Simple extensional sentences take the form
Node:Path = Extwhere Node is a node, Path is a simple path, and Ext is a simple value. Extensional sentences derivable from the examples given in Section 2 include:
Do:<mor past participle> = done. Mow:<mor past tense sing one> = mow ed. Love:<mor present tense sing three> = love s.Simple definitional sentences take the form
Node:Path == Def.where Node and Path are as above and Def is an arbitrary descriptor sequence. Definitional sentences already seen in Section 2 include:
Do:<mor past> == did. VERB:<mor form> == "<mor "<syn form>">". EN_VERB:<mor past participle> == "<mor root>" en.Each of these sentences corresponds directly to a DATR statement. However we extend the notion of a sentence to include an abbreviatory convention for sets of statements relating to a single node. The following single sentence:
Node: Path1 == Def1 Path2 == Def2 ... PathN == DefN.abbreviates (and is entirely equivalent to):
Node:Path1 == Def1. Node:Path2 == Def2. ... Node:PathN == DefN.Extensional statements may be similarly abbreviated, and the examples used throughout this document make extensive use of this convention. Such compound sentences correspond to a number of individual (and entirely independent) DATR statements. In this connection, it is worth reiterating that DATR descriptions correspond to sets of statements: the order of sentences, or of definitions within a compound sentence is immaterial to the relationships described.
Finally, there is a pragmatic distