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<b>Composition rules</b> (CPWR) are used to generate compounds out of the base form.

== When to use composition rules ==
Composition rules must be created when and only when the [[base form]] is different from the [[lemma]].<br />
This situation occurs only in case of the following [[multiword expression]]s:
*when inflections are formed by infixation (in opposition to simple suffixation or prefixation); or
*when the multiword expression is discontinuous.
For instance:<br />
The English multiword expression "call for" has the following inflections: "call for", "call'''s''' for", "call'''ed''' for", "call'''ing''' for", etc. These inflections are formed by infixation, in the sense they apply in the middle of the expression (between "call" and "for"). If we simply associate this expression to the inflectional paradigm of "call", we will have the following results: "call for", "call for'''s'''", "call for'''ed'''", "call for'''ing'''", etc. In order to prevent this problem, and to avoid the unnecessary proliferation of rules in the grammar, we split the multiword expression into two segments: the '''base form''' (BF), i.e., the term over which the inflections will be directly applied; and the '''composition rule''' (CPWR), which is the rule used to rebuild the lemma out of the base form. In the case of "call for", the lemma is "call" and the composition rule is "VH([for],P,M0);".

== When not to use composition rules ==
Composition rules must not be used in the following circumstances:
*When the word is not a multiword expression;
*When the multiword expression is invariant;
*When the inflections of the multiword expression are formed by prefixation or suffixation (such as in "call center" > "call center'''s'''");

== How to create a composition rule ==
The syntax for composition rules is the following:
 <SYNTACTIC ROLE>(<ADDED>,<FEATURES);
Where:<br />
*<SYNTACTIC ROLE> is the [[syntactic role]] (VA, VC, VS, VH, etc) of the term to be added to the base form;
*<ADDED> is the term to be added to the base form to form the compound. It must be represented between <nowiki>[</nowiki>brackets<nowiki>]</nowiki>, if it is a lemma (i.e., if it is an entry in the dictionary), or between <nowiki>"</nowiki>quotes<nowiki>"</nowiki>, if a string (i.e., if it is not an entry in the dictionary)
*<FEATURES> are the features of the term to be added to the base form. The following features are mandatory:
**the [[lexical category]] (A,J,N,V,C,P,D) of the term to be added
**the [[inflection|inflectional properties]] (paradigm and/or inflectional rules) of the term to be added
**the [[distribution]] (i.e., the position) of the term to be added, if not default
**the [[adjacency]] of the term to be added, if not default
There can be several different composition rules associated to the same base form in order to form complex expressions such as "give up the ghost", where there are at least three constituents: "give", which is the base form; and "up" and "the ghost", which will part of different composition rules:
*VH([up],P,M0);VC("the ghost",N,M0);

== Examples of composition rules == 
*VH([in],P,M0); (add the lemma [in], which is a preposition (P) and invariant (M0), as part of the head of the verbal phrase (VH), as in "give">"give in")
*VA("into account",A,M0); (add the string "into account", which is an adverb (A) and invariant (M0), as an adjunct to the head of the verbal phrase (VA), as in "take">"take into account")

== Composition rules in the dictionary ==
In the UNL<sup>arium</sup> framework, composition rules may be expressed in two different formats:
*As complex structures, such as<ref>For further information on complex structures inside the dictionary, refer to [[Dictionary Specs#Complex structures as NLW*]]</ref>
 [[sub-NLW][sub-NLW]...[sub-NLW]]  {ID}  “UW”  (ATTR , ..., #01(ATTR, ...), #02(ATTR, ...), ...)  < FLG , FRE , PRI >; COMMENTS
*As simple structures, such as
 [NLW]  {ID}  “UW”  (ATTR , ..., BF=<BASE FORM>, CPWR=MTW(<COMPOSITION RULE>) )  < FLG , FRE , PRI >; COMMENTS
Where <COMPOSITION RULE> is the rule or set of composition rules used to form the lemma out of the base form, and <BASE FORM> is the [[base form]]. Notice that the compostion rule must be informed as a value of the attribute CPWR and should be preceded by the multiword tag MTW because there can be several different composition rules associated to the same entry.

== Example of dictionary entries containing composition rules ==
*[[bring] [back]] {12343} "202078294" (pos=VER, #01(IFX(ET0:=4>"ought")), #02(pos=PRE)) <eng, 0, 0>;
*[bring back] {12343} "202078294" (pos=VER, BF=bring, CPWR=MTW(VA([back],A,M0);)) <eng, 0, 0>;

== Notes ==
<references />