View source for S-rule

'''S-rule''' (syntactic/semantic rule) is a specific type of [[transformation rule]] used for dealing with [[syntactic relations]] and [[semantic relations]] in the UNL framework.

== When to use S-rules ==
S-rules are used for altering, replacing, creating and deleting non-linear relations.

== When not to use S-rules ==
S-rules are not used for for linear relations (such as affixation, string manipulation and list manipulation, which must be addressed by [[A-rule]]s, [[N-rule]]s and [[L-rule]]s, respectively).

== Types of S-rules ==
{{:Transformation over relations}}

== Properties ==
#S-rules always end in ";"
#*rel("a");
#*<strike>rel("a")</strike>
#Relations are n-ary, i.e., they may have as many arguments as necessary, isolated by semicolon (";")
#*rel("a"); (relation with one argument)
#*rel("a";"b"); (relation with two arguments)
#*rel("a";"b";"c"); (relation with three arguments)
#*etc.
#:Syntactic relations are not predefined, although we have been using a set of binary relations based on the [[syntactic relations|X-bar theory]].
#:Semantic relations constitute a predefined and closed set that can be found [[Universal Relations|here]].
#Inside each relation, nodes may be referenced by any of its elements, isolated by comma (,):
#:VC(%a;%b) - syntactic relation between a node where index = %a and another node where index = %b
#:agt("a",[a],<nowiki>[[a]]</nowiki>,A;"b",[b],<nowiki>[[b]]</nowiki>,B) - semantic relation between a node having the feature A where string = "a" AND headword <nowiki>[a]</nowiki> AND UW = <nowiki>[[a]]</nowiki> AND another node having the feature B where string = "b" AND headword = [b] AND UW = <nowiki>[[b]]</nowiki>
#The arguments of a relation may be empty in case they are not affected by S-rules.
#:rel(;):=rel2(;); (replace all relations rel by rel2, regardless of their arguments)
#Relations may be conjoined through juxtaposition:
#:agt(%x;%y)obj(%x;%z) - two semantic relations: one between (%x) and (%y) AND other between (%x) and (%z)
#:<strike>VC([a];[b]),VC([a];[c])</strike> - conjoined relations must not be isolated by comma
#Relations may be disjoined through {braces}
#:{("a")|("b")}("c") - either ("a")("c") or ("b")("c")
#:{agt(%x;%y)|exp(%x;%y)}obj(%x;%z) - either agt(%x;%y)obj(%x;%z) or exp(%x;%y)obj(%x;%z)
#Order is not important between relations, but essential between arguments of the same relation
#:rel1("b")rel2("c")rel3("d") = rel2("c")rel3("d")rel1("b") = rel3("d")rel2("c")rel1("b")
#:rel1("a";"b"); '''&ne;''' rel1("b";"a");
#Relations may be replaced by regular expressions
#:/.{2,3}/(%x;%y) - any relation made of two or three characters between %x and %y
#Arguments of relations may be expressed by [[A-rule]]s, but only in the right side of rules 
#:rel("a"):=rel("an"); or rel("a"):=rel(0>"n");
#S-rules do not affect nodes unless explicitly informed
#:rel("a",[a],[[a]],A,%x;"b",[b],<nowiki>[[b]]</nowiki>,B,%y):=rel2(%x;%y); (the nodes %x and %y do not undergo any change)
#:rel("a",[a],[[a]],A,%x;"b",[b],<nowiki>[[b]]</nowiki>,B,%y):=rel2(%x);  (the node %x does not undergo any change; the node %y is deleted)
#:rel("a",[a],[[a]],A,%x;"b",[b],<nowiki>[[b]]</nowiki>,B,%y):=rel2(%x,-A;%y); (the feature A is removed from the node %x; all the rest, including the node %y, does not undergo any change)
#"^" is used for negation
#:rel1(%x;%y)^rel2(%y;%z):=+rel2(%y;%z); (if there is a rel1 between the nodes %x and %y and there is no relation rel2 between the nodes %y and %z, create a new relation rel2 between the nodes %y and %z)

== Indexes ==
See [[Indexation]]

== Examples ==
Examples of S-rules:
*composition
**VA("into account",PP); (add the PP "into account" as the adjunct of the verb)
*subcategorization
**VC(PH([in])); (the complement of the verb is a prepositional phrase headed by the preposition "in")
*agreement
**VS(ANUM,APER); (the specifier of the verb assigns number (ANUM) and person (APER) to its head
*case marking
**VS(NOM); (the specifier of the verb receives the case nominative (NOM)
*distribution
**VA(>>); (the adjunct of the verb comes at the right side of the verb after a blank space)
*adjacency
**VA(AJ2); (the adjunct of the verb integrates the second projection of the head)
*periphrasis
**VH(%vh,FUT):=+IC([will];%vh,+INF);
*projection
**VS(%head;%spec)VB(%head;%comp):=VP(VB(%head;%comp);%spec); (integrate the two relations on the left side into a single relation)
*mapping
**agt(%source;%target):=VS(%source;%target); (the agent relation is mapped into a VS relation)

== Formal Syntax ==
S-rules comply with the following formal syntax: 

 <<nowiki>S-RULE</nowiki>>                ::= <CONDITION> ":=" (<RELATION>)+";"
 <CONDITION>             ::= <TAG>(","<TAG>)* | (<RELATION>)*
 <RELATION>              ::= <SYNTACTIC RELATION> | <SEMANTIC RELATION>
 <SEMANTIC RELATION>     ::= <UNL RELATION> "(" <NODE> ";" <NODE> ")"
 <SYNTACTIC RELATION>    ::= <NL RELATION> "(" (<NODE>";")? <NODE> ")"
 <UNL RELATION>          ::= {one of the head-driven semantic relations defined in the [[Universal Relations|UNL Specs]]}  
 <NL RELATION>           ::= {one of the head-driven syntactic relations defined in the [[Tagset|UNDLF Tagset]]} 
 <NODE>                  ::= <FEATURE>(","<FEATURE>)* 
 <FEATURE>               ::= <ID>|<TAG>|"""<STRING>"""|"["<STRING>"]"|<DIRECTION>|<SYNTACTIC RELATION>|<ACTION>
 <ID>                    ::= "%"[a-zA-Z_0-9]+
 <TAG>                   ::= {one of the tags defined in the [[Tagset|UNDLF Tagset]]}
 <STRING>                ::= [a..Z]+
 <DIRECTION>             ::= ">"|">>"|"<"|"<<"
 <ACTION>                ::= <PREFIXATION> | <SUFFIXATION> | <INFIXATION> | <REPLACEMENT> (cf. [[A-rule]])
where<br />
<a> = a is a non-terminal symbol<br />
"a" = a is a constant<br />
a | b = a or b<br />
(a)? = a can be repeated 0 or one time<br />
(a)* = a can be repeated 0 or more times<br />
(a)+ = a can be repeated 1 or more times<br />