General Lexical Representation for an Effect 
Predicate 
Martha Palmer 
National University off Singapore, 
Department of Information Systems and Computer Science 
Lower Kent Ridge Road 
Singapore 
mpaimer~nusdiscs, bitnet 
Abstract 
This paper argues that there is no reason to distinguish between lexical information 
and real-world information on the basis of the formalisms used; that both types of 
knowledge can be expressed in the same formalism. However, it Mso argues that 
there is information that is uniquely lexical in content, and this information consists 
of verb- independent definitions for thematic relations such as cause and effect that 
alter the representation of a verb depending on the presence or absence of certain 
verb arguments. 
1 Introduction 
When considering the question of whether or not lexical information can be separated from 
real-world knowledge, it must first be recognized that most lexical information in a natural 
language processing system is expressed in terms of properties defined in a knowledge base 
representing the domain model - i.e., the "world," whether real or otherwise. For example, 
semantic class constraints consist of properties such as animate or machine-part which 
are associated with generic entities. Semantics is often described as the link between 
syntax and the knowledge base, so by definition it must have one foot in the knowledge base 
camp. In the absence of concrete examples of lexical facts or rules that are provably more 
difficult to represent than real-world knowledge, it also seems reasonable to assume that 
the knowledge representation formalism used for the domain model could serve to model 
the associated lexical information. This is not intended to imply that it will be possible to 
fully represent all of both types of information.. Formalisms for knowledge representation 
have been acknowledged to be inadequate for representing real-world knowledge, let alone 
lexical information \[1\]. It does make it especially burdensome to prove that a formalism 
that is inadequate for real world knowledge is even more inadequate for lexical information. 
The question remains, is there lexical information which is uniquely "lexical" in that 
it can be distinguished from real-world knowledge albeit it may be expressed identically? 
This paper argues for the affirmative response. Given the approach to semantic repre- 
sentation implemented in PUNDIT and KERNEL \[2\], \[3\], \[10\] which is closely aligned 
to Jackendoff's lexical conceptual structures \[4\], \[5\], it is argued that the definitions of 
thematic relations such as cause and effect correspond to "uniquely lexical" items of 
information. 
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2 Reviewing the effect definition 
It has already been proposed, \[7\], \[9\], that the thematic relation effect can be formalized 
as a predicate which takes two arguments, an Intermediary and another predicate. This is 
briefly summarized here. Examples of three verbs from a domain of pulley word problems 
that include this definition in their lexical conceptual representations are connect, hang 
and suspend. 
2.1 Contact verbs 
We will first look at attach and then contrast it with connect. An example sentence 
from the pulley domain is A particle is attached #o/at\] the end of a string. The final 
semantic representation of this sentence needs to include a fixed, direct contact between 
the particle and the end of the string. This is accomplished by mapping the referent for 
theparticle, partlelel, onto one Patient role, and the referent for the end, endl onto the 
second Patient role in the following lexical conceptual structure: 1 
attach-: 
contact(Patient 1,Patient2)) 
The semantic representation resulting from this lexical conceptual structure becomes 
contact(particlel,endl). At first glance, connect seems to be quite similar to attach, 
but the possible inclusion of an Intermediary makes an important difference. Examples of 
connect as used in the pulley domain include: A particle is connected to the end of a string, 
A string connects two particles, A particle is connected by a string to another particle... 
In all of these phrases, the final semantic representation should include a fixed contact 
between location points on each of the two objects being connected to each other. In the 
first phrase, A particle is connected to the end of a string, the particle and the end are 
being attached directly to each other. In the second and third phrases, A string connects 
two particles and A particle is connected by a string to another particle, the two particles 
are being indirectly linked with each other by the use of an Intermediary, the string. There 
is still a fixed contact involved, in fact there are two fixed contacts, but they are between 
the particles and the ends of the strings, not between the particles themselves. This use 
of a string as a Intermediary to effect a connection between two objects is captured by 
the following general definition of connect which can produce distinct representations for 
the different usages of connect given in the examples here. 
connect -: 
effect(Intermediary), 
contact(Patientl,Patient2)) 
Instantiating this definition by the referents to the noun phrases from A string connects 
two particles results in: 
1 The use of standard thematic role names in the verb definitions is not intended to mislead the reader 
into thinking that the arguments to the predicates correspond directly to traditional thematic roles. They 
are simply arguments to predicates, and could just have easily been labelled Argl and Arg2, and have 
been labelled as such in various incarnations. However, the author finds it difficult to keep Argl and 
Arg2 straight, and has resorted to the thematic role names in the hopes of preserving some clarity around 
which argument is which. 
