*** Guide-to-Links ***
W is used to attach main clauses to the wall (hereafter "the wall"
means the left-wall). Almost all kinds of main clauses -
declaratives, most questions (object-type, subject-type,
where/when/why, and prepositional), and imperatives - use a W
of some kind to attach to the wall. The only exception is
"yes-no" questions, which attach to the wall with Q. See "Q".

  |          |
/////	The dog ran (Wd)
/////	    Who did you hit (Wq)
/////	    Who is coming (Ws)
/////	     To whom did you speak (Wj)
/////	     Go away (Wi)

Note that the wall is automatically inserted at the beginning
of every sentence, and is then treated like a normal word; by
the connectivity rule, therefore, it must make some kind of
connection to the sentence. The wall thus has "W+ or Q+". 

W is also used to attach clauses back to coordinating
conjunctions in declarative sentences; coordinating
conjunctions thus have "CC- & (Wd+ or Wq+ or Ws+)". CC then
makes a link back to the subject of the previous main

Wd: Declarative Sentences
Wd is used in ordinary declarative sentences, to connect the
main clause back to the wall (or to a previous coordinating
conjunction). Nouns carry Wd-, optionally conjoined with their
S+ connectors. Wd- on nouns is directly disjoined with C-
(used in dependent clauses) and R- (used in some relative
clauses); see "C".

	dog: (({@CO-} & Wd-) or ({@CO-} & C-) or R+) & S+

Wq, Ws, Wj: Questions 
Wq, Ws and Wj are used to connect many types of questions to
the wall: subject questions (Ws), object questions (Wq),
where/when/why questions (Wq), adjectival questions (Wq), and
prepositional questions (Wj).  Each of these link types
interacts heavily with post-processing.  See "SI" for an
explanation of Wq and Ws; see "JQ" for an explanation of Wj.

Wi: Imperatives
Wi is used to connect imperatives to the wall.

     |   |
  /////  Go away

Imperative verb forms have "Wi-", conjoined with their
complement connectors. Since the imperative verb form is
always the same as the infinitive form (and the plural,
in every case except "be"), the same expression can be
used. Infinitive verbs thus carry

	(Sp- or I- or Wi-) & [complement];

Coordinating Conjunctions
There are a number of words that serve to link clauses together:
coordinating conjunctions like "and" and "but", and subordinating
conjunctions like "after" and "because".

          |        |   |
	John left but he returned later

               |    |   |
	John left after I saw you

Note that subordinating and coordinating conjunctions use very
different linking structures. First of all, both the left-pointing
and right-pointing connectors on the conjunctions are different;
"but" has "CC- & Wd+", "after" has "MVs- & Cs+". Secondly, 
coordinating conjunctions connect back to the subject of the
previous clause, subordinating conjunctions to the verb.
There are several reasons for making these distinctions.
First of all, coordinating conjunctions may not be used in
relative clauses:

	*The man I tried to hit but Jane stopped me is here
	*The man I tried to stop Jane but she hit is here
	*The man I hit but Jane comforted is here

(There are other constraints on relative clauses: the main
noun of a relative clause may not link to something inside an
embedded clause.  We handle this using Ce and Cs; see "C".)
So, we need to prevent these constructions. Coordinating
conjunctions have another related property. They may be used
to connect clauses in sequence, like subordinating
conjunctions. But whereas subordinating conjunctions seem to
link in a nested way, with each modifying the last,
coordinating conjunctions seem to "leap" over any preceding
subordinating conjunctions:

          |            |   |   |      |     |     |
     1.	John screamed when I arrived after Sue  left (seems right)

                           +---- ? ---+
          +------------+-C-+-S-+      +--W--+--S--+
          |            |   |   |      |     |     |
     2.	John screamed when I arrived but   Sue   left (seems wrong)

          +------------+-C-+-S-+      +--C--+--S--+
          |            |   |   |      |     |     |
     3.	John screamed when I arrived but   Sue   left (seems right)

We handle this in the following way. In the first place,
coordinating conjunctions link to the left not with MVs-, like
other conjunctions, but with CC-.

	and but: CC- & W+;
	dog: {R- or C- or (W- & {CC+})} & S+...;

Note that subject nouns may make a CC connection to the right,
but only if a W is being made to the left (i.e., if the noun
in a subject of a main clause), not if a C is being made. In
other words, while subordinating conjunctions connect to the
main verb of the nearest clause to the left, coordinating
conjunctions connect to the subject of the nearest main
clause to the left.  Thus ex. 3 above is allowed, but ex. 2 is
prevented. The problem with relative clauses is solved also.
In relative clauses, the main subject of the relative always
makes either a C- or an R- to the left, and neither one is
conjoined with CC+; so no coordinating conjunctions can

Note that the above expressions also allow coordinating
conjunctions to link clauses in sequence:

          |            |    |       |   |
	Jane screamed and Fred ran but Dave cried

Coordinating conjunctions may also connect directly to the
wall: "And Jane screamed". Thus they carry a "Wc-" connector,
which can link to the wall's W+. Furthermore, a coordinating
conjunction may link to a following question, rather than to a
declarative clause. They may not, however, link from a
question to a declarative clause:

I know you don't like Joe, but why did you send him that nasty note
*Why did you send Joe that nasty note, but I know you don't like him

Thus we give such conjunctions the following:

	(CC- or Wc-) & (Wd+ or Wq+ or Ws+ or Qd+);

Another reason for distinguishing between W and C is that
certain openers like participle openers may be used in main
clauses but not dependent ones; see "CO: Participles as openers".

Some of the uses of coordinating conjunctions using CC are
duplicated by "fat-link" parses: the special hard-wired system
for handling conjunctions (see the "Introduction" document for
explanation). A sentence like "Jane screamed and Fred ran"
will therefore receive two parses, one using "fat-links" and
the other using regular links.

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