On the Creative Use of Language: the Form of 
Lexical Resources 
David D. McDonald Fedefica Busa 
14 Brantwood Road Computer Science Department 
Arlington, MA 02174, USA Brandeis University 02254, USA 
mcdonald @cs.brandeis.edu fedefica @ cs.brandeis.edu 
Abstract 
We introduce the problem of referential creativity: how it is that a person can give a word or phrase a new 
denotation even though she has never heard or used in that way before. Using real examples that we have collected, 
we focus on the case of semantic type coercion, where a phrase of a given type is used in a textual context that 
requires a completely different type yet the intended message is perfectly well understood. 
We frame our account as the problem of what form the linguistic resources available to a speaker must have such 
that she can appreciate the opportunity for creative phrasings. What systematic relationships exist in the speaker's 
lexicon that enable a phrase to convey something quite different than it normally would, and why tshould his ever 
occur during the generation process? We draw on a new theory of how information is associated with a wor6-- 
Pustejovsky's Generative Lexicon--and we embed our account in a theory of generation as an incremental process 
that makes use of a rich model of the situation in which the utterance occurs. 
Keywords: creativity, lexical choice, content determination, incremental generation 
1. The problem 
People are always saying new things. Usually the 
reason is obviohs: we continually find ourselves in new 
situations, and the differences in these situations--our 
goals, the participants, the activities, the props, the 
locations, the recent history, etc.--naturally lead to 
differences in what we say. Other cases are not so easily 
explained. Differences in the situation will not account for 
those occasions when our choice of phrasing is inconsistent 
with the selectional restrictions of its context; when we 
make a reference that on its face should not be able to 
communicate our intended meaning yet in the situation in 
which it is uttered is both natural and completely 
understood. 
Consider texts 1 and 2, which were uttered by the 
authors and transcribed immediately afterwards. Both were 
completely understood by their hearers. 
(1) "I wouM really like to have you guys over for dinner, 
so let me know whether for you it is better before or 
afier Florida." 
(2) "Just give me a few bites" 
In (1), a geographical location, Florida, provides 
information about a time interval. In (2), "a few bites (of 
food)" denotes a quantity, yet it is readily interpreted as a 
duration. 1 If hearers made their interpretations strictly 
compositionally, these would be nonsense to them. If 
speakers strictly respected selectional restrictions, they 
would never generate such sentences. What is it that 
The normal way to express the message in (2) would be 
"just give me a little while longer", meaning that the 
speaker wants to wait longer and, in this case, to eat a 
little bit more before doing something his interlocutor 
has requested. Example (I) involves an event that takes 
place in Florida. It is discussed below. 
explains this ability? What do people know about their 
language and its relationship to situations that prompts 
them to produce these apparently type-inconsistent 
utterances and while still being understood? 
We will argue in this paper that this ability follows 
from the use of a generative lexicon, one based on the 
dynamic operation of general rules that define what 
realizations are possible through interactions between the 
lexical semantics of our linguistic resources and the 
situation, rather than through the customary fixed 
enumeration of cases and decision cntera. Coupled with a 
theory of content selection as an incremental walk through 
a highly structured mental model of the speaker's 'relevant 
portion of the situation', and with an architecture for 
generation with multiple levels of (progressively more 
linguistic) representation that actively constrains what 
realizations are possible, this view of the lexicon can 
explain how speakers are led to these unusual 'creative' 
constructions and why they are understood by their hearers. 
1.1 Related phenomena 
There is every reason to believe that these two 
utterances and the others we will present later are new and 
unique. They were semantic patterns of expression that we 
had never uttered before nor ever heard anyone else say. 
Nevertheless, they are similar in kind to other turns of 
phrase that have become quite commonplace: 
(3) "Do you take Visa?" 
(4) "With encouragement from Moscow, Bosnian Serbs 
appear to be compling with the UN ultimation to 
remove their heavy weapons from Sarjevo." 
(4) is an example of a now conventional meronymic 
construction where a part of an object, here the capital city 
Moscow, is able to stand in for the whole. This is a natural 
move that is probably prompted by the salience of the 'part' 
in the speaker's mind: Moscow is, after all, the actual site 
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of the governmental decision making even though we take 
the act as being done by the Russian Republic as a whole. 
Meronomy and other kinds of metonymic substitutions 
have been extensively studied (e.g. Cruise 1986, Leher & 
Kittay 1992 and their references) our contribution will be to 
couch some aspects of these phenomena in a computational 
context. 
