How to define a UW?

These are the main questions we intend to clarify through this manual. It is meant to explain how to create and to define Universal Words. Through this manual, we hope not only to wide spread the knowledge on UNL, but also to reduce the number of wrong, inappropriate or redundant UWs.

Specifications of UWs are defined in chapter 4 of UNL Specifications. This manual is intended to be a guide, for educational purposes, to explain how to understand, create and define a UW. For fully understanding this manual, the thorough study of UNL Specifications is of the utmost importance.

Latest version (2010) http://www.undl.org/unlsys/uwman2010/
Previous version (2.0, 2003) http://www.undl.org/unlsys/uw/uwmanv20.htm

UNL Annotation

The aim of UNL Annotation is to clarify semantic structures of sentences. The purpose is to generate meaning representations of UNL of sentences without using language dependent grammatical information. Tags for UNL Annotation are designed to be language independent. By inserting the tags in sentences of a natural language, UNL Expressions can be generated from the (any) language using the Universal Parser. This document provides definitions of tags for UNL Annotation and explains how each tag is used.

Tags of UNL Annotation cover the following information:

  • Information on relations, attributes and UWs
  • Information on the roles of elements of a sentence
  • Information on the relation between elements of a sentence
  • Information on the scopes of a phrase, clause or compound word
  • Information on the reference

For details see http://www.undl.org/unlsys/uparser/UNLA.pdf (1.0, 2003).

Sentences annotated with tags of UNL Annotation are input of the Universal Parser. The Universal Parser is explained in the UNL System.


Universal Networking Language

ISBN 10 2-8399-0128-5
ISBN 13 978-2-8399-0128-4

Edition II
Authors : Hiroshi Uchida, Meiying Zhu, Tarcisio Della Senta
Published : 2005.6 by UNDL Foundation
Language : English

Image of Front Cover
Image of Front Cover
Image of Back Cover
Image of Back Cover

Table of contents

chapter 1 - UNL Expression
chapter 2 - Relations
chapter 3 - Attributes
chapter 4 - Universal Words
chapter 5 - UNL Knowledge Base
chapter 6 - Knowledge Representation in UNL
chapter 7 - Logical Expression in UNL
chapter 8 - UNL System


Chapters 1 - 5 describe the specifications of the UNL and UNL Documents, chapters 6 - 7 describe how the UNL express various kinds of knowledge and the mechanism of reasoning using UNL expressions, and chapter 8 describes the structure of the UNL System and explains its components. Chapter 8 also explains how to create the UNL Encyclopedia and introduces some method to create UNL Documents.

Information on how to get the book is provided at here.

The UNL, A Gift for a Millennium

ISBN 4-906686-06-0 C

Authors : Hiroshi Uchida, Meiying Zhu, Tarcisio Della Senta
Published : 1999.11 by UNU/IAS
Language : English

The UNL, A Gift for a Millennium

This book can be viewed at http://www.undl.org/publications/gm/index.htm.


  1. Hiroshi UCHIDA, Common Web Language, slides of presentation at SWIG of Technical Plenary and WG Meeting Week 27 Feb - 03 Mar 2006, 2 Mar 2006
  2. Hiroshi UCHIDA and Meiying ZHU, UNL2005 from Language Infrastructure toward Knowledge Infrastructure, special speech at PACLING, 2005.8
  3. Hiroshi UCHIDA and Meiying ZHU, UNL2005 for Providing Knowledge Infrastructure, invited speech at SeC2005 Workshop, Chiba, Japan, 2005.5.10
  4. Hiroshi UCHIDA, Knowledge Description Language(Japanese), presentation at Semantic Computing workshop at 12 Apr. 2003, Keio University, Tokyo of Japan, 2003.4.12
  5. Hiroshi UCHIDA, How to build Universal Knowledge, invited presentation at ICUKL-2002 at 25-29 Nov. 2002, Goa of India, 2002.11
  6. Meiying ZHU and Hiroshi UCHIDA, Universal Word and UNL Knowledge Base (paper), (slides), invited presentation at ICUKL-2002 at 25-29 Nov. 2002, Goa of India, 2002.11
  7. Ronaldo MARTINS, UNL as a linguistic point of view, invited presentation at ICUKL-2002 at 25-29 Nov. 2002, Goa of India, 2002.11
  8. Hiroshi UCHIDA, The Universal Networking Language Beyond Machine Translation. This paper was presented at the "International Symposium on Language in Cyberspace" held at 26 - 27 September 2001, Seoul of Korea, organized by The Korean National Commission for UNESCO and The Cyber Communication Academic Society in Korea, and sponsored by Institute of Information Technology Assessment, Rep. of Korea and UNESCO. For details of the symposium please look at http://www.unesco.or.kr/cyberlang. 2001.9


Slides for teaching DeConverter

These slides are for educational purpose on the DeConverter.

The following slides explain the function, the format or syntax of rule, the type of rule, the usage, etc. of the DeConverter, all knowledge that are necessary for using it.


The following slides show examples. Each slide shows a step-by-step process (trace) of deconversion of a sentence.



Examples of data for deconversion

Example 1

English DeCo rules (r.txt) deconversion rules that are necessary to deconvert the UNL of S:14 below.
English dictionary entries (d.txt) dictionary entries that are necessary to deconvert the UNL of S:14 below. Text data of dictionary entries must be converted into IBAM formatted files using DicBld.
UNL of S:14 of artile "Ethics and Science" example of UNL that can be deconverted using the rules and dictionary entries above.
Output deconversion result of English using above files.

Example 2

Dictionary entries dictionary entries that are necessary to deconvert the UNL of S:22 below. Text data of dictionary entries must be converted into IBAM formatted files using DicBld.
UNL of S:22 of article “Ethics and Science” example of UNL that can be deconverted using the rules included in the deconversion process below and dictionary entries above.
Deconversion process of S:22 is shown.

UNL Data

This list of UNL Documents is provided in chronological order of when they are made. The newest is the last of the list.

  1. UNL Documents of UNESCO documents and articles from WHC web site of UNESCO (2004)
  2. UNL Documents of Bibliography and Biography (2005-2006)
  3. UNL Documents for UNL-EOLSS Project (2007-2008)
  4. UNL Documents of articles from Wikipedia (2009-)