The clefted element can be of a number of categories, for example NP, PP or
adverb. The clause can also be of several types. The English XTAG grammar
currently has a separate analysis for only a subset of the `specificational'
it-clefts11.1, in particular the ones without gaps in the clause
(e.g. ((126)) and ((127))). It-clefts that have gaps in the clause, such
as ((124)) and ((125)) are currently handled as relative clauses. Although
arguments have been made against treating the clefted element and the clause as
a constituent ([#!Delahunty84!#]), the relative clause approach does capture
the restriction that the clefted element must fill the gap in the clause, and
does not require any additional trees.
In the `specificational' it-cleft without gaps in the clause, the
clefted element has the role of an adjunct with respect to the clause.
For these cases the English XTAG grammar requires additional trees.
These it-cleft trees are in separate tree families because, although
some researchers (e.g. [#!Akmajian70!#]) derived it-clefts through
movement from other sentence types, most current researchers
(e.g. [#!Delahunty84!#], [#!Knowles86!#], [#!gazdar85!#],
[#!Delin89!#] and [#!Sornicola88!#]) favor base-generation of the
various cleft sentences. Placing the it-cleft trees in their own tree
families is consistent with the current preference for base
generation, since in the XTAG English grammar, structures that would
be related by transformation in a movement-based account will appear
in the same tree family. Like the base-generated approaches, the
placement of it-clefts in separate tree families makes the claim that
there is no derivational relation between it-clefts and other sentence
The three it-cleft tree families are virtually identical except for the
category label of the clefted element. Figure 11.1 shows the
declarative tree and an inverted tree for the PP It-cleft tree family.