Example (3) comes closer to the problems of lexical 
semantics that concern us in this paper. Here the 
reconstruction that the hearer must make is not part-whole 
but based on the object's purpose--what has been called its 
'telic' role. It also reflects the 'polymorphism' that typifies 
most lexical knowledge, whereby one word, the name of the 
credit card, is able to convey both the physical aspect of the 
card as a piece of plastic and its role as a means of 
commercial exchange. Different situations will involve 
different aspects of the credit card, yet they all can be 
conveyed by the very same word. 
Similarly, the American speaker's proclivity to 'verb' 
nouns is well-known: 2 
(5) "You can Mastercard your pledge." 
(6) "I'll sprig the grapes." 
What these and other creative uses of words have in 
common is that they are only uttered in what we call 'high 
salience' situations--situations where the activity under 
discussion is completely clear to all the interlocutors and 
the interlocutors are only attending a few, mutually known, 
entities. But this class of utterances as well, however, 
follows patterns that we all appreciate as completely 
conventional, though at one time they too were new. 
(7) "Roy irons his own shirts" 
(8) "Bob vacuumed the floor without being asked" 
Here the verbs are the same word as the nouns that 
name the instruments that are prototypically used to 
perform the actions: 'iron', 'vacuum (cleaner)'. As with 
credit cards, these words are taking on a role that relies, 
polymorphically, on their telic uses as instruments for 
certain prototypical acts. 
The capability these examples illustrate is a new 
problem for research in natural language generation. It 
points to a productive capacity that people have that enables 
us to exploit our knowledge of the language to construct 
new uses for established terms, in the process providing 
shorter, more cohesive realizations for content that could 
otherwise be quite awkward to express. It is an important 
problem because it is part of the scientific problem of 
understanding what language is and how people employ it, 
and also because having an account it should aid us in the 
engineering problem of designing machine speakers by 
Example (5) was spoken by a public radio announcer 
during an on-air fund drive. (6) was spoken by one of the 
authors and referred to the operation of taking a large 
bunch of grapes and cutting it into small, hand-sized 
portions ('sprigs') as part of getting ready for a dinner 
party. 
providing insights into representations and procedures that 
will make them more natural and fluent. 
2. Referential Creativity 
Every new phenomenon needs a name, and our choice 
is "referential creativity". We call it creative because the 
speaker has never before heard or used that precise pattern of 
semantic elements and grammatical relations. The 
principles and representational structures involved are surely 
an established part of our knowledge of language, but their 
use is the application of productive principles in the face of 
a new situation, and not the instantiation of a well-trod 
template or mapping. 
Creativity is taken by many to be a central property of 
the human use of language. Chomsky (1966) introduced it 
into modern linguistics, and took the notion back to ideas 
implicit in the works of von Humbolt in the early 1800s. 
He used it to revolutionize the machinery of syntax. We 
apply it here to the process of generation, building on its 
application to lexical semantics by Pustejovsky (1991). 
We call this phenomenon referential creativity because 
in it a speaker uses a new, ostensibly type-inconsistent 
referent in a linguistic context that would normally be filled 
with a referent of a quite different type. In (1) a geographical 
entity was used instead of the end-points of an event; in (2) 
a measurement was used instead of a duration. 
The referent that is used and the one that it invokes in 
the mind of the hearer are always logically related. We can 
see this in (7), which is one of the less abbreviated ways to 
realize the content expressed in (1). 
(7) "... before you leave for your vacation in Florida or 
after you get back" 
Here the reference to Florida appears as a component unit 
within the larger events of leaving for (and returning from) 
a vacation there. The two transitional events, the end points 
of the event of taking a vacation, fit the selectional 
restrictions imposed by "before" ("after"), and so constitute 
a normal, uncreative, realization. 
Referentially creative texts are not compositional. The 
New Englander's world knowledge that one takes winter 
vacations in Florida notwithstanding, a hearer cannot 
reconstruct the intended referent of "Florida" in (1) in 
isolation from the immediately prior linguistic context. The 
meaning of the whole involves the interaction of the 
meaning of the parts and not just their sum, a phenomenon 
called co-compositionality, (Pustejovsky (1994). 
