Top  UNL Expression   Relations   Attributes  Universal Words  UNLKB  Knowledge Representation in UNL  Logical Expression in UNL  UNL System 

UNL 2005 Specifications

7 June 2005
Copyright © UNL Center of UNDL Foundation

Chapter 5  UNL Knowledge Base

The UNLKB is a semantic network comprising every directed binary relation between UWs. All binary relations of the UNL KB are in the following format: 'relation(UW1, UW2)=c', where 'c' is the degree of certainty, which has the value 0 (impossible) or from 1 to 128 (certain). This binary relation means gUW1 takes UW2 as the relation in certainty value ch; or gUW2 plays the role specified by the relation to UW1 in certainty value ch.

5.1  Roles of the UNLKB

A UW is a label for a concept. Concepts labeled by UWs are defined by describing the set of possible relations that each concept can have with other concepts in UNLKB.  Definitions of possible relations of a concept with other concepts describe the behavior of the concept. This behavior is the property of a concept in the sense that the descriptions of behavior characterize the concept and provide enough information for understanding the semantic structure of a sentence which include the concept.

The behavior of a concept is considered as linguistic knowledge on the concept. This knowledge is used to provide semantic structure of sentences of natural languages. For example, an gauthorh is a gpersonh, who can take various actions that a person can take, such as writing something and something might be a book, and so forth. This level of knowledge is necessary to provide the semantic background of natural language sentences. Further knowledge, for example real world knowledge, will be established based on this linguistic knowledge, using the UWs.

In the UNLKB, the semantics of UWs are defined using the UW system and linguistic knowledge of concepts is provided also based on the UW System.

5.2  UW System

In the UNL KB, all UWs are linked with each other through 'icl' (subclass), 'iof' (element/instance), or 'equ' (equivalent) relations. 'Icl' links a UW of a subclass concept to the class concept UW; 'iof' links a UW expressing an instance to a UW of a class concept; and 'equ' links a UW to an equivalent UW. The UWs related to each other through 'icl', eioff and 'equ' relations make up a hierarchy of UWs. This hierarchy of UWs is the UW system. This UW system allows having multiple super-class concepts. Accordingly, the UW system is a lattice type of network.

The following table shows the functions that each relation of 'icl', 'iof' and 'equ' has in the UW System:

Table 5.1
icl The most important (frequently used) relation in constructing the UW system. It defines 1) a subset of a class concept, as in 'icl(Dixieland jazz, jazz(icl>music))=1', by which 'Dixieland jazz' is defined as a subset concept of 'jazz(icl>music)'; or 2) an equivalent of a more general concept, as in 'icl(check(icl>examine(agt>thing,obj>thing)), examine(agt>thing,obj>thing))=1', which defines 'check(icl>examine(agt>thing,obj>thing))' as an equivalent of a more general concept 'examine(agt>thing,obj>thing)'.
iof Defines an instance of a concept. For example 'iof(Tokyo, city(icl>region))=1' defines 'Tokyo' as an instance of concept 'city(icl>region)'.
equ Defines a completely equivalent UW with another UW. In the UNLKB, 'equ' is used to link a UW made up of an abbreviation to the UW made up of its full expression. For example as in 'equ(UNL(icl>Universal Networking Language), Unlversal Networking Languague)=1'.

5.3  Features of the UNLKB

The hierarchy of the UW system is constructed by taking the property inheritance and replacement by super-class concept mechanisms into consideration. In UW system, lower UWs inherit the properties of upper UWs; and upper UWs can replace lower UWs to convey a more general sense in a specific context of the lower UWs. All these inheritance and replacement are carried out through the relations 'icl', 'iof' and 'equ'.

In the UNLKB, all possible relations, such as 'agt', 'obj', etc, that an UW can have with others are defined for each UW. Every possible relation is defined between the two most general UWs of the two categories (of lower UWs) that can have the relation. Utilizing the property inheritance mechanism of the UW system possible relations of lower concepts are deductively inferred, and this inference mechanism can reduce the number of binary relations.

Replacement of lower UWs by upper UWs can cause problems by introducing ambiguities if the upper UWs are not close enough in meaning to the lower UWs. To avoid this, the upper UWs must be the closest UWs among all of the more general UWs . In other word, every UW must be positioned under the closest upper UWs.

5.4  Uses of the UNLKB

The UNLKB defines the syntax and semantics of the UNL. Such UNLKB is used in sentence analysis for disambiguation and in sentence generation for finding more general concepts when encountering a unknown concept to a target language. The UNLKB also is used to verify UNL expressions since it provides syntax and semantics of the UNL.

