*** Guide-to-Links ***
MV
MV connects verbs (and adjectives) to modifying phrases like adverbs,
prepositional phrases, time expressions, certain conjunctions,
"than"-phrases, and other things.

		 +----------------MV-----------+
		 +------MV-----+               |
		 +-MV--+       |               |
		 |     |       |               |
	The dog ran quickly through the park with a bone

Any number of prepositional phrases or adverbs may attach to a
verb. 

     Contents
     1. @MV+ on verbs
     2. Other @MV+ connectors on verbs
     3. @MV+ on adjectives
     4. Words taking MV-: Adverbs and prepositions
     5. Other uses of MVp and MVs
     6. MVi
     7. MVl
     8. MVx
     9. Special purpose MV connectors
     10. Comparatives I: Introduction
     11. Comparatives II: Construction of "More" phrases
     12. Comparatives III: Construction of "Than" phrases
     13. Comparatives IV: Constrained "Than" phrases
     14. Comparatives V: Constrained uses with separate clauses
     15. Comparatives VI: Comparatives involving adjectival 
            clausal complements
     16. Comparatives VII: Comparatives with "As"
     17. Comparatives VIII: False positives

@MV+ on Verbs
The way @MV+ connectors are combined with complement connectors
on verbs is quite complex. Simple intransitive, transitive and
optionally-transitive verbs simply have an optional "@MV+".
With transitive and optionally-transitive verbs, this is
conjoined with the O+ connector:

	destroy: (Sp- or I-) & (O+ or B-) & {@MV+};

Normally, prepositional phrases and the like follow the object
in this situation, as is enforced by this expression.
Sometimes, however, a prepositional phrase is inserted before
the object: "We destroyed the garage with axes on Tuesday",
"?We destroyed with axes on Tuesday the garage".  See "MV:
Other @MV+ connectors on verbs" below.

MV+ is always optional; in general verbs do not require
adverbial or prepositional modifiers. (There are a few
exceptions, like "put", which do require a prepositional
phrase; for this, Pp is used. See "Pp".) 

Some verbs connect to other verbs - modals (which take
I+), auxiliaries (which take I+, PP+, or Pg+) or verbs that
take infinitival complements (TO+). Such verbs may NEVER
make an @MV+ connection beyond the verb they attach to.
Thus in the sentence below, "in London" can connect only to
"run", not to "would", "prefer", "be" or "appointed".
             
                                            +---------MV---+
            +-PP--+-TO--+-I+--Pv--+-TO--+-I-+              |
            |     |     |  |      |     |   |              |
     1. He had expected to be appointed to run the project in London

Consider the following simplified expressions:

	expect: ...(({@MV+} & TO+) or ((O+ or B-) & {@MV+}));
	appointed: ...{@MV+} & {TO+};

"Expect" has an @MV+ conjoined with TO+, but it must connect
before the complement; this is explained below.  Note that,
since "expect" is also an ordinary transitive verb ("I
expected the appointment"), it has an @MV+ conjoined with its
O+ connector (which, again, connects beyond the direct
object), but this is disjoined with the TO+. With "appointed",
the @MV+ conjoined with the TO+ is, again, before the TO+.
Notice that the TO+ is optional here: thus "appointed" may be
used with no complement at all, in which case it may take an
MV connection ("He was appointed in London").

The same applies to complement connectors like TH+, TS+, and
C+ (attaching to clauses, regular or subjunctive), and
QI+ (attaching to indirect questions). Again, such verbs
cannot make MV connections beyond their complements. Thus the
sentence below receives only the parse shown.

                                              +---TOo-+
    +-S-+-TH-+-C-+-S---+--QI--+---C-+-S--+-I--+-O-+   +-I+MV+
    |   |    |   |     |      |     |    |    |   |   |  |  | 
2. He said that he wondered where Jane would ask him to go on Monday

Notice that phrasal complements of this kind, since they
necessarily contain verbs, will themselves have available @MV+
connectors at the end.

The point is that on any single verb expression, or in any
clause involving verb-attached embedded clauses (not
subordinate clauses and relative clauses), adverbial and
prepositional modifiers placed at the end can only attach to
the final verb in the expression. However, linkage logic
insures that every verb expression or subordinate clause will
eventually end with a verb that does not connect to a
further verb or clause, and thus will have an available
@MV+.  By doing it this way, we greatly reduce the number of
linkages that would be found on long sentences; and in most
cases the modifier applies to the final verb anyway. (Although
not always. In ex. 2 above, for example, "on Monday" seems to
apply to "go", but might also apply to "ask" or "wonder".)

In other cases, such as relative clauses, there may be
more than one MV+ available for an MV- to attach to: "I saw
the man you met on Tuesday", on Tuesday may attach to "saw" on
"met". For that matter, prepositional phrases may of course
attach to nouns as well (using M). In long sentences, therefore,
there are often many ways for prepositional phrases to attach.
If there are many prepositional phrases in the sentence as well,
the number of linkages may be very large.