We see co-compositionality as part of the speaker's 
processing as well. At any given moment we believe there 
will typically be several units of content vying for 
expression which, while distinct, are interconnected and 
even redundant. At the point of the referentially creative 
choice in (I) these will include at least the event (the 
vacation) and its location. The choice between the two is 
not made in isolation based solely on the information they 
contain, but isstrongly influenced by the choice made just 
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before, namely to use the semi-fixed phrase "... before or 
after". The speaker's commitment to that phrasing imposes 
a contraint on what follows that interacts with the potential 
content and influences what happens. 
As the speaker looks for the next unit of content to 
select, her goal is simply to communicate the two 
moments, not to deploy any particular unit to which she 
was committed long before reaching that point in the 
utterance. Any unit that will convey the information 
directly or indirectly can be used. Such a lack of prior 
commitment is the whole point of an incremental model of 
generation, which we are now exploring at the level of 
content selection rather than just the customary level of 
realization and surface form (see Kempen & .Hoenkamp 
1987, DeSmedt 1990, McDonald 1980). 
Part of the speaker's knowledge, given the particular 
circumstances in which this actually attested utterance was 
made, is that just saying "Florida" will communicate the 
event of the vacation and through it the two time points, 
thereby achieving her communicative goal. We hold that 
this knowledge is mediated by the lexical entry for Florida, 
whose content and form follow a theory of lexical 
semantics known as the Generative Lexicon ("GL"), the 
subject of Section Five. Before going into that, however, 
we have to establish the context in which this lexical 
knowledge is deployed. 
3. Situational Cohesion 
Because a referentially creative expression seems to 
violate the selectional restrictions of its context, its use 
requires the hearer to apply a generative lexical operation 
called 'type coercion' in GL theory (see §5). The hearer 
must first apply knowledge of the lexical entry for the 
apparently inappropriate referent plus an appreciation of the 
linguistic context and the situation in order to decode the 
expression and 'coerce' the semantic type of the given 
expression to the type that the context requires, and then 
use that new type information to reconstruct the intended 
referent. 
This effort by the hearer is surely not without some 
cost, which prompts us to ask the question of why a 
speaker should make the listener go to the extra work that 
the 'decoding' of type coercion implies. Any cost that the 
speaker imposes on the hearer must presumably be offset 
by some corresponding benefit or else people would stop 
doing it. 
While we do not yet have an understanding of what 
this benefit might be, we can at this point narrow its 
character by identifying it with another set of phenomena, 
which, while also having no real explanation as yet in 
terms of their utility (but see Granville 1990 or Valduvf 
1992), seem to us to be phenomena of the same kind. 
These are the textual resources of the language known as 
'cohesion', as that term is used by Halliday and Hasan 
(1976). 
Cohesion, to Halliday and Hasan, is the defining 
property of a text qua text--what it is that makes a text a 
semantic unit rather than a jumble of unconnected phrases. 
Sophistication in the use of cohesive linguistic devices is 
what distinguishes a fluent computer speaker from an 
awkward one, e.g. the ability to correctly use pronouns, 
ellipsis, substitutions of generals for specifics, elision of 
information because it is redundant in content, etc. All of 
these linguistic resources are typified by an omission or 
substitution that a listener can only resolve by consulting 
earlier parts of the text. What we are proposing here as the 
benefit of referential creativity is that it involves an 
omission that is only resolved by consulting the situation 
in which the utterance occurred, hence our name for the 
phenomenon: "situational cohesion". 
Selecting a unit of content that is referentially 
creative--one that cannot be interpreted in its textual 
context directly but requires the listener to make a 
connection from it to some larger event or relationship that 
she knows to be salient in both her own and the speaker's 
model of the situation---creates a tie from the text to the 
unspoken but mutually appreciated situation in which the 
utterance is taking place. In just the same way that a 
normal cohesive device creates a link to an earlier part of 
the text and thereby reinforces the fact that the two points 
are part of the same semantic unit and not disconnected 
ideas, we can see referential creativity--a device that creates 
situational cohesion--as knitting the act of making the 
utterance that much closer to the situation in which it 
occurs and thereby reinforcing the link between the 
interlocutors by explicitly tieing them to the same situation 
as a precondition for the speaker being understood. 
The phenomenon of situational cohesion is one more 
piece of evidence of the central place of the situation in the 
speaker's processes, and with that the need on the part of 
the generation research community to pay increased 
attention to it and how it may be formally characterized. 3 
As a possible step in that direction, we will lay out our, so- 
far only partially implemented, conception of how 
generation is {situated} in the speaker's situation, and from 
that move on to describing elements of our generative 
lexicon and its use in a rational reconstuction of an attested 
referentially creative utterance. 
