Dictionary

The UNL-NL dictionaries are bilingual dictionaries linking UWs to natural language (NL) words. They can be unidirectional (UNL-to-NL or NL-to-UNL) or bidirectional (NL-to-UNL-to-NL). UNL-to-NL dictionaries are used for NL-ization, while NL-to-UNL are used for UNL-ization. In what follows, we present the current specifications for UNL-NL dictionaries. They are not mandatory but are required from those interested in using UNL Centre's and UNDL Foundation's tools. The features marked with an * are only supported by UNDL Foundation's tools.

General syntax

In the UNL System, the UNL-NL dictionaries are plain text files with a single entry per line in the following format:

[NLW]  {ID}  “UW”  (ATTR , ... )  < FLG , FRE , PRI >; COMMENTS

Where:

NLW

The lexical item of the natural language. Its format should be decided by the dictionary builder. It can be:

• a multiword expression: [United States of America]
• a compound: [hot-dog]
• a simple word: [happiness]
• a simple morpheme: [happ]
• a non-motivated linguistic entity: [g]
• a complex structure (see below)*: [[bring] [back]]
• a regular expression (see below)*: [colou{0,1}r]

ID

The unique identifier (primary-key) of the entry.

UW

The Universal Word of UNL. This field can be empty if a word does not need a UW. It can also be a regular expression.

ATTR

The list of features of the NLW. It can be:

• a list of simple features: NOU, MCL, SNG
• a list of attribute-value pairs*: pos=NOU, gen=MCL, num=SNG
• a list of inflection rules (see below)*: IFX(PLR:=”oo”:”ee”)

Attributes should be separated by “,”.

FLG

The three-character language code according to ISO 639-3.

FRE

The frequency of NLW in natural texts. Used for natural language analysis (NL-UNL). It can range from 0 (less frequent) to 255 (most frequent).

PRI

The priority of the NLW. Used for natural language generation (UNL-NL). It can range from 0 to 255.

COMMENT

Any comment necessary to clarify the mapping between NL and UNL entries. It should end with the return code.

The features marked with * are not supported by the UNL Centre's tools

Formal syntax

<dictionary entry> ::= <NLW><ID><UW><FEATURE LIST>”<”<FLG>”,”<PRI>”,”<FRE>”>;” 

<NLW>::= “[”(<SIMPLE NLW>|<COMPOUND NLW>|<REGULAR EXPRESSION>)”]”
<SIMPLE NLW> ::= <text>
<COMPOUND NLW> ::= (“[”<text>”]”)+
<ID> ::= “{”<positive integer>”}”
<UW> ::= “””<text>”””|<REGULAR EXPRESSION>
<FEATURE LIST> ::= “(”<FEATURE> (”,”<FEATURE>)+”)”
<FEATURE> ::= (<VALUE>|<ATTRIBUTE>”=”<VALUE>|<RULE LIST>|”#”<SUBNLWID><FEATURE LIST>)
<SUBNLWID> ::= [01..99]
<RULE LIST> ::= <RULE>(”;”<RULE>)*
<RULE> ::= <ATTRIBUTE>”(”<VALUE>”:=”<a-rule>(”;”<VALUE>”:=”<a-rule>)*”)”
<ATTRIBUTE> ::= <text>
<VALUE> ::= <text>(”&”<text>)*
<FLG> ::= ISO 639-3 language codes
<PRI> ::= [0..255]
<FRE> ::= [0..255]
<REGULAR EXPRESSION> ::= "/"<PERL COMPATIBLE REGULAR EXPRESSIONS>"/"

Where:
+ = 1 or more times
* = 0 or more times
| = alternative
Horizontal blank spaces are allowed and ignored except inside quoted text (string literals).

Complex structures as NLW*

In order to deal with multiple word expressions, the NLW can be represented as a complex structure comprising several sub-NLW entries. The syntax for complex NLWs is:

[[sub-NLW][sub-NLW]...[sub-NLW]]  {ID}  “UW”  (ATTR , ..., 01#(ATTR, ...), 02#(ATTR, ...), ...)  < FLG , FRE , PRI >; COMMENTS

Where:
[sub-NLW] is a part of the NLW;
01#(ATTR, ...) are the specific features for the first sub-NLW to appear in the NLW;
02#(ATTR, ...) are the specific features for the second sub-NLW to appear in the NLW;
and so on.
The first sub-NLW to appear in a NLW will be always the 01, the second the 02, and so on.
The feature list preceded by <number># will apply only to the corresponding sub-NLW.
The features outside the sub-NLW feature lists are shared by all sub-NLWs.

Example

[[bring] [back]] {12343} "to bring back(icl>to bring)" (pos=VER, 01#(IFX(ET0:=4>"ought")), 02#(pos=PRE)) <eng, 0, 0>;

In the entry above, the NLW has been split into two different sub-NLWs ([bring] and [back] with a blank space in between). Each of these sub-NLWs has different features, referred to in the embedded parentheses inside the feature list. The sub-NLW [bring], which was the first to appear, has the feature "IFX(ET0:=4>"ought")", while the sub-NLW [back], which was the second, has the feature "pos=PRE". The feature "pos=VER", which is outside the specific feature lists, is shared by both of them.