Other @MV+ connectors on Verbs
In most cases, with complex verb expressions or verb-linked
subordinate-clause expressions, prepositional phrases and the
like occur at the end.  However, they may also in some cases
occur in the middle. Verbs that take complements such as TO+,
Pg+ or I+ occasionally take prepositional phrases before the
complement. And verbs that take clausal complements (TH+, C+
or QI+) sometimes take prepositional phrases before their
complements also.  Some of these uses are rather questionable
(TH+ and TO+ are best; Pg+, I+, QI+, and C+ are more
doubtful), but for now we allow them all.

              +---------------------+
              +--MV---+             |
              |       |             |
	He attempted for many years to be a concert pianist
	?We discussed at that time hiring a new secretary
	He announced  on Monday    that he was hiring Smith
	I   asked him on Tuesday    who had been hired

As mentioned, transitive verbs have "@MV+" connectors
following their "O+" connectors. However, one occasionally
sees a prepositional phrase inserted before the object:

	We destroyed with axes the garage that our grandfather 
		had built

We therefore give transitive verbs an optional "@MV+" before
the "O+", in addition to the one following. Since this
construction is rare, we give it a cost of 2.  Moreover: in
such cases, the object phrase is never a pronoun; it is always
a full noun phrase. ("*We destroyed with axes it"). We already
have a special O+ subscript, O*n+, that can be used only with
noun phrases, not with pronouns (see "K" for an explanation).
Thus we use that here as well. This yields the following:

	destroy: ([[@MV+ & O*n+]] or O- or B+) & {@MV+};

A final case to be considered is verbs that take an object
plus some other complement. Some verbs take "O+ & TOo+" (for
object+infinitive constructions), "O+ & TH+" (for
object+clause constructions), and the like. In such cases, one
never sees a prepositional phrase inserted before the
object. One occasionally sees it inserted after the object and
before the TH+ or TOo+.

	*I told on Tuesday Jane to do it
	I told Jane on Tuesday to do it

Such verbs therefore have

	(O+ or B-) & {@MV+} & {TOo+ or TH+...};

The same applies to verbs that take two objects; a prepositional
phrase may be inserted between the two objects, but never before
the first object:

	I gave him on Tuesday an expensive present
	*I gave on Tuesday him an expensive present

In cases where the verb may take two objects, we must also
prevent the second object from being a pronoun (see "O"); 
and in any case where the preposition precedes an object, 
we must prevent that object from being a pronoun (see above). 
In such	cases we use O*n+, which may not connect with pronouns.
This yields:

	gave: ... & ((O+ & O*n+) or O+ or (O+ & [[@MV+]] & O*n+) or
	([[@MV+]] & O*n+))

This can be somewhat condensed into the following:

	gave: ... & ((O+ & {{[[@MV+]]} & O*n+} or [[@MV+ & O*n+]]);

This then yields the following judgments:

	I gave my brother an expensive present
	I gave him an expensive present
	I gave an expensive present
	I gave it
	*I gave my brother it
	I gave him for his birthday an expensive present 
		(cost 2)
	I gave my brother for his birthday an expensive present
		(cost 2)
	*I gave him for his birthday it
	I gave for his birthday an expensive present (cost 2)
	*I gave for his birthday it
	*I gave for his birthday him an expensive present
	*I gave for his birthday my brother an expensive present
	*I gave for his birthday my brother it		

@MV+ on adjectives
MV is also used to attach modifying phrases to adjectives.
This is only allowed when the adjective is being used
predicatively: "He is HAPPY ABOUT his job", "*He is a happy
about his job man". As with verbs, "@MV+" is optionally
conjoined with complement connectors like "TO+" and "TH+" on
adjectives, and is to the left of the complement connectors.
Thus when adjectives participate in long phrases like "He
wants to be certain that Jane is eager to go", the "@MV+"
on "certain" and "eager" cannot be used.

Words taking MV-: adverbs and prepositions
If a word or expression has an "MV-", that means it can modify
a verb that precedes it. A number of different subscripts are
used to identify different kinds of modifiers.  For the most
part, these subscripts distinctions are just provided for the
sake of clarity. They are rarely used to constrain linkages,
although a few subscripts have special properties either in
post-processing or at the linkage level.

MVa connects adverbs and to verbs; adverbs thus have "MVa-"
connectors. Many adverbs can take optional commas; they thus
carry "{Xc+ & Xd-} & MVa-" (see "X"). Some "clausal" adverbs
can only be used in this position with commas:

	*He is angry apparently.
	He is angry, apparently.

These adverbs thus carry "Xc+ & Xd- & MVa-". 

MVp connects prepositions to verbs; prepositions have "(MVp-
or Mp- or Pp-) & J+" (The J+ connects to the prepositional
object; the Mp- is used when the preposition modifies a noun;
the Pp- is used when the prepositional phrase is a complement
of "be").