Which is by no means to say that the situation has been 
ignored in past work, as the efforts in functional theories 
of linguistics and some lines of work in philosophy of 
language will attest; see, e.g., Halliday 1978, Bateman 
1985; or Barwise & Perry 1983, Devlin 1991., but only 
that it needs a strong computational treatment that we 
have yet to see evidence of. 
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4. The processing framework 
All actions by a human agent take place in the context 
of the agent's mental model of the situation. We assume by 
hypothesis that this model is highly structured, 
compositional, and organized according to a vast number of 
reified 'situation types' (Barwise & Perry 1983, Halliday 
1978 pg. 29) that provide the prototypical assumptions and 
categorizations by which a person makes sense of the 
situation she perceives. 
In McDonald, Meteer & Pustejovsky 1987, we 
proposed a general model of the generation process as a 
sequence of incremental mappings to successive, 
progressively more linguistic and more concrete 
representations of the utterance. These begin with the 
identification by the speaker of what we call "the Relevant 
Portion of the Situation", or "RPS". 4 This is a subset of 
the total situation, that picks out just those elements to 
which the speaker is attending given her intentions as she 
commences to speak. 
Much of the organization of the RPS--the roles and 
relative salience assigned to the entities in the external 
context and to the speaker's mental entities--derives from 
the situation-type(s) governing the speaker's actions. It is 
the situation ty.pe, as an orchestrator of the speaker's 
intentions and attitudes, that we see as ultimately in control 
of the generation process. The situation type may be very 
simple, as when answering the phone or saying hello to a 
colleague, or very complex, as when being interviewed for a 
job or going out on a third date. 
We see the RPS as comprised of a structured heap of 
independent units of information of various sizes whose 
epistemological character follows the lines common to 
today's KR systems. The amount of information in a unit, 
particularly for the minimal units from which complex 
ones are composed, is a matter of conjecture. The way we 
approach this question is to work backwards from the 
phrasings and variations that we observe in language and to 
design hypothetical units with enough articulation to 
produce those texts while trying to work out an aesthetic by 
which to evaluate alternative design decisions. 
We further hypothesize that the RPS, being language 
oriented, is restricted in what it can contain. 5 Specifically, a 
The idea of giving special status to a 'relevant' portion 
of the situation, often under the construal of a particular 
situation type, is also present in the work of Halliday 
and no doubt others. We see our contribution as trying 
to give it computational consequences by tieing it to a 
means of ensuring expressibility. 
There are plainly things one can percive, categorize, and 
think about that one cannot talk about in language. 
Imagine trying to communicate what a headache really 
feels like or a sunset really looks like. One can get 
another person to think along similar lines or can, with 
some deliberate effort, work out a nearly private 
mental unit is only allowed in the RPS if it is expressible 
in the sense of Meteer 1992. We identify this property with 
whether or not the unit has a lexical entry. The lexical entry 
dictates the possiblities for the unit's realization, and 
governs its mappings. 
We view the generation process as fundamentally one 
of traversing of the units in the RPS under the control of a 
linguistic schema associated with the situation type. The 
network of interconnections among the units defines the 
paths available to the generator and the basis of judgments 
about the content that should be used. As a unit is reached 
and selected it is mapped to the first linguistic level of 
representation, Text Structure (Meteer 1990, 1992). 
The mapping to Text Structure involves three 
simultaneous and inter-constrained actions: the choice of the 
specific unit (possibly a sub-unit of the unit reached by the 
traversal), the choice or delimitation of its linguistic 
realization, and the choice of the position where it is to 
appear in the Text Structure. This simultaneous constraint 
plays an important role in our framework as we will see in 
§8, as it is the locus of the operations that lead to 
referential creativity. 
Text Structure is the level where the selected content 
is first rendered into an abstract linguistic form that dictates 
its approximate sequential order and hierarchical structure. 
Working off the Text Structure, later processes 
incrementally construct a linguistic specification that is 
• then mapped to the surface structure level of representation 
where the grammatical form of the utterance is established. 
The surface structure in turn is incrementally mapped to a 
stream of words for presentation as written text. These later 
procedures have been thoroughly described in earlier papers 
(Meteer 1992, Meteer et al. 1987). 
