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In the English XTAG grammar, VP and S-modifying adverbs anchor the auxiliary trees $\beta $ARBs, $\beta $sARB, $\beta $vxARB and $\beta $ARBvx,19.5 allowing pre and post modification of S's and VP's. Besides the VP and S-modifying adverbs, the grammar includes adverbs that modify other categories. Examples of adverbs modifying an adjective, an adverb, a PP, an NP, and a determiner are shown in ((307))-((314)). (See Sections 23.1.5 and 23.4.1 for discussion of the $\beta $puARBpuvx and $\beta $spuARB, which handle pre-verbal parenthetical adverbs and post-sentential comma-separated adverbs.) XTAG has separate trees for each of the modified categories and for pre and post modification where needed. The kind of treatment given to adverbs here is very much in line with the base-generation approach proposed by [#!Ernst84!#], which assumes all positions where an adverb can occur to be base-generated, and that the semantics of the adverb specifies a range of possible positions occupied by each adverb. While the relevant semantic features of the adverbs are not currently implemented, implementation of semantic features is scheduled for future work. The trees for adverb anchored modifiers are very similar in form to the adjective anchored modifier trees. Examples of two of the basic adverb modifier trees are shown in Figure 19.10.
Figure: Adverb Trees for pre-modification of S: $\beta $ARBs (a) and post-modification of a VP: $\beta $vxARB (b)
\includegraphics[height=5in]{/mnt/linc/xtag/work/doc/tech-rept/ps/modifiers-files/}   \includegraphics[height=4.5in]{/mnt/linc/xtag/work/doc/tech-rept/ps/modifiers-files/}
(a)   (b)

Like the adjective anchored trees, these trees also have the NA constraint on the foot node to restrict the number of derivations produced for a sequence of adverbs. Features of the modified category are passed from the foot node to the root node, reflecting correctly that these types of properties are unaffected by the adjunction of an adverb. A summary of the categories modified and the position of adverbs is given in Table 19.2.
Table 19.2: Simple Adverb Anchored Modifiers
  Position with respect to item modified
Category Modified Pre Post
S $\beta $ARBs $\beta $sARB
VP $\beta $ARBvx,$\beta $puARBpuvx $\beta $vxARB
A $\beta $ARBa $\beta $aARB
PP $\beta $ARBpx $\beta $pxARB
ADV $\beta $ARBarb $\beta $arbARB
NP $\beta $ARBnx  
Det $\beta $ARBd  

In the English XTAG grammar, no traces are posited for wh-adverbs, in-line with the base-generation approach ([#!Ernst84!#]) for various positions of adverbs. Since convincing arguments have been made against traces for adjuncts of other types (e.g. [#!Baltin!#]), and since the reasons for wanting traces do not seem to apply to adjuncts, we make the general assumption in our grammar that adjuncts do not leave traces. Sentence initial wh-adverbs select the same auxiliary tree used for other sentence initial adverbs ($\beta $ARBs) with the feature <wh>=+. Under this treatment, the derived tree for the sentence How did you fall? is as in Figure (19.11), with no trace for the adverb.
Figure 19.11: Derived tree for How did you fall?

Figure: Complex adverb phrase modifier: $\beta $ARBarbs

There is one more adverb modifier tree in the grammar which is not included in Table 19.2. This tree, shown in Figure 19.12, has a complex adverb phrase and is used for wh+ two-adverb phrases that occur sentence initially, such as in sentence ((315)). Since how is the only wh+ adverb, it is the only adverb that can anchor this tree.
how quickly did Srini fix the problem ? 

Focus adverbs such as only, even, just and at least are also handled by the system. Since the syntax allows focus adverbs to appear in practically any position, these adverbs select most of the trees listed in Table 19.2. It is left up to the semantics or pragmatics to decide the correct scope for the focus adverb for a given instance. In terms of the ability of the focus adverbs to modify at different levels of a noun phrase, the focus adverbs can modify either cardinal determiners or noun-cardinal noun phrases, and cannot modify at the level of noun. The tree for adverbial modification of noun phrases is in shown Figure 19.13(a). In addition to at least, the system handles the other two-word adverbs, at most and up to, and the three-word as-as adverb constructions, where an adjective substitutes between the two occurrences of as. An example of a three-word as-as adverb is as little as. Except for the ability of at least to modify many different types of constituents as noted above, the multi-word adverbs are restricted to modifying cardinal determiners. Example sentences using the trees in Figure 19.13 are shown in ((316))-((320)).

