Figure 2.6: Sort hierarchy of content objects
Figure 2.7: Sort hierarchy of qfpsoa objects
Following standard HPSG, I assume that the content value of a verbal lexical entry is of type psoa and that a psoa is defined for a nucleus feature of type qfpsoa, as summarised in Figure 2.6. I depart from the standard definition of qfpsoa, however, instead assuming a hierarchy as indicated in Figure 2.7. The sort qfpsoa is divided into four main subsorts: sit-desc (situation description) which will be used to reflect the semantic representation of a situation, relation-objs which is the type of all basic semantic relations including those for both nouns (thing) and verbs (situation), thematic which will capture thematic elements of either internal or external semantics, and op-soa which will capture the semantics of different kinds of operator adverbials, such as frequentatives (freq-op) and duratives (dur-op).
The type sit-desc is defined for attributes internal, with
value of type situation, and external, with value of type
ext-desc. I assume a lexical constraint on the
feature structure associated with a verb which requires the
synsem:content:nucleus field of a verb to be of type
sit-desc. In this structure the
internal semantics of a situation is held distinct from its external
semantics. This must be represented in the lexical entry for verbs,
and not just at the sentence level, due to the mechanisms of
the Semantics Principle of HPSG. This principle is shown in d93
(Pollard and Sag 1994:322).
In a headed phrase,
(Case 1 - e.g. for a constituent headed by a verb)
if the semantic head's content value is of sort
psoa, then its nucleus is token-identical to the
nucleus of the mother;
(Case 2 - e.g. for a constituent headed by a noun or preposition)
otherwise, the content of the semantic head is token-identical
to the content of the mother.
Through this principle, the semantics of a sentence is projected from the semantics of the main verb of the sentence, since a sentence is a constituent headed by a verb. This means that if the internal/external situation semantics distinction is made within the content:nucleus field of a verb at the lexical level, it will be passed up to the sentence level via the Semantics Principle. As a verb combines with its arguments, their contents will be incorporated into the internal semantics characterising the situation expressed in the sentence. Adjuncts will be treated in such a way as to account for the possibility of their incorporation into either the internal semantics or the external semantics of the situation (see Chapter 3).
Figure 2.8: Sort hierarchy for Semantic Objects
Figure 2.9: Sort hierarchy for thematic relations
The type qfpsoa is rooted at sem-objs, along with other semantic types, as indicated in Figure 2.8. Included in this (sub-)hierarchy is the definition of the type ext-desc. This type is defined for an attribute, thematic, which will capture thematic elements of a situation. The hierarchy of thematic objects is partially specified in Figure 2.9. The attributes for which a thematic object can be defined correspond to Jackendoff's subordinating relations, and reflect different kinds of situational information which can be added to the description of a situation via clausal modifiers.
The use of an inheritance network for characterising this thematic information is inspired by the subsumption hierarchy defined in Wechsler wechsler:91 for sorting psoas according to valency, and has two basic motivations: (a) it allows for explicit specification of restrictions on combinations of thematic PPs via missing links in the thematic type hierarchy (a theoretical possibility, although I haven't explicitly investigated it) and (b) the type of a thematic attribute will precisely reflect which thematic entities have already been added to a sentence. The latter occurs as a result of moving down the type hierarchy (to more specific subsorts) as thematic elements are added. Multiple modifying phrases of the same thematic type do not appear to be possible, and this approach allows redundancy constraints on thematic entities to be implemented. Sentences such as d94, containing two for-to phrases, would be ruled out.
* Peter sang to Mary to please her to make her happy.
I will assume, although it does not appear in the partial thematic hierarchy represented in Figure 2.9, that each type will also have a ``grounded'' subtype which cannot be extended. For example, the type for-to will have a subtype for-to_only which itself does not have any subtypes. It will inherit only the attributes of its supertype, in this case only the attribute for-to. Similarly, the type for-to_effect will have a grounded subtype for-to_effect_only defined for attributes for-to and effect but with no subtypes. These grounded subtypes will be used in the verbal relation hierarchy to constrain the thematic elements which can be associated with particular relations (see Section 3.3.3).
The type thematic has an attribute them-arg (thematic argument) which will reflect which index from the internal or external semantics plays a role in the thematic situations. This will be used in Chapter 3 in accommodating prepositions which can modify either the internal or the external semantics.
The type ext-desc is also defined for two additional attributes: sit-ind and restr. The former attribute captures the situation index which is associated with the situation expressed by the sentence as a whole. This will be anchored to the main eventuality expressed by the verbal relation, through the constraint on the type sit-desc specified in d97.