5. The Generative Lexicon 
Our account of referential creativity builds on 
observations made within the framework of Generative 
Lexicon theory ("GL"). This framework defines a method of 
lexical decomposition where the semantic information in 
the lexical representation is highly structured. The meaning 
of a lexical item is taken as a relation (or a set of relations) 
between all its components, with the important 
consequence that the lexical entry will include all the 
parameters that give rise to what appear to be distin& (but 
related) senses of the same lexical item when projected to 
surface structure: 
(8) a. John tripped and broke the bottle. (container of 
liquid) 
b. Let's drink this bottle, it should be good. (liquid in 
container) 
Besides the advantage of reducing the size of the 
lexicon, a generative theory of lexical semantics captures 
the underlying relatedness among different surface 
sublanguage to provide lexicalizations for perceptions, 
as when at a wine tasting, but there are always limits. 
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realizations by means of generative mechanisms operating 
over the lexical structures. One such mechanism is type 
coercion which we take to be crucial to model our notion 
of referential creativity. Informally, type coercion is a 
mechanism that allows the expression of a lexical item of a 
different type than the one expected in a particular context, 
only if that lexical item has available in its representation 
a denotation of the expected type: 
(9) a. Bob enjoys reading detective novels. 
b. Bob enjoys detective novels. 
The generalization provided in Pustejovsky (1991) is 
that those predicates that like "enjoy" have multiple 
subcategorization frames on the surface select for only one 
deep semantic type, thus in (9a) the 'deep' type selected by 
the verb is an event, as is that in (9b) where the 
complement does not directly denote an event. 
The theory of type coercion, without making any 
committment to what actual event will result from the 
coercion, states that the object in complement position has 
to have an event denotation in its lexical representation in 
order for the sentence to be acceptable. Thus the default 
interpretation of (9b) is that of 'reading detective novels'.6 
This view reduces the semantic load of the predicate 
by distributing _it across the surrounding lexical items 
whose type specifications reduce the set of possible 
interpretationsma phenomenon known in GL theory as co- 
composition. 
The decomposition of the lexical meaning is given in 
terms of the qualia structure which organizes the distinct 
facets of the meaning of a lexical item based on the four 
Aristotelian 'modes of explanation': the AGENTIVE role 
picks out that which event brings about the lexical item; 
the CONSTITUTIVE role defines the relation between it and 
its parts; the FORMAL role distinguishes it in some larger 
domain; and the TELIC role gives its purpose and function. 
These relationships not only account for regularities 
in a word's behavior, but they reflect the way in which we 
sort out what we know about the meaning of a word, such 
that the way we will use it in context will make direct 
reference to the distinct but tightly related aspects of such 
knowledge. 
A system that, like GL, captures the expressiveness of 
language without resorting to multiple listings of the same 
lexical entry has the capacity to account for phenomena 
that, like referential creativity, can be best treated 
generatively. In particular, while keeping the number of 
senses fairly constant, generative mechanisms over highly 
organized lexical structures allow for an unbounded space of 
possible interpretations which reflect the unbounded set of 
situation types and their compositional properties. 
6 This is what is taken to be the default reading. Consider 
instead the same sentence where Bob is a writer of 
detective novels, where the interpretation "writing" 
because of the sortal specification of the subject in 
determining the type of the object. 
6. A Rational Reconstruction 
Consider example 10 below, which was spoken by 
one of the authors while shoveling the snow off his 
sidewalk. 
(11) "'When we get it down like that it will stay clean for 
a couple of inches." 
The motivation behind (10) was to admonish the 
speaker's snow-shoveling partner to continue to clean the 
sidewalk thoroughly. There had been a problem with ice 
forming under footprints when there was a lot of snow, and 
this utterance reflects the observation that if nearly all the 
snow was removed ("when we get it down like that "), that 
when the next snowstorm came at least two inches of snow 
would have to accumulate before the icing problem would 
arise again ("it \[the sidewalk\]will stay clean"). 7 
What is referentially creative about (10) is that is uses 
a measurement of depth--the amount of snow that would 
have to accumulate in the course of the next stormmin a 
phrasal context whose selectionai restrictions require a time 
adverbial, i.e. a measurement of time: the duration during 
which the sidewalk will remain in the state of 'staying 
clean'. 
A 'normal' realization, one where the type of the 
adverbial fits the type expected by the predicate, might be: 
(11) "... it will stay clean for two hours." 
though it would not be communicating the same 
information since the crucial datum is the depth of 
accumulated snow, not the amount of time it will take for 
that snow to fall. 