Figure: Selected Focus and Multi-word Adverb Modifier trees: $\beta $ARBnx, $\beta $PARBd and $\beta $PaPd
\includegraphics[height=1.1in]{/mnt/linc/xtag/work/doc/tech-rept/ps/modifiers-files/}   \includegraphics[height=1.75in]{/mnt/linc/xtag/work/doc/tech-rept/ps/modifiers-files/}   \includegraphics[height=1.75in]{/mnt/linc/xtag/work/doc/tech-rept/ps/modifiers-files/}    
$\beta $ARBnx   $\beta $PaPd   $\beta $PARBd    
(a)   (b)   (c)    

The grammar also includes auxiliary trees anchored by multi-word adverbs like a little, a bit, a mite, sort of, kind of, etc.. Multi-word adverbs like sort of and kind of can pre- modify almost any non-clausal category. The only strict constraint on their occurrence is that they can't modify nouns (in which case an adjectival interpretation would obtain)19.6. The category which they scope over can be directly determined from their position, except for when they occur sentence finally in which case they are assumed to modify VP's. The complete list of auxiliary trees anchored by these adverbs are as follows: $\beta $NPax, $\beta $NPpx, $\beta $NPnx, $\beta $NPvx, $\beta $vxNP, $\beta $NParb. Selected trees are shown in Figure 19.14, and some examples are given in ((321))-((324)).
Figure: Selected Multi-word Adverb Modifier trees (for adverbs like sort of, kind of): $\beta $NPax, $\beta $NPvx, $\beta $vxNP.
\includegraphics[height=1.5in]{/mnt/linc/xtag/work/doc/tech-rept/ps/modifiers-files/}   \includegraphics[height=1.5in]{/mnt/linc/xtag/work/doc/tech-rept/ps/modifiers-files/}   \includegraphics[height=1.5in]{/mnt/linc/xtag/work/doc/tech-rept/ps/modifiers-files/}    
$\beta $NPax   $\beta $NPvx   $\beta $vxNP    
(a)   (b)   (c)    

John is sort of [AP tired]. 

John is sort of [PP to the right]. 

John could have been sort of [VP eating the cake]. 

John has been eating his cake sort of [ADV slowly]. 

There are some multi-word adverbs that are, however, not so free in their distribution. Adverbs like a little, a bit, a mite modify AP's in predicative constructions (sentences with the copula and small clauses, AP complements in sentences with raising verbs, and AP's when they are subcategorized for by certain verbs (e.g., John felt angry). They can also post-modify VP's and PP's, though not as freely as AP's19.7. Finally, they also function as downtoners for almost all adverbials19.8. Some examples are provided in ((325))-((328)).

Mickey is a little [AP tired]. 

The medicine [VP has eased John's pain] a little. 

John is a little [PP to the right]. 

John has been reading his book a little [ADV loudly]. 

Following their behavior as described above, the auxiliary trees they anchor are $\beta $DAax, $\beta $DApx, $\beta $vxDA, $\beta $DAarb, $\beta $DNax, $\beta $DNpx, $\beta $vxDN, $\beta $DNarb. Selected trees are shown in Figure 19.15).

Figure: Selected Multi-word Adverb Modifier trees (for adverbs like a little, a bit): $\beta $vxDA, $\beta $DAax, $\beta $DNpx.
\includegraphics[height=1.5in]{/mnt/linc/xtag/work/doc/tech-rept/ps/modifiers-files/}   \includegraphics[height=1.5in]{/mnt/linc/xtag/work/doc/tech-rept/ps/modifiers-files/}   \includegraphics[height=1.5in]{/mnt/linc/xtag/work/doc/tech-rept/ps/modifiers-files/}    
$\beta $vxDA   $\beta $DAax   $\beta $DNpx    
(a)   (b)   (c)    

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Next: Locative Adverbial Phrases Up: Modifiers Previous: Prepositions
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