For the most part, prepositions and adverbs form clearly
distinct natural kinds.  Prepositions take an object, can
modify nouns, and can be complements of "be"; adverbs differ
in all these respects. But there are many words and phrases
which are like adverbs in some ways, but like prepositions in
others. "Alone", "everywhere" and "downtown" take no object,
but can	be complements of "be" and can modify nouns; "backwards" 
and "somewhere" take no object and cannot modify nouns, but can 
be "be"-complements. In any case, whether something is labeled
MVp or MVa has few practical consequences.

It will be noted that we do not distinguish between the many
kinds of prepositional phrases: time expressions ("on Monday"),
place expressions ("in the plane"), manner expressions ("with
skill and discretion"), special verb- or adjective- 
complement expressions ("She prepared for the meeting", "She is
angry about the decision"). There seems to be no reason to make
these distinctions for our purposes. One problem is that there
are certain verbs which seem to require a certain prepositional
complement: "He hoped for an agreement", "*He hoped on Tuesday",
"*He hoped". We could solve this problem by creating special
connectors for such prepositions; at present, we simply give
such verbs optional "@MV+" connectors, thus allowing 
questionable sentences like the ones above.
	
MVs- is used for certain conjunctions (i.e. words that can
take clauses), such as "while", "because", and "now_that". Note
that some conjunctions, such as "after", can take either objects or
clauses as complements; we usually treat these as prepositions,
giving them "MVp". Note also that coordinating conjunctions like
"although" or "but", which seem to connect two equal phrases,
take "CC-", not "MVs-"; thus they connect to the subject of the
preceding clause, not the main verb. This is because such 
conjunctions may not be used in relative clauses (unlike other
conjunctions and prepositions, which may be so used):

	The woman you said you liked on Tuesday is here
	The woman we saw after we left the party is here
	*The woman you said you liked but she was too intelligent is
		here

See "W: Coordinating Conjunctions" for further explanation.	

Other uses of MVp and MVs 
As well as taking noun-phrases (using J+) and clauses (using
C+), some prepositions and conjunctions may take present
participles, passive participles or indirect questions:

             +----MV-----+-Mg-+
             |           |    |
	I yelled at her for going to the party

              +--MV-+-Mv-+
              |     |    |
	She cried when asked about it

             +-MV--+-QI-+
             |     |    |
	I talked about how to use the program		

Such words have "(J+ or Mg+ or Mv+ [as appropriate]) & MVp-".
Some such uses are extremely unconstrained: almost any sentence
can take a phrase like "by _ing" or "after _ing". Others are
much more constrained, like "for _ing" ("*I went to the store
for getting some milk"), and most indirect question uses ("*I went
to the store about how to use the program"). At present we have
no way of controlling this. 

Note that when participles are used with conjunctions, we use
Mv and Mg rather than Pv and Pg. See "M: Mv and Mg used on
conjunctions".

MVi
MVi is used to connect infinitival phrases to verbs and
adjectives when they mean "in order to": "He went to the store
to get some bread". Thus "to" carries "(MVi- or TO-...) &
I+". (TO is used when infinitival phrases act as verb or
adjective complements: "He wanted/expected/was eager to go.")
Any verb or adjective may take such a phrase; it has a cost of
1, however. 

MVl
A few adverbs can modify prepositional phrases, conjunctions
and adverbs: "partly", "even", "largely". Notice that these
adverbs do not simply modify the previous clause: they
require a following phrase.

            +---MVl--+-MVp-+
            |        |     |
	He did it largely in his spare time
	He did it largely voluntarily
	He did it largely because he wanted to do it
	*He did it largely

Such adverbs take "MVl- & (MVp+ or MVa+ or MVs+)". Somewhat
counterintuitively, then, the prepositional phrase connects
to the rest of the sentence through the adverb; it no
longer makes a direct connection. (Notice the subscripts here
prevent such adverbs from linking in sequence: "*He did it
largely partly in his spare time".)

MVx
MVx is used to connect verbs to certain modifying phrases
surrounded by commas.  These include some kinds of phrases,
namely passive and progressive participle phrases, that must
be surrounded by commas when they modify verbs (exx. 1-4
below).

              +---MVx--+
              |   +-Xc-+-------Xd------+
              |   |    |               |               
1.	John left , carrying a dog   /////
2.	John left , followed by Bill /////		
3.	*John left carrying the dog
4.	*John left followed by Bill

5.	John left ,   with the dog   /////
	
              +---MVp---+
              |         |
6.	John left     with the dog

MVx is also used with prepositional phrases, which need not be
surrounded by commas (see exx. 5-6 above).  When they are not,
however, they use MVp to connect to the verb, not MVx.
Prepositions therefore have

with:	J+ & (MVp- or Mp- or Pp- or (Xc+ & Xd- & (MVx- or MX-));

To connect to the commas, Xc and Xd are used; see "X: comma 
phrases".

The MVx- on passive and progressive participles is disjoined
with with their normal left-pointing connectors (Pg- & Mg- for
progressives, Pv- & Mv- for passives). However, the MVx- on
participles must be to the right of the complement connectors
on the expression; the P- and M- connectors must be to the
left. Therefore the MVx- connectors on participles must be
fully disjoined with the P- and M- connectors.  In this respect
MVx- is much like MX*p- and COp+; see "CO: Participles as
Openers" for more explanation.