Since the accumulation is a function of the rate at 
which the snow falls and the duration of the storm, the 
measurement of snow depth does in fact implicitly denote 
an amount of time, namely the length of time in which it 
takes that amount of snow to fall, and in so doing it makes 
that time information available through a process of type 
coercion. 
As the listener hears (10) incrementally from left to 
fight, she will have set up an expectation at the point when 
she hears "stay clean for" that she is about to encounter a 
time phrase and that they should construct an interpretation 
of it as a duration, s Instead, she encounters a measurement 
phrase. She must now coerce that phrase into a duration, 
which is possible by considering the information available 
via the lexical semantics of the phrase--information in its 
This utterance is obviously muddled and obscure when it 
comes to the fit between what the speaker was trying to 
communicate and what he actually said, but this does 
not have any impact on its value as an example of 
referential creativity. Such are the complications of 
dealing with real data. 
That listeners can construct an interpretation that quickly 
is shown from the performance of 'close shadowers' in 
experiments down by Marslen-Wilson and Tylor (1980). 
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lexical entry--and an appreciation of the elements in the 
situation that holds at that time. We expect that this is 
precisely the same information, though used in a different 
manner, as the speaker employed to sanction the use the 
phrase in that position. Let us look at what these elements 
probably were. 
First the RPS. The overarching situation type is that 
of 'shoveling out after a snowstorm', something that had 
become all too common during the winter that this paper is 
being written. Within this, we have the speaker-internal 
situation of having made an observation that a certain 
benefit will acrue if some activity is continued. This gives 
us the following likely elements for the relevant portion of 
the speaker's situation: 
• the two interlocutors cure snow-shovelers, 
• the activity of shoveling snow, 
• the likely next snow storm (a few hours away), 
• the sidewalk, 
• the ongoing problem of ice forming under people's 
footprints ('stay clear'), and 
• the thoroughness with which the fellow snow- 
shoveler was cleaning the sidewalk ('get it down 
that far'), 
• the observation that, given that thoroughness, a 
surprisingly large amount of snow would have to 
accumulate before ice was likely to become a 
problem again ('about two inches'). 
Next come rhetorical issues. How are the units of 
content in an utterance to be organized--what is their order, 
linguistic roles, prosodic tune--such that the intended 
message will be communicated. One basic rule, particularly 
for a topic-initial utterance like this one, is progression 
from 'given' to 'new': The utterance must start with an 
element that is mutually known given the situation, and 
should then progress to new elements that the hearer is 
probably unaware of. That rule provides a selection criterion 
to pick out one of the schemas available for communicating 
cause and effect (here 'achievement' and 'benefit') by fixing 
the order in which the two elements must occur. 
This gives us a "When X, Y" schema, which we take 
to be an active player, setting up the ordering for how the 
RPS is to be traversed. With this process set in motion, 
units begin to be mapped to Text Structure and from there 
to surface structure (where their grammatical properties are 
manifest) and the first words of the utterance are spoken. 
We see no reason why all of the different stages of this 
pipeline wouldn't be active simultaneously, and we further 
assume that all mappings are indelible: once made they 
cannot be retracted--all operations build monotonically on 
what has gone before. 
7. Linguistic reasoning during content 
selection 
We now pick up this process at the point where nearly 
all of the second clause has been introduced into text 
structure. We are at the moment when the complement of 
its adjunct 'for' phrase is to be added, i.e. 
"... it will stay clear for .__Z' 
The eventuality denoted by this clause (the unit that is the 
clause's source) is situated at the time of the next snow 
storm. We assume that that time was the direct source of 
the "will". 
Semantically the matrix is a persistent state and the 
adjunct is describing when it will cease to hold. They both 
derived from a complex unit in the RPS, which would have 
been queued up as a whole and its parts then traversed 
incrementally. For this unit the rhetorical considerations are 
probably overshadowed by the grammatical constraints on 
the order of the subunits. However, since it is the large 
depth of the to-be-accumulated snow that is what is 
significant (indeed, it is probably what prompted the whole 
utterance), there is a strong reason to make sure that the 
unit representing the depth of snow is positioned at the end 
of the utterance where it can receive tonic stress in the 
default prosodic tune. 
The choice of '3eor" as the preposition reflects the 
particular way that the state has been conceptualized. 