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effect(stringl, 
contact(particlel,particle2)) 
At this stage, the representation does not capture the contacts between the particles 
and the string. To achieve that it is necessary to apply the following linguistic definition 
of the effect thematic relation that is independent of the verb, i.e., it applies to more 
than one verb: 
effect(Intermediary), 
Relation(Argl,Arg2) -: 
Relation(Argl,Intermediary) AND 
Relation(Intermediary, Arg2) 
Matching this definition to our instantiated lexical conceptual structure from above 
replaces the general Relation predicate with contact, Intermediary with stringl, Argl 
with particlel and Arg2 with partlele2. It results in: 
effect(stringl), 
contact(particlel,particle2)) -: 
contact(particlel,stringl) 
contact(stringl,particle2) 
This demonstrates that the general definition given above, a classic definition of logical 
transitivity (not linguistic transitivity!), can capture the essence of the meaning of the 
effect thematic relation in that the Intermediary effects an indirect contact between two 
objects by being in direct contact with each of them. 
The principle difference between connect and attach is the possible inclusion Of the 
Intermediary. When the Intermediary in connect is not present, it is not assumed, and 
the desired representation is exactly the same as the representation for attach. This can 
be captured by a definition such as the one given below: 
effect(absent, 
Relation(Arg 1,Arg2) -: 
Relation(Argl,Arg2) 
Given our first example phrase, A particle is connected to the end of a string, the first 
representation produced would be: 
effect(absent, 
contact(particle 1 ,end 1)) 
The application of the absent definition strips off the effect predicate, and the re- 
sulting representation is identical to the attach representation given above, i.e., con- 
tact(particlel,endl). This allows us to produce two quite different semantic represen- 
tations for the different usages of connect in our example sentences. 2 
2This would also be consistent with the view that the different usages are actually separate lexical 
items, which should receive separate sematic representations, as in fact they do here. Then the principal 
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The verb-independence of the linguistic definition for effect is substantiated by ap- 
plying it to hang and suspend as described in the following section. 
2.2 Support verbs 
Two principal support verbs in the pulley domain are hang and suspend which are used 
quite similarly as in A particle is hung from a pulley by a string, Two particles are sus- 
pended from a pulley, a 
The lexieal conceptual structure for hang and suspend is similar to connect and is given 
below: 
hang -: 
effect(Intermediary, 
support(Patient, Source)) 
The first phrase, A particle is hung from a pulley by a string is treated almost identically 
to A particle is connected to another particle by a string. The string is the Intermediary, 
the particle is the Patient and the pulley is the Source, giving us: 
hang -: 
effect(string1, 
support(particle1, pulley1)) 
The same linguistic definition for effect is applied, this time to support predicates 
instead of contact predicates, and the next stage of the representation is as follows: 
effect(string 1, 
support(particle1, pulleyl)) -: 
support(particlel, stringl)), 
support (string 1 ,pulley 1 )) 
In other words, the support of the particle is the string and the support of the string 
is the pulley. The important point here is that the same verb- independent linguistic 
definition of the effect thematic relation as a logical transitive relation that applies to 
connect also applies to hang. In this case an Intermediary effects a support relationship 
between two objects by being supported by one of the objects and in turn supporting the 
other. 
However, there are differences in how this definition is applied to the support verbs. 
With connect, if the Intermediary was absent, it was assumed it did not exist. With 
these support verbs, if it is absent it is assumed that it does exist. This is captured by 
defining the Intermediary in the context of a support verb as an essential role whose 
role of the lexical conceptual structure given here becomes that of determining which lexical items is being 
used. 
3In the pulley domain, the basic predicate for hal.,g and suspend is actually location, and the presence 
of gravity allows the support relationship with the corresponding upwards and downwards forces to be 
inferred. This has been changed to support in order I to focus the discussion on the transitivity issues_This 
is not intended to imply that location would not be equally central to a more general definition of hang. 
201 
filler can be hypothesized \[8\]. This prevents the absent definition from applying, and the 
same definition that applied in our first example also applies in the second example. So, 
in Two particles are suspended from a pulley, the following instantiations occur, where 
strlng57 is an hypothetical string whose existence is assumed 
hang -: 
effect(string57, 
support(\[particlel, particle2\], pulleyl)) 
This is expanded similarly to the expansion above, resulting in: 
effect(string57, 
support(\[particlel, particle2\], pulleyl)) -: 
support(\[particlel, particle2\], string57)), 
support(string57,pulleyl)) 
This is intended to represent the information that the two particles are supported by 
the string, and the string is in turn supported by the pulley. 
