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THE LINGUISTICS STUDENT’S HANDBOOK 38
The one place where the principle of enclosing elements in boundaries fails
to hold is with affixes. Affixes are separated from their bases by a single boundary,
but are not enclosed in boundaries. So that if we include affixal boundaries
in the phrase fine words, we get ##fine##word#s##. Sometimes this
difference is supposed to hold only with those affixes (as in the example just
cited) which might be assumed to have no word-class marking. In a language
like English this means with inflectional suffixes and with prefixes. Suffixes like
the -ness in happiness are said to have their own word class (they always create
nouns), and thus to work like words in terms of the tree structure. (See e.g.
Lieber 1992: 35-7, but contrast with Jensen 1990: 35.) This is controversial.
Before we move on to consider alternative ways of writing environments,
two more abbreviatory conventions need to be considered. The first of these is
the use of parentheses to enclose optional material. Where an item is enclosed
in parentheses at any point in the rule, the rule works equally well with or
without the parenthesised material. However, if you are applying the rule to
potential input data, you should always try to apply the rule with all the
optional elements present, and only if the rule cannot be applied that way
should you apply it without the optional elements. That is, you apply the
longest expansion first. The options presented by the use of parentheses in this
way are alternatives: if one option applies the other does not; the two options
cannot both apply. This is called disjunctive ordering. For example, the stress
in French words spoken in isolation can be stated by rule (7).
(7) V → [� stress] / ___ (C) (C) (ə) #
Given a form like /pətitə/the final /ə/ has to be seen as matching the /ə/
in (7), otherwise, if it was ignored and the rule was applied without the optional
elements first, we would get the stress on the final vowel, i.e. on the /ə/. Since
the stress in this word falls on the /i/, we need to consider the longest applicable
version first, and then stop applying the rule. Anything else will give the
wrong output.
The other abbreviatory convention to mention briefly is the rather informal
use of the asterisk after an element to show that it may be repeated. This is
found most often in syntactic rules, where a given NP may include an indefinite
number of adjectives, or where a given sentence may include an indefinite
number of prepositional phrases. A rule such as (8) illustrates both these
conventions.
(8) NP → (Num) (AP*) N (PP)
(8) states that an NP must contain an N and may also contain a number, one
or more adjective phrases and, following the noun, a prepositional phrase.