Alternative conceptualization would have yielded different 
prepositions: 'state persists while state/process', 'state 
persist(s) until event'. Here it is viewed as lasting 
throughout ('~or") some interval of time. We take it that 
this conceputalization was not a generation 'choice', per se, 
but just reflected the type of the source unit within the 
RPS. It is something that the generator must accomodate to 
in what follows, not something it was free to phrase in a 
different way. 
We think that at the level of content selection the 
generation process is so incremental and the pipeline below 
it so fast (the 'planning units' so small) that the speaker 
will have committed to a formulation in terms of the 
matrix +for adjunct before reaching the next unit in its 
path, the snow. This means that the realization of this next 
unit must be accomodated to a site in Text Structure that is 
constrained to take only an interval of time. 
On its face this is not possible, and the unit would 
ipso facto be 'inexpressible' and its realization blocked. 
However given a generative lexicon, the generator has at its 
disposal the linguistic resource of type coercion, and this 
makes new options available by in effect expanding on 
what consitutes the type of a unit. 
The information carried by the 'a couple of inches of 
snow' unit goes considerably beyond what appeared at the 
surface. In words it is something like 
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7th International Generation Workshop • Kennebunkport, Maine • June 21-24, 1994 
,the depth (about two inches) to which the snow from 
the next storm will have to accumulate before ice will form 
...' 
Obviously there is no simple lexical entry for a unit 
like this. The unit is a complex, highly interrelated object 
that makes reference to several other units (the impending 
storm, the sidewalk, etc.) that are all necessary 
concomitants of each other--the one will not exist without 
the others. Consequently its lexical entry must have an 
equally elaborated type with equally interrelated elements. 
This, however, is actually common for words in a natural 
language. 
To have a handle on it, we think of this entry as the 
lexical entry for "snow", but that is only because that word 
appears so often in the realizations that pick out its various 
aspects, and because it has a more specific content then the 
other linked words such as '~fall" or "'accumulate". Consider 
these excerpts from news articles: 
(12) a. The snow further snarled the plans of travelers. 
(process) 
b. Boston has received 24.7 inches of snow this 
month. (state, result) 
Following the symbolic presentation of Pustejovsky 
and Busa 1993, the relevant part of the entry for snow is the 
following. A full lexical entry also gives the temporal and 
aspectual relationships of the events, the linguistic 
properties of the words coordinated by this entry such as 
"depth", and other qualia roles; here we just showed the 
rules that pick out units in the current RPS. 
snow(eP,eS,x,y) 
FORMAL: depth (eS,x,location) 
CONSTITUTIVE: flakes (x, y) 
AGENTIVE: snow storm (eP,y,location) 
According to this entry, snow is polymorphic. It is 
brought about (the 'agentive') by a process, eP, namely a 
snow storm at some location 'y'. It is also the state,, of an 
accumulation of some depth of snow, 'x', at y. 
As seen by the constraint mechanisms operating at 
Text Structure, the 0nly relevant aspect of a unit in the 
RPS is its expressive semantic types, something we have 
identified with the unit's lexical entry. Here the entry makes 
reference relations of three types: a 'depth' (which is how 
one conceptualizes an amount of snow on the ground before 
it starts to melt), a mass (the snowflakes), and a process 
(the storm). There is also reference to the types of the 
parameters in those relations. Of crucial interest here is of 
course the standard time parameter in the agentive, the 
duration of the storm. The Text Structure is imposing the 
contraint that the unit convey information of type duration; 
this parameter provides it. 
9. Summary 
We have made a rational reconstruction of an actually 
attested utterance that exhibited what appears to us to have 
been a completely new pattern of semantic types, making it 
an instance of what we have called referential creativity. We 
have used this reconstruction to illustrate our design for an 
incremental content selection process. This process selects 
conceptual entities or 'units of information' from a region 
of the speaker's situation that is established at the moment 
she decides to say something, what we call the Relevant 
Portion of the Situation. Simultaneous with a unit's 
selection is its assignment to a location in the text plan as 
it exists up to that point and the determination of the 
linguistic resource to which it is to be mapped. The text 
plan is Meteer's Text Structure level of representation--the 
level at which units must be shown to be expressiblemand 
consequently there is a constraint on the selection process 
that the mapping chosen must be consistent with the 
syntactico-semantic constraints of the target location. 
