As well, the uniform treatment of complements and adjuncts in terms of thematic relations does not absolve the computational linguist from the task of identifying the subcategorized constituents of verb phrases (and similarly, NPs and APs), so as to guide syntactic and semantic expectations in parsing and interpretation. And these subcategorized constituents correspond closely to the complements of the verb, as distinct from any adjuncts. Nevertheless, thematic role representations are widely used, in part because they mesh well with frame-based knowledge representations for domain knowledge. These are representations that characterize a concept in terms of its type (relating this to supertypes and subtypes in an inheritance hierarchy), and a set of slots (also called attributes or roles) and corresponding values, with type constraints on values. For example, in a purchasing domain, we might have a purchase predicate, perhaps with supertype acquire, subtypes like purchase-in-installments, purchase-on-credit, or purchase-with-cash, and attributes with typed values such as (buyer (a person-or-group)), (seller (a person-or-group)),  (item (a thing-or-service)), (price (a monetary-amount)), and perhaps time, place, and other attributes. Thematic roles associated with relevant senses of verbs and nouns such as buy, sell, purchase, acquire, acquisition, take-over, pick up, invest in, splurge on, etc., can easily be mapped to standard slots like those above. This  leads into the issue of canonicalization, which we briefly discuss below under a separate heading.