Special Purpose MV connectors
A number of MV connector types are used to trigger
post-processing constraints.

Various MV subscripts are used in comparatives. See the sections
below on comparatives: Sections I (MVm), II (MVt), III (MVpa,
MVpc), V (MVto, MVta, MVtp), VI (MVti), VII (MVzo).

MVh is used to attach the word "that" to verbs, in "so...that"
"such...that" constructions: "He was so angry that he left",
"She was such a good programmer that they had to keep her."
These uses of "so" and "such" are specially subscripted with
"k" (EAxk, EExk, Dm#k, Ds#k).  Post-processing ensures that
MVh is only used when a special "so" or "such" link-type is
present. (See "EAxk: so...that".) In addition, MVh carries a
cost of 2 even in its accepted usages.

The only use of subscripts to actually constrain linkages
(with the exception of the post-processing features described
above) is as follows.  There are certain uses where only a
prepositional phrase may be used. Certain prepositions seems
to take other prepositions as objects. They cannot take any
kind of adverb as objects, though.

             +-MVp-+MVp+MVp+
	     |     |   |   |
We were drinking  over out by the lake
*We were drinking over
*We were drinking over happily

Such prepositions therefore carry MVp+ as a possible
right-branching connector along with J+, Mg+, etc..

Comparatives I: Introduction 
This is perhaps a good place to describe the system's handling
of comparatives. Comparatives are constructions involving
"more...than", or "as...as". Each comparative construction has
two sides: a first half (involving "more" or "as") and a
second half (involving "than" or "as"). (The two different
"as"'s are given different entries in the dictionary, labeled
"as.y" and "as.z", and we shall refer to them that way here.)
We will begin by describing the "more...than" case; the
"as...as" case is quite similar, though somewhat simpler.

A wide variety of constructions are possible on both halves of
a comparative expression.

1.He is more intelligent  THAN	John		all
2.He is bigger			John is   	1,2
3.He runs more quickly		John does       all except 1,2,11
4.I have more CDs		is John         1,2
5.He earns more money		does Fred       all except 1,2,11
6.He plays with more skill	for money	all
7.More people attended the partyhe was last year1,2
8.He earns more			last year       all
9.He did it for more		attractive	1
10.He plays more for pleasure	Fred earns      4,5,6,7,8,10
11.He is more a scholar		came to the concert 4,5,6,7,8,10
12.He plays football more 	I work          3,12
				you have tapes  3,4,12
				elegantly       3,9
				he said he earns 4,5,6,7,8,10
				he said he was  1,2
				I had expected  all
				had been expected all
				expected        all

It seems that there is tremendous freedom in the way "more" 
phrases and "than" phrases can be formed. However, there are
strong constraints on the way they may be combined. By each
"than" phrase above are listed the possible "more" phrases that they
may be combined with. These constraints are not easy to enforce
for our system through ordinary link logic. Nor are they easy
to enforce with simple post-processing logic; very often the
"than" phrase is in an embedded clause (as in several of
the examples above), and therefore not in the same group as the
"more" phrase. Therefore, our enforcement of these rules relies
on a rather elaborate combination of link logic and post-processing.
First we will describe the construction of "more" phrases; 
then we will turn to the more complex construction of "than" 
phrases.

Comparatives II: The Construction of "More" Phrases
In the "more" phrases above, the word "more" is usually
serving a pretty clear function. In the first case above, "He
is more intelligent...", for example, it is serving as an
adjectival adverb. This is clear because it may not be
combined with another such adverb: *"He is more very
intelligent". Thus we give it specially subscripted "EA+"
connector:

            +---Pa------+
         +S-+   +---EAm-+
         |  |   |       |
	He is more intelligent than...

The other uses of "more" are similar; in each case, it is simply
acting like a determiner, noun phrase (object or prepositional
object), or adverb, and can simply link to the rest of the 
sentence as if it were a normal member of these categories.
In each case, however, the connector is specially subscripted
(solely for post-processing purposes; this will be explained
below).

He is more intelligent		EAm+
He runs more quickly		EEm+
I have more CDs			Dm*m+			    
He earns more money		Dm*m+			    
He plays with more skill	Dm*m+			    
More people attended the party	Dm*m+
He earns more			Om-			    
He did it for more		Jm-
He does it more for pleasure	MVm-			    
He is more a scholar		EB*m-

A few other words can also perform the function of "more",
marking a phrase as the left half of a comparative. These
include adjectives such as "bigger" and adverbs such as
"better" and "further". Again, in other respects these
words are just like others in the same category. Therefore
we give them ordinary adjective or adverb expressions but
with special subscripts.

He is taller 	          Pam+
He is a taller man	  Am+
A man taller than him 
  would be hard to find   Mam+
He plays better		  MVm+
How much better is it     AFm+

Finally, the words "less" and "fewer" are very similar in
function to "more", and have the same connectors. "Less"
is identical to "more" in functioning as an adverb, mass
noun phrase, and mass determiner; "fewer" duplicates the
functions of "more" as a plural noun phrase and plural
determiner.