2.3 Summary 
This section has argued that the logical transitivity definition for the effect thematic rela- 
tion represents knowledge that is uniquely lexical. It is derived from real world knowledge 
and is expressed in the same formalism that real world knowledge is expressed in, but is 
specifically concerned with the effect of the presence or absence of a particular type of 
verb argument. 
3 An extension of the effect predicate 
This section extends the previously defined notion of the effect thematic relation as 
summarized above by modifying it so that it can apply to the verb shoot as well. This 
provides further evidence for the argument that there exists a category of knowledge 
pertaining to the impact occasioned by the presence or absence of a particular thematic 
relation and that this category of knowledge is essentially lexical in nature. 
Standard flat predicate argument structure representations have had difficulty with 
shoot: 
John shot the turkey with a rifle. 
John shot the turkey with a bullet. 
John shot the turkey with a bullet from a rifle. 
John shot the turkey with his rifle (of?) a bullet. 
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because of the complexity of the event (or events) being represented. It has been 
argued that both a launch event and a contact event take place with the rifle being 
the Instrument of the launch of the bullet and the bullet being an Instrument by which 
John effects a contact with the turkey \[6\]. A general definition for this type of verb, 
which might also provide a core representation for other meanings or uses of shoot as well 
as similar verbs such as fire is suggested below. This definition makes use of an effect 
thematic relation very closely aligned to the notion of transitivity defined above, but this 
time used with a Propellant, the object being set into motion, as well as an Intermediary.. 
The central notion is once again one of logical transitivity, this time applied twice. 
shoot -: 
cause(Agent, 
effect_launch(Intermediary, Propellant, 
apply.force(Agent, Goal))) 
Given the sentence John shot the turkey with a bullet from a rifle, John is the Agent 
and the turkey is the Goal. The rifle is the Intermediary and the bullet is the Propellant. 
This would result in: 
shoot -: 
cause(John, 
effect_launch(rifle, bullet, 
apply.force(John, turkey))) 
This is intended to represent John as the Agent of an event in which he uses a rifle 
(which propels a bullet) to apply-force against a turkey. The representation of this event 
can be further expanded by the application of the following definition: 
cause(Agent, 
effect_launch(Intermediary, Propellant, 
apply.force(Agent, Goal)))-: 
apply_force(Agent,Intermediary) AND 
apply_force(Intermediary, Propellant) AND 
move(Propellant,Intermediary,Goal) AND 
apply_force(Propellant, Goal) 
apply_force(John,rifle) AND 
apply_force(rifle, bullet) AND 
move(bullet,rifle,turkey) AND 
apply_force(bullet,turkey) 
These predicates represent John's application of force to the rifle, (by pulling the 
trigger), which then applies force to the bullet. The bullet moves from the rifle to the 
turkey, and applies force to the turkey. Similarly to hang, even if the Intermediary is 
not linguistically realized, it still needs to be hypothesized, as does the Propellant. If the 
minimal sentence of John shot the turkey is used, then the specifics of the Intermediary 
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and the Propellant have to be left undefined, but it is clear that some Intermediary and 
some Propellant (perhaps a bow and arrow?) have been used. This is certainly not 
intended to be a complete representation of the event - the trigger is never mentioned 
explicitly - and may need to be modified substantially before it could be used. But it is 
intended to support the hypothesis that logical transitivity, as an inherent component of 
the meaning of the effect thematic relationship, adds a uniquely lexical component to 
verb representations. 
4 Conclusion 
This paper argues that the definitions of the effect predicates presented here, as well as 
the optionality or essentiallness of the roles , is a necessary part of the lexical semantics 
of the verb, which may rely heavily on real-world knowledge about launching Propellants, 
yet is still essentially lexical as evidenced by its being independent of the context. This 
in turn supports the claim that, while lexical information and real-world knowledge may 
share the same representation formalism, a distinction can still be maintained between 
information which is fundamentally lexical in nature, and information which is not. 
Acknowledgements I would like to thank Tara Mohanan for the insightful comments 
she made with respect to the representation of shoot and her comments on a draft of the 
paper. I would also like to thank Alain Polguere for his comments. 

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