Inflection rules inside dictionary entries*

In order to deal with exceptions and irregular forms, dictionaries may contain rules, which must be included inside the feature list, as follows:

<RULE> ::= <ATTRIBUTE>”(”<VALUE>”:=”<a-rule>(”;”<VALUE>”:=”<a-rule>)*”)”

Where:
<ATTRIBUTE> is the attribute that will be used to call the rule
<VALUE> is the value of the attribute that will trigger the rule
<a-rule> is an affixation rule (described in a-rule)

Scope of inflection rules

Inflection rules always apply over the entry of dictionaries. In UNL-ization dictionaries (i.e, from natural language into UNL), the entry is always a UW; in NL-ization dictionaries (from UNL to natural language), the entry is always a NLW. This means that a single rule may apply either to the field <NLW> or <UW>. Accordingly, the entry
[aaaaa] "bbbbb" (ATT(VAL:=0>"ccccc")) <eng,0,0>;
will produce the following results (provided that the value "VAL" is assigned to the attribute "ATT" in both cases):

• In UNL-ization (analysis): "bbbbbccccc" (i.e., the UW "bbbbb" will be transformed);
• In NL-ization (generation): "aaaaacccccc" (i.e., the NLW "aaaaa" will be transformed).

Examples of inflection rules

NUM(PLR:="men")

If the value of the attribute "number" (NUM) is "plural" (PLR) then replace the whole natural language word by "men"

POS(ORD:="1">"1st","2">"2nd","3">"3rd")

If the value of the attribute "part of speech" (POS) is "ordinal" (ORD) then:

if the last character of the string is "1", then replace "1" by "1st"; and

if the last character of the string is "2", then replace "2" by "2nd"; and

if the last character of the string is "3", then replace "3" by "3rd".

Regular expressions inside dictionary entries*

Both the NLW and the UW may be replaced by Regular Expressions. In both cases, regular expressions must be included between a pair of "/" and should comply with the PCRE - Perl Compatible Regular Expressions]. They should be represented as follows:

Regular expression in NLW (used in UNL-ization)

[/<RegEx>/] "<UW>" (<FEATURE LIST>) <LANG,FRE,PRI>;

Regular expression in UW (used in NL-ization)

[<NLW>] "/<RegEx>/" (<FEATURE LIST>) <LANG,FRE,PRI>;

Examples

Regular expressions in NLW

[/colo(u)?r/] "color" (POS=NOU) <eng,0,0>; (NLW = {color, colour})

[/cit(y|ies)/] "city" (POS=NOU) <eng,0,0>; (NLW = {city, cities})

[/(\d){4}/] "" (ENT=YEAR) <eng,0,0>; (NLW = any sequence of four digits)

Regular expressions in UW

[city] "/city(.)*/" (POS=NOU) <eng,0,0>; (UW = any UW that starts by the string "city")

[city] "/(.)\(iof\>city\)/" (POS=NOU) <eng,0,0>; (UW = any UW that ends by the string "(iof>city)"

Examples of dictionary entries

[China]{24} "China(iof>Asian country)" (NOU, WRD, SNG, P0, F0) <eng,0,0>;
[choose]{106} "to choose(icl>to decide)" (POS=VER, LEX=WRD, INF=P1, FRA=F76, FLX(3PS&PRS&IND:=0>"s"; PAS:="chose"; PTP:="chosen"; GER:="choosing")) <eng,0,0>;
[clear-eyed]{25} "clear-eyed(icl>discerning)" (POS=ADJ, LEX=WRD, INF=P0, FRA=F0) <en,0,0>;
[Peter]{177}"Peter(iof>person)"(NOU)<eng,10,30>;
[kill]{5987}"kill(icl>do)"(TEN(PAS:=0>"ed"))<eng,70,80>;
[[bring] [back]]{2345}"bring back"(POS=VER,01#(POS=VER,TEN(pas:=3>"ought")),02#(POS=PRE))<eng,50,34>;
[/br(ing|ought)/] "bring(icl>do)" (POS=VER) <eng,0,0>;
[[/br(ing|ought)/] [back]]{2345} "bring back(icl>do)" (POS=VER,01#(POS=VER),02#(POS=PRE))<eng,50,34>;
[/colo(u)?r/] "color" (POS=NOU) <eng,0,0>; (NLW = {color, colour})
[/cit(y|ies)/] "city" (POS=NOU) <eng,0,0>; (NLW = {city, cities})
[/(\d){4}/] "" (ENT=YEAR) <eng,0,0>; (NLW = any sequence of four digits)
[city] "/city(.)*/" (POS=NOU) <eng,0,0>; (UW = any UW that starts by the string "city")
[city] "/(.)\(iof\>city\)/" (POS=NOU) <eng,0,0>; (UW = any UW that ends by the string "(iof>city)"