A final kind of more phrase is one inserted as a comm phrase
modifying a noun:

          +-MX-+-MVt+
          |    |    |
	Dogs, more than I expected, were there

In general, MX is used for attaching noun modifiers to 
nouns in this way. For this purpose, therefore, we use "MX#m".
(MX#m- must be conjoined with MVt on "more", to allow a way
for the "than" phrase to attach.) 

Comparatives III: The Construction of "Than" Phrases 
The connection of "than" to the rest of the sentence is
simple; it has an MVt- connector, and thus connects to the
main verb of the sentence like a prepositional phrase. MVt is
restricted by post-processing; it cannot occur unless one of
the "more" link-types listed above appears.  This prevents
"than" phrases from occurring in non-comparative contexts (*He
is intelligent than me), and also in "as" contexts (*He is as
intelligent than me).

Now, how do we construct "than" phrases, and how do we enforce
the constraints between "than" phrases and "more" phrases?  It
is useful here to distinguish between two types of "than"
phrase.  Some types are "unconstrained"; others are
"constrained". We will discuss the unconstrained ones first.

With some "than" phrases, there seems to be almost no limits on
the kind of "more" phrases they can be combined with. One such
type is noun phrases. 

	He (is more intelligent) (runs more quickly) (earns more)
		than John

It seems here that such a complement can be used with any
kind of "more" phrase. Therefore we give "than" an O*c+
connector. No post-processing is needed here; we have already
required that some kind of "more" phrase must be used
every time "MVt" is used. So far, then we have

	than: MVt- & (O*c+...)
			
Another kind of "unconstrained" use of "than" is with a
prepositional phrase.  Again, it seems that any use of "more"
is possible:

He (is more intelligent) (runs more quickly) (earns more)
	than in the past

Thus we give "than" an Mpc+, allowing it to connect to any
prepositional phrase. Finally, "than" may take a phrase
like "was expected", or "I had expected", combined with
any use of "more":

He (is more intelligent) (runs more quickly) (earns more)
	than (I had expected) (was expected)

For this, "than" is given an Zc+ connector. Verbs like
"expect" have Z-, disjoined with their other complement
connectors. (Z is also used in subordinate "as"-phrases
like "He left, as I expected". See "Z".)

	expect: (S-...) & (TH+ or TO+ or Z-)		
							    
This yields
		       +----Z----+
		       |   +--S--+
	               |   |     |                		
	He earns more than I expected			

The second case, "He earns more than was expected", is more
problematic, and requires a further SFsic+ connector on
"than". See "Z" for more explanation.

Comparatives IV: Constrained "Than" Phrases
Other "than" phrases are more constrained. These divide into	
two groups: those where the "than" phrase contains a clause,
and those where it does not. Regarding the latter case, 
a "than" phrase may contain an adjective, but only if the
"more" phrase contains a predicative adjective as well as
the adverb "more". "Than" is therefore given Pafc+.

           +-----Pa-----+
	   +EB*m+       |        +---Pafc-+
	   |    |       |        |        |
	He is more intelligent than attractive

	*He has more money than attractive
	*He is smarter than attractive
	*More intelligent people came than attractive

The "than" phrase may contain an adverb or prepositional
phrase, but only if the "more" phrase also does, with "more"
acting as an adverb.  Thus we give "than" MV*c+.

	     +--MVp/a--+
             +-MVm+    |         +-MVp/ac+
	     |    |    |         |       |
	He plays more for money than    for pleasure
	He plays more quickly   than    elegantly

	*He has more CDs than elegantly
	?He has more CDs than for pleasure

(The last sentence is perhaps valid if "for pleasure" is being
construed in an unconstrained sense: "He has more CDs than he
does for pleasure". And we allow this.)  Finally, the "than"
phrase can be a mass or plural noun phrase, but only when
"more" is acting as a determiner. In this case, the "than"
seems to fulfill both the determiner and the main demand of
the noun; therefore we use the "U-" connector on nouns, which
overrides both these demands.

                +-Dmum+     +U*c+
                |     |     |   |
	He has more money than time
	?He has more money than a hobby

(Here again, an unconstrained interpretation is possible--and
is allowed--with both sentences.) How do we prevent these
constrained "than" uses from being mixed and matched: *"He
plays more quickly than intelligent", *"He is more intelligent
than quickly"?  In each case, the particular words that are
needed in the "more" phrase, and the particular use of "more",
can be identified by their link-names.  Therefore, we can
simply insist in post-processing that each "than" link-type
may only be used with the appropriate "more" link-types.
Thus, "Pafc" demands "Pa" as well as "EB#m"; "MVpc" and "MVac"
demand either "MVp" or "MVa"; and"U#c" demands "Dm#m".