Since judging the consequences of a choice of 
realization could involve a great deal of linguistic reasoning 
if the vocabulary in which the choice was deliberated were 
too detailed or too dependent on facts about surface syntax, 
we base the decisions on abstract representations of the facts 
in a unit's lexical entry, the Lexical-Conceptual Paradigms 
of Generative Lexicon theory, instead of on the entries 
themselves. In addition, we draw on GL's qualia structure 
representation of a word's meaning to indicate when a 
phrase will communicate more information than it appears 
to do looking just at its surface content. This permits the 
selection of units that would otherwise be inconsistent with 
the Text Structure location to which they are assigned, 
resulting in the need for the listener to do what GL calls 
'type coercion' to recover the meaning that the phrase is 
intended to indicate. We noted that in cases like this, the 
omission of explicit information creates a cohesive link to 
the situation in which the utterance occurs, thus reinforcing 
the integrity of the text as a semantic unit. 
Our work suffers from the lack of a real, implemented 
machine speaker that could be in real situations, have real 
intentions that lead to the identification of an RPS, and 
thereby provide a real check on whether the kinds of 
linkages of units that we have posited are coherent in a 
system that has more to do than just produce texts. We 
have accepted this limitation because it is the only way that 
we could look at language as it is really used by people, and 
with that be able to investigate a process whose 
complexity, we believe, is commensurate with what is 
happening in people's minds. 
Indeed, the only realistic reason to propose an 
incremental processing architecture like this one is to 
formulate hypotheses about the nature of language 
processing by people, not machines. If the goal were 
simply to have computers produce the best possible texts to 
fit the content, then we would surely use multi-pass, 
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7th International Generation Workshop • Kennebunkport, Maine • June 21-24, 1994 
revision-driven architectures such as the one developed by 
Gabriel (1981, 1988), which, after all, passed the ultimate 
test of a machine generation system by writing three 
paragraphs that were folded into the exposition in the 
journal article about the system and were completely 
undetectable as machine-text. 
As a hypothesis about people, an architecture should 
offer some explanation for phenomena that we can observe, 
and should make predictions about aspects that we had not 
thought to look for before. We have seen the first signs of 
such explanations when we looked closely at the contexts 
that led to referential creativity. For example, had the 
utterance about the amount of snow been based on a 
different phrasing for the temporal adjunct, then a normal 
realization would have been possible: 
(13) "'...it will stay clean until there are a couple inches 
of snow on it." 
Similarly, if example 1 had not involved the fixed phrase 
"before or after" then a normal realization of the whole 
event would have been available as discussed earlier. 
We expect that in part it is the difficulties that such 
phrasal choices create for the expressibility of the normal 
following content that contribute to the recourse to 
referentially creative utterances, where the difficulties no 
doubt combine ~vith the centrality and salience of the type- 
inappropriate unit to make the unit more available in the 
RPS than it might otherwise be. 
This suggests that referential creativity is an escape 
route from a context in Text Structure that would otherwise 
block any content from being selected. As a hypothesis 
about human processing, this may be testable through a 
close examination of a class of speech errors, a known to be 
fruitful source of insight into human processing (Levelt 
1989, Garrett 1980). This class is the pattern of 'block and 
restart' errors that are so common, even ubiquitous, in 
casual unpracticed speech that we accept them just part of 
the process of talking and don't even think of them as 
"errors". Here, for example, is such a block and restart 
transcribed off the radio during an interview. The person is 
speaking about the flooding in Mississippi and how people 
are dealing with it: 
(14) "Some of these emergency workers have not had a// 
have not been to bed for three days." 
If we allow ourselves to speculate about what this 
person might have said had he continued at the point of the 
"//" rather than restarting, a likely possibility is that he 
would have said that the workers had not had "a nap", or "a 
chance to sleep". This possible content is high frequency 
locution, just like the phrase "before or after", but it 
probably does not fit the facts of the situation. That is, we 
speculate that the intended completion was "have not had a 
nap in three days". 
We expect that it may be very often be the case that a 
block and restart occurs because the content unit just before 
the block, the last one said or partially said (given that the 
process overall is a pipeline and the speaker can be expected 
to appreciate a failure of expressibility at an early stage), a 
high frequency standard phrasing, creates a context in which 
the next unit to be said cannot be expressed. Then, if there 
is no high salience, situationally cohesive unit available in 
the RPS that might implicitly convey the information and 
allow the the speaker to make a referentially creative choice, 
then the speaker will have no alternative other than aborting 
their plan and starting anew. If such an account for block 
and restart errors proves fruitful it will provide empirical 
support for the design of the content selection process that 
we have described in this paper. 

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