The restr is a restriction feature, analogous to the restriction feature for nominal objects (type nom-obj), which will reflect any semantic restrictions on the situation. These will largely come from restrictive adjuncts such as temporal and locative adjuncts and will restrict some aspect of the sit-ind.
The sem-objs hierarchy also contains the declaration of the
index type. This type is divided into two subsorts. The
first, nom-ind, reflects the standard HPSG nominal index
declaration. The second, sit-ind is the type of the indices
which will be associated with situations. Building on ideas in
Kasper kasper:93, which treats some situations as located
in space and time and others as unlocated, sit-ind is divided
into two subtypes: loc-sit, defined for attributes
location and time, and
unloc-desc, not defined for either attribute.
Figure 2.10: Sorts associated with paths
Figure 2.11: Sorts associated with places
The types path and place correspond directly to the ontological categories path and place proposed by Jackendoff (1983, 1990). They are integrated into a typed inheritance framework as shown in Figures 2.10 and 2.11. Different kinds of paths (subsorts of type path) are defined for features indicating which part of the path is in focus: the source (source-path), the endpoint (endpt-path), or a location at some other point along the path (via-path). Each feature takes an object of type place as an argument. The place hierarchy is divided into subsorts corresponding to different areas relative to a location of thing which are relevant: the place of interest could be at the location, on the location, etc. This hierarchy clearly does not exhaust the possible relations that can hold between a location and a located entity, but simply serves as an approximation for the purposes of this thesis. For a fuller investigation of spatial prepositions, see e.g. sablay:95.
Figure 2.12: Prepositions defined in the sort hierarchy
A hierarchy of preposition types, rooted at prep is shown in Figure 2.12. The motivation for these types will be outlined in full detail in Chapter 3, but it stems from the observations made in Section 2.5.1 that modifiers (including modifying prepositional phrases) can be either external or internal. Prepositions which can be used for external modification will be of type adjunct. Prepositions which can be used for internal modification will be of type pseudo-complement (this terminology will be explained in Chapter 3). Operator adverbials (e.g. frequentatives, duratives) will be headed by prepositions of type operator and will be constrained to have a content:nucleus value of type op-soa.
Figure 2.13: Proposed situation and rel sort hierarchy
In Section 2.4.3 I outlined extensions to Davis' (1995) relation hierarchy which are necessary for achieving the goals of this thesis. A portion of the resulting hierarchy can be found in Figure 2.13. I have maintained the top-level relation sort assumed by Davis, rel, for compatibility with his linking theory and because not all relation sorts correspond directly to a particular kind of situation (either a state or event). I have, however, added another top-level relation, situation which has subsorts state and event. The hierarchy rooted at situation cross-cuts the rel hierarchy, essentially categorising particular relations in the rel hierarchy as either states or events. This categorisation was motivated in Section 2.4.2.
The hierarchy also reflects the introduction of various sorts discussed above, derived from Jackendoff (1983, 1990): conf-rel, extend-rel, orient-rel, go-rel (and its subsort ch-poss-rel) and typeact-inch-rel. It also shows the addition of creation-rel as distinct from ch-of-st-rel, given the differing presuppositions of a change-of-state verb as compared with a creation verb, mentioned above in the discussion of complementary polysemy.
In proposing this sort hierarchy, I adopt the basic architecture as assumed by Davis, with the changes to the relation argument type discussed in Section 2.4.3 (A situation index). The features which are defined for the various sorts rooted at rel in Davis' hierarchy will also be defined for those sorts here. I assume that act-rel is defined for a feature act of type index, und-rel for a feature und of type index, and so on. The thematic elements (acc-ev, effect, means, etc.) are treated differently than in Davis' framework in that they are bundled together under a single attribute thematic which can be associated with an event but not a state. The value of this feature is of type thematic, as described previously, shown in Figure 2.9. Internal verb semantics can thus incorporate the same kind of thematic relations as external verb semantics.
This sort hierarchy would be elaborated to represent further verbal relations, including relations such as notion-rel and influence-rel as depicted in Figure 2.2 but not explicitly shown here. Each additional relation would inherit from (at least one of) the subsorts represented in Figure 2.13 and would have specific entailments associated with its arguments. In the remainder of this thesis I will introduce as necessary subsorts of situation and rel to reflect the semantics of particular verbs, and I will assume that they are inserted into the hierarchy in the appropriate place.