A "than" phrase can also contain a subjectless clause:

	1.More people attended the party than came to the concert
	2.More money was committed than was available
	3.*More money was committed than were available

To handle this, we give "than" an S**c+ connector. No new
domain is started here. For this usage, "more" must either be
serving as a noun-phrase (as in 1 above), or as determiner of
a noun (as in 2); and in the latter case, the verb of the
"than" clause must agree in number with this noun (see 3
above). The number of the noun in the "more" phrase is
indicated by the D link; if it is a "Dmum", the noun is
singular, whereas if it is "Dmcm", the noun is plural.  If the
"than" connects to a singular verb (as in 1), a Ss*c will be
formed. In post-processing, Ss#c demands an Om, Jm, or Dmum;
an Sp#c demands an Om, Jm, or Dmcm. In this way we enforce
number agreement.

So far, then, we have:

than: MVt- & (O*c+ or Mpc+ or ({SFsic+} & Zc+) or S**c+ or
U*c+ or Pafc+)

Comparatives V: Constrained Uses with Separate Clauses
In all the constrained cases discussed so far, the "more"
phrase and the "than" phrase are in the same post-processing
group. This seems logical, since groups usually correspond to
clauses, and in these cases both phrases seem to be in the
same clause. Indeed, it is necessary for both phrases to be in
the same group for the post-processing rules to work. In other
cases, however, the "than" phrase seems to contain its own
clause.

1.	He is more intelligent than I am
2.	He earns more than I earn
3.	I run more quickly than he does
4.	*He is more intelligent than I do
5.	*He earns more than I am
6.	*He runs more quickly than I earn

In the first case, we can use the AF- connector on verbs like
"be" and "seem" which take adjective complements (used also in
adjectival questions: "how intelligent is he?"). In the second
case, we can use the B- connector on verbs, used with fronted
objects in questions and relatives ("What do you earn?").  In
the third case, we need to create a special connector.
Normally, auxiliary verbs and modals like "do" and "can"
require a main verb: "*I do", "*I can". In this case, however,
the comparative seems to satisfy this need. Therefore, we give
auxiliaries "CX-" disjoined with their main verb (I+ or PP+)
connectors.  This yields the following linkages:

				 +--AF-+
		                 |     |
	He is more intelligent than  I am

				 +--B--+
		                 |     |
	He earns more money    than I earn

				 +--CX-+
		                 |     |
	He runs more quickly   than  I do

So far, then, "than" has the following:

than: MVt- & (O*c+ or Mpc+ or ({SFsic+} & Zc+) or S**c+ or
U*c+ or Pafc+ or AFd- or Bc- or CX-)

These "than" phrases are clearly constrained, as shown by
sentences 3-6 above. But in order to enforce these constraints
as we do in the earlier cases, the "than" phrase and the
"more" phrase have to be in the same group. Since normally
groups correspond to clauses, it is not at all clear that the
two phrases would be in the same group in these cases.  In
simple cases such as the ones above we could perhaps prevent a
new domain from being started at the "than" phrase.  However,
in other cases, the "than" phrase may include an embedded
clause: "He is smarter than I think he is".  Normally, the C+
on "think" would start a new domain in this case.  But if that
happens, how do we enforce post-processing constraints between
the "more" phrase and the "than" phrase?

Consider the following structure:

             +-------MVto----+
             +------O---+    +--Bc(e)-+
             |    +Dmum-+    |   +S(e)+
             |    |     |    |   |    |
	He earns more money than I  earn

Notice first of all that the "than" is making an "MVto"
connection to the left, rather than the "MVt" described
earlier. This link-type starts an 's' domain, which contains
the whole "than" phrase. (The "Bc" is a restricted link, as
are the AFd and CX links described above; this prevents the
subordinate group from spreading back to the rest of the
sentence.) What we want to do is enforce a constraint on the
"B" link. The "Bc" link may only be used if a "Dm#m" is
present in the "more" phrase (or one of several other links:
Om, Jm, or MX#m). The "Bc" link and the "Dm#m" are not in the
same group, so this cannot be enforced directly. Note,
however, that the "Bc" connects to "than", which is making the
"MVto" connection, and this MVto is in the same group as the
"Dm#m". Therefore, we can use ordinary link logic to ensure
that the Bc only occurs with MVto:

than: (MVt- & (O*c+ or Mpc+ or...)) or (MVto- & Bc+);

and we can then use post-processing to ensure that MVto only
occurs when a Dm#m (or some other compatible link-type) is
present in the same group.  In effect, then, we use link logic
to communicate a post-processing constraint from one group to
another.

A similar process is used with the CX and AF cases. CX
requires a determiner, noun-phrase, or adverb use of "more";
AF requires a adjectival-adverb use (or a comparative
adjective like "bigger" or "better"). CX+ and AF+ on "than"
are each conjoined with a special form of "MVt" (MVtp and
MVta, respectively). In both cases a new group is started for
the "than" phrase; but in both cases, the "MVt#" is in the
outer group, thus its use (and indirectly the use of the CX
and AF) can be constrained depending on the links present in
the "more" phrase. (The exact constraints involved here are
quite complex. Basically, an AF in the "than" phrase requires
some kind of adjective-related "more" link like Pam or Am; a
CX in the "than" phrase is compatible with many different
"more" links.) By doing this, we can handle not only
simple cases like those above, but also more complex cases
where the "than" phrase is in an embedded clause, like "He
earns more money than I thought he did".

