*** Guide-to-Links ***
R connects nouns to relative clauses. In subject-type
relatives, it connects to the relative pronoun. In object-
type relatives, it connects either to the relative pronoun
or the subject of the relative clause if the relative pronoun is

             |    |  |    |                       
     1. The dog  who I chased was black

             |   |     |
     2. The dog who chased me was black

             |   |     |
     3. The dog  I  chased was black

Consider the following simplified expressions:

	dog: ...(R+ & B+)... & (({C- or R-} & S+) or O+ or...);
	who: R- & (C+ or RS+);

When a relative pronoun makes a R connection back to a main
noun, it must make either a C connection to the subject of a
new clause (in an object-type relative - ex.1 above), or a RS
connection to a finite verb (in a subject-type relative -
ex. 2 above). Note that, conjoined with their S+ connectors,
nouns have not only C- but R-.  Thus, in object-type
relatives, the main noun can connect directly to the subject
of the relative clause; no relative pronoun is necessary
(ex. 3 above).

(Whereas the C- on nouns is conjoined with CO-, allowing
openers, the R- on nouns is not: "*The man apparently John
likes is here".)

As well as taking a relative clause, nouns may take modifiers
such as prepositional or participle phrases. Thus nouns have

        ...{@M+} & {R+ & B+ & {[[@M+]]}}...

This allows nouns to take one or more modifiers before the
relative clause; with cost 2, they can also take modifiers
after the relative clause (this is rare). (See "M: 'M'
modifiers used with relative clauses".)  We do not allow a
noun to take multiple relative clauses. These sound all right
in some cases ("The movie I saw that I told you about"), but
in practice seem to be extremely rare.

Other Words with "(R+ & B+)" 
Some pronouns and determiners which act as noun phrases have a
"R+ & B+" complex also: "ALL who apply for the job will be
considered", "We need SOMEONE who can program well".

Relative clauses may also occur within commas ("Dave, who you
met yesterday, is here". In this case, however, a very
different structure is formed. See "MX#r".

Relative Clauses and Post-Processing 
When a relative clause is created, an 'r' domain is begun, by
the R link between the main noun and relative pronoun. This
'r' domain spreads through the relative clause, and then
through the B link hooking back to the main noun.

	     +-----B(r)-+        |
	     +R(r)+RS(r)+-O(r)+  |
             |    |     |     |  |
	The dog  who chased  me was black        

The point of the 'r' domain is to include all the links
involved in the relative clause.  By ordinary domain logic,
however, after spreading back through the B link, the domain
would then continue to spread to the S link in the main clause
and everything else to the right. This is clearly
undesireable. We therefore create a special list of
"restricted links" in post-processing. These are links through
which domains are traced no further, when they extend back to
the left of the root word (the word on the left end of the
domain-starting link: the main noun, in this case).

Cycles in Relative Clauses
It will be noted that the linkages of relative clauses involve
"cycles"; more links are present than are necessary to
simply connect all the words.  Why is the cycle needed? In
object-type relatives, it seems natural for the main noun to
connect to the verb of which it is the implied object. But by
requiring a connection to the subject of the relative clause
as well, we can prevent question inversion at the linkage
stage ("*The dog did Jane chase was black"); hence the C+ on
relative pronouns.  Once we require the relative pronoun to
connect to the right in object-type relatives, we must let it
connect to the right in subject-type relatives as well; hence
the "RS" connector. (There is another motivation for the RS
connector, involving embedded clauses within relatives: see

As always with cycles, however, there is a danger here of
strange ill-formed sentences arising, such as "The dog I died
Jane chased was black". To prevent this, we include Bp and Bs
in a list of "MUST_FORM_A_CYCLE" links.  Post-processing then
insists that these links can only be used in cycles.

Special Uses of R
It was mentioned that R is used when the noun connects to the
subject of the relative clause rather than to the relative
pronoun.  R is also used for transitive infinitival phrases
following nouns: "The TEAM TO beat is Miami". This
construction is very rare and is given a cost of 2.

There are certain modifiers which may precede noun-phrases
(even pronouns), like "even" and "only". 

	  +--Wd-+-Rx+--Sp-+---I--+--Os-+    |
	  |     |   |     |      |     |    |
	///// only you would.v say.v that ///// 

These are not openers: they cannot be followed by a comma
("*Only, you would say that"), and they can be used in
relative clauses ("That is a face only a mother could
love"). Since the R- on nouns is disjoined with CO-, it is
convenient to use it in these cases. "Even" and "only" thus take
R+, connecting to following subject; they then make another
R link to the antecedent in relative clauses, and a C or W
link to the left in other kinds of clauses. The R- and the R+
on "even"/"only" are subscripted differently, as Re and Rx, to
prevent "*...a face only only a mother could love".

"Rw" is used similarly to Ct, Cta, and Rn to link question words to
the relative clauses that follow them.

For auxillary verbs, one has "(Rw- or Q-}".
For nouns and others, one uses "(Rw+ & B*m+)" (for any *)
For who,what,which,whom, one uses "(R+ & B*+)" (for any *)

      |     +----PP---+    
      +--Rw-+SIp*+    |    
      |     |    |    |    
     what  have  I  done ? 

See also:
* Mj: Prepositional-object relative clauses

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