To fully utilize the functions of the UNLKB, all UWs (concepts) must be defined in the UNLKB. For convenience, the following templates are provided for defining UWs that express instances. With these templates, a UW that has the same restriction as one of these templates is not necessary to be defined in the UNLKB, and the corresponding template is used instead in referring to the UNLKB. For example, 'uw(iof>person)' is the template for 'John(iof>person)'.

Template UWs:

uw(iof>international organization)
uw(iof>numerical value{>value})
uw(iof>perfume{>functional thing})
uw(iof>person{>living thing})

5.5  Structure of the UW System

Table 5.2
1st Level 2nd Level 3rd Level 4th Level
Universal Word
nominal concept thing abstract thing
concrete thing
functional thing
pronominal thing
volitional thing
verbal concept be be(aoj>thing)
do do(agt>thing)
@ occur occur(gol>thing,obj>thing)
adjectival concept uw(aoj>thing) uw(aoj>abstract thing)
uw(aoj>concrete thing)
uw(aoj>functional thing)
uw(aoj>volitional thing)
uw(mod<thing) uw(mod<abstract thing)
uw(mod<concrete thing)
uw(mod<functional thing)
uw(mod<volitional thing)
@ uw(qua<thing)
adverbial concept how how(man<adjective concept)
ow(man<adjective concept,obj>thing
how(man<verbal concept)
how(man<verbal concept,obj>thing)

The general structure of the UW system is as follows:

First Level

The topmost level of the UW system is composed of one UW : the 'Universal Word' itself. The UW 'Universal Word' is hence the broadest UW among all, for it denotes a concept that includes every other concept. And 'uw' is an equivalent UW of 'Universal Word'. It is the abbreviated citation form of 'Universal Word', to which it is related by means of 'equ': 'equ(uw, Universal Word)=1'.

Second Level

Under 'uw' there are four UWs, directly related to 'uw' through 'icl'. These four UWs are the following: enominal conceptf, everbal conceptf, eadjective conceptf and 'adverbial concept'. They represent the four uppermost general categories under which the other UWs are to be represented inside.

Third Level

Each of these four uppermost UWs is subdivided in other different lower UWs, according to the following tables.

Under 'nominal concept' 'thing' is placed to represent all kinds of nominal concepts. This UW is very useful in expressing a relationship between a thing (whatever it is) and another concept.

'verbal concept' is divided into three categories headed by UWs 'do', 'occur' and 'be' according to the following features:

Table 5.3
UW [need an agent] [expend energy] English
'do' + + " to kill"
'occur' - + "to fall"
'be' - - "to know"

Each of these categories has the following features in terms of necessary relation to take:

Table 5.4
UW [necessary relation] English
'do' 'agt' " to kill"
'occur' 'obj' "to fall"
'be' 'aoj' "to know"

UWs 'be', 'do' and 'occur' are defined to take all possible relations that each category may take, as shown in the master definitions (MDs) below. With these UWs, all UWs that belong to each of these UWs are available to be defined under each of them.

Table 5.5



'be' be{(aoj>thing,and>uw,ben>thing,cao>thing,cnt>uw,cob>thing,con>uw,coo>uw,
dur>period,man>how,icl>verbal concept,obj>thing,or>uw(aoj>thing),plc>thing,
'do' do{(agt>thing,and>uw,ben>thing,cag>thing,cob>thing,con>uw,coo>uw,cnt>uw,
dur>thing,gol>thing,icl>verbal concept,ins>concrete thing,man>how,met>abstract 
'occur' occur{(and>uw,ben>thing,cob>thing,con>uw,coo>uw,cnt>uw,dur>do,dur>period,
dur>occur,gol>uw(aoj>thing),gol>thing,icl>verbal concept,man>how,obj>thing,

'adjective concept' is divided into two categories headed by UWs 'uw(aoj>thing)' and 'uw(mod<thing)' according to the following features:

Table 5.6
UW [predicative] [attributive] English
'uw(aoj>thing)' + - "along"
@ + + "beautiful"
'uw(mod<thing)' - + "total"

UWs 'uw(aoj>thing)' and 'uw(mod<thing)' are defined to take all possible relations that each category may take, as shown in the MDs below. With these UWs, all UWs that belong to each of these UWs are available to be defined under each of them.