In cases where the than-phrase contains "be" or an auxiliary,
subject-verb inversion may occur:

	He is more intelligent than am I
	He runs more quickly than do I

To allow the first of these, we give "than" a "PF+" connector.
Forms of "be" have PF-; this is used in certain cases where
the complement demand of "be" is fulfilled by something
preceding.  To handle the second, we give auxiliaries "CQ-"
connectors, conjoined with their SI+ connectors (unlike CX-,
which is conjoined with their S- connectors). Auxiliaries thus
have:

	do: (S- & (I+ or CX-...)) or (SI- & (I+ & CQ-))

(Since both CQ and PF occur with s/v-inversion, they
must be added to the "compatible with inversion" and
"requires inversion" lists in post-processing; see "SI:
Questions requiring s-v inversion".)

In terms of the constraints on their use, the PF case is
identical to the AF case described above; the CQ case is
identical to the CX case.  We already have a system in place
for enforcing the right constraints for AFd and CX; thus PF
and CQ can simply be disjoined with them. This yields:

than: ... or (MVta- & (AFd+ or PF+)) or (MVtp- & (CX+ or CQ+))

One more case of than-phrases in a separate clause is easy to
deal with. A "than" phrase may contain a complete clause:

                +--EEc-+     +-Cc-+
		|      |     |    |
	I ran more quickly than  he painted his house
	
This usage is constrained: the "more" phrase must must be
acting either as an adverbial-adverb or a verb adverb ("I ran
more").  In such a case, it is most logical to give "than" a
C+ connector. C links are not (normally) in the domains they
start; thus the Cc here is in the same group as the "more"
phrase, and the constraints can be easily enforced.

_Comparatives VI: Comparatives Involving Adjectival Clausal
Complements_
A special kind of comparative involves a "more" phrase with
an adjective plus its complement; the "than" phrase then
includes a similar complement, a similar main clause, or both:

I am more confident that Joe will come than I am that Fred will go
                   			    that Fred will go
					    I was
It is more likely that Joe will come than it is that Fred will go
					  that Fred will go
				          it was
*					  Fred is that Joe will go

So far, we have made no provision for "than" phrases to take
such complements at all. We have dealt with the case of
more-phrases containing adjectives: "He is more intelligent
than I am". As described above, an AFd+ connector on "than" is
used for attaching to the verb of the "than" phrase; this is
conjoined with a MVta-. We now add complement connectors like
those on adjectives: THc+, TOic+, and TOfc+. Either the "be"
phrase may occur, or the complement phrase, or both. This then
yields:

than: ... or (MVta- & (AFd- or ({AFd-} & (THc+ or TOic+ or TOfc+))));

We have already enforced that the MVta will only occur when
the "more" phrase contains an adjective modified with "more".
Various other constraints must be enforced here. If the
subject of the first phrase is filler "it" (that is, if there
is a adjective-complement phrase present that can only be used
with "it"), then the subject of the second phrase must be as
well.  Therefore, we add the complex MVti- & AFdi+. This works
the same way as the MVta complex, except that MVti is only
allowed with filler-it, while the MVta is only allowed with
ordinary subjects. Thus we prevent the final incorrect
sentence above. This yields:

than: ... or (MVta- & AFd+) or (MVti- & AFdi+) or 
((MVta- & {AFd+}) or (MVti- & {AFdi+}) & (THc+ or TOic+ or 
	TOfc+ or (TOt+ & B+)))

However, there is a problem here. Normally, in order to
enforce these constraints, the MVta must be in the same
group as the "more" phrase. But when an adjective takes
a complement such as TOi or TH, the complement usually
starts a new group:

    +----Pa---+                ?--MV--+
 +SF+   +--EAc+-TH-+--C-+S(e)+        | 
 |  |   |     |    |    |    |        |
It is more likely that Jane left    than it is that...

and there is no way for anything to the right to make an
MV connection back to the outer group. Thus, in the sentence
above, there is no way for the MVta to be in the same group
as the outer group of the "more" phrase. 

To fix this, we give adjectives "LE+" connectors, disjoined
with their complement connectors (if any). "Than" can then
either make an LE link to the adjective of the "more" phrase
(if it is taking a complement) or an MVta (if it is not).
The sentence above therefore gets the following linkages:

    +----Pa---+----------LE-----------+--AF--+
 +SF+   +--EAc+-TH-+--C-+S(e)+        |      |
 |  |   |     |    |    |    |        |      |
It is more likely that Jane left    than it is that...

Now the LE link is in the same group as the "more"
phrase. So it takes the place of the MVta, enforcing the same
constraints: the "more" phrase must contain an EAc, and if the
"more" phrase contains a filler-it subject, the "than" phrase
must also.

A further constraint is that when the "than" phrase contains
a complement, it must be of the same kind as that in the
"more" phrase: 

*It is more important to go than it is that Fred goes. (TO/TH)
*It is more important that Fred goes than to stay. (TH/TO)
*It is more pleasant to use than it is to go. (TOt/TOi)

To enforce this, The complement connectors on "than" are given
special subscripts; post-processing insists that these
link-types are only used when the corresponding link occurs in
the same group. (For this to work, the complement link-type of
the "than" phrase must be in the same group as that of the
"more" phrase. However, we want the "AFd" to be in a different
group. Thus, rather than having the MVta or LE link start the
group as we do with MVto and MVtp, we have the AFd link here
start the group.) This yields the following structure:

                                  +----THc----+  
    +----Pa---+---------LE--------+-AF(e)+    |
 +SF+   +--EAc+-TH-+--C-+S(e)+    |   +SF+    |
 |  |   |     |    |    |    |    |   |  |    |
It is more likely that Jane left than it is that...

Comparatives VII: Comparatives with "As" 
Comparatives with "as" are quite similar to those with
"more...  than", only somewhat simpler. The word "as"
corresponds to "more"; a different word "as", as it were,
corresponds to the word "than". These two "as"'s are called
"as.y" and "as.z", respectively.

It was mentioned that "than" connects to the rest of the
sentence using a subscripted MV- connector (or rather one of
several: MVt, MVto, MVta, MVtp, MVti).  Post-processing
carries a list of all the link-types that occur with "more":
EAm, EEm, Dm#m, etc.. If none of these links are present, then
no "more" phrase has occurred, so no "than" phrase may occur
either: the MVt links may not be used. Note that a "than"
phrase can not be used with an "as" phrase, nor vice versa:

	*He earn as much money than she earns
	*He earns more money as she earns

Thus "as.y" connectors must be subscripted differently from
"more" connectors. Once this is done, we can make a separate
list of "as.y" connectors; we then give "as.z" "MVz"
subscripts. We can then ensure that these subscripts are used
only with the "as.y" connectors, and the "than" subscripts are
used only with "more" connectors.

Many of the same connectors occur with "as.y" as occur with
"more". With adjectives and adverbs, "as.y" serves as an
adverb, exactly as "more" does:

He is as smart		EAy+
He runs as quickly	EEy+

In other cases, "as.y" must connect with "much" or "many" to
serve the same function as "more". When acting as a verb
adverb, a noun phrase, or a mass determiner, it must attach
to "much". When acting as plural determiner, it must attach
to "many". This uses the "AM" connector. "Much" and "many"
have "AM-":

much: AM- & (Dmuy+ or Oy+ or Jy+ or MVy-);
many: (AM- & Dmcy+);

    +-----O------+             +---Oy---+          +---MVy-+
    |  +-AM-+Dmuy+             |    +-AM+          |   +AM-+
    |  |    |    |             |    |   |          |   |   |
I have as much money	    I earn as much	I walk as much

Notice that it is then "much" (or "many") that makes the
specially subscripted O, J, MV and D connections that will be
used in post-processing.

The expression for "as.z" is very similar to that for "than".
It was mentioned that different subscripts are used for the
MV- connecting "as" to the left. Beyond this, however, most of
the connectors for "as.z" phrases are exactly the same as
those for "than", and are used in the same way. For example,
"as.z" can form unconstrained phrases using "O*c+" and "Mpc+",
just like "than". It can also make constrained,
domain-starting phrases using "MVzo- & Bc+" (this is the same
as the complex on "than", except that a "z" subscript is used
instead of a "t"). With "than", post-processing ensured that
MVto was used only when certain links were present in the
"more" phrase: Dm#m, Om, Jm.  For "as.z", we simply add the
corresponding "as.y" link-types to this same list (Dmuy, Dmcy,
Oy, Jy), and we likewise make MVzo require one of the links on
the list. (There is no danger that an "as" link will be used
with a "more-than" link; we have already stipulated that an
"than" link requires a "more" link rather than an "as.y" one,
and similarly with "as.z".)

The main difference with "as...as" is that its uses are
somewhat more limited than "more...than":

	He is more intelligent than attractive
	*He is as intelligent as attractive
	He did it more quickly than carefully
	?He did it as quickly as carefully

"As" is also a preposition and conjunction, and thus can be
used in this capacity in many of the kinds of sitations where
it is used as a comparative. (For this purpose it has yet a
third dictionary entry, "as.p".) 

	Joe is coming, as (I have to leave / I expected / a surprise)

For this reason, many comparative sentences with "as" get
multiple parses, and many strange-sounding comparative
constructions will be accepted with "as" as a preposition.

Comparatives VIII: False positives
Despite our efforts, there are still some false positives that 
arise with comparatives. While the constraints on the kinds of
"than" phrases and "more" phrases that can be combined work
fairly well, there is nothing to ensure that they will be used
in the right order: the parser thus accepts, for example, "*He
ran than I did more quickly." Or one might be used in an
opener, another in the main part of the sentence: "*More
quickly, he ran than I did".

Grammar Documentation Page.