Table 5.7



'uw(aoj>thing)' uw(aoj>thing{,and>uw,ben>thing,cao>thing,cnt>uw,cob>thing,con>uw,coo>uw,
rsn>uw(aoj>thing),rsn>do,icl>adjective concept})
'uw(mod<thing)' uw({and>uw,icl>adjective concept,}mod<thing)

Under 'adverbial concept' 'how' is placed to represent all kinds of adverbial concepts. This UW is very useful in defining a UW of adverbial concept.

Fourth Level

In this level, 'thing' is divided into the following categories: 'abstract thing', 'concrete thing', 'functional thing', 'place(icl>thing)', 'pronominal thing', 'time(icl>thing)', and 'volitional thing'.

A uw that expresses a nominal concept is linked under one or more than one of these categories. For example UW 'group(icl>abstract thing)' is defined also under 'volitional thing', as shown in its MD 'group(icl>abstract thing{,icl>volitional thing})'.

In this level, verbal concepts of 'be', 'do' and 'occur' are divided into different categories according to combinations of relations to take. The sorts of combinations in this level are considered basically among the eight relations : 'agt', 'aoj', 'gol', 'mod', 'obj', 'opl', 'ptn' and 'src'. Combinations with other relations that are thought important for determining the concepts of UWs are considered in next level under each of this level's UWs.

For example, table 5.8 shows the MD of UW 'do(agt>thing)'. By restriction 'icl>do', UW 'do(agt>thing)' is defined under 'do' and will inherit all relations that defined in 'do' (see MD of 'do' in table 5.5) except for 'gol', 'obj', 'ptn' and 'src' relations with a 'thing'.

Table 5.8

MD of 'do(agt>thing)'


Frame UWs

UWs that headed by 'be', 'do', 'occur', 'how' or 'uw' and defined for providing various combinations of relations are mainly used to define other UWs and are called "frame UWs". In the UW system, such frame UWs are prepared in various levels of the UW system and construct the skeletal structure of the UW system.

For example, the following shows MDs of UWs using 'do(agt>thing)' and 'do(agt>thing,obj>thing)'.



In this level, frame UWs for defining more strict adjective concepts are provided as in 'uw(aoj>abstract thing)', 'uw(aoj>concrete thing)', 'uw(aoj>functional thing)', 'uw(aoj>place)', 'uw(aoj>thing,bas>thing)', 'uw(aoj>thing,obj>thing)' and 'uw(aoj>volitional thing)'; and as in 'uw(mod<abstract thing)', 'uw(mod<concrete thing)', 'uw(mod<functional thing)', 'uw(mod<place)' and 'uw(mod<volitional thing)'. 

For example, UWs like ''heavy({icl>uw(}aoj>abstract thing{)})' to express the degree of something and 'heavy({icl>uw(}aoj>concrete thing{)})' to mean "weighing a lot" are defined using this level's frame UWs.

In this level, frame UWs for defining more strict adverbial concepts are provided as in 'how(man<quantity)', 'how(man<uw>adjective concept)', 'how(man<uw>verbal concept)', 'how(obj>thing)' and 'how(obj>uw)'. 

For example, UW 'before(icl>how(obj>uw))' to mean "(to do something) before doing something else" is defined using this level's frame UW.

Fifth and further Levels

Further levels' UWs including frame UWs are defined in the following three ways:

  1. Redefining a frame UW by replacing a partner UW with more strict one. For example, the UW 'do(agt>volitional thing)' is defined under 'do(agt>thing)' by MD 'do({icl>do(agt>thing),}agt>volitional thing)'. This frame UW is useful when defining a UW like 'act({icl>do(}agt>volitional thing{)})' that always taking a volitional thing as agent. Although 'act(agt>volitional thing)' can also be defined using 'do(agt>thing)' directly as 'act({icl>do(agt>thing),}agt>volitional thing)', but it is convenient to have a frame UW like 'do(agt>volitional thing)' if it is frequently used.
  2. Defining further specific frame UWs by specifying combinations with further relations.
  3. Linking synonymous UWs under the most general/popular one. For example, 'separate(icl>divide(agt>thing,obj>thing))' is defined under 'divide(agt>thing,obj>thing)' which is under 'do(agt>thing,obj>thing)'.

All these methods mentioned above are also can be said to all UWs that defined in 3rd and 4th levels.

Top  UNL Expression   Relations   Attributes  Universal Words  UNLKB  Knowledge Representation in UNL  Logical Expression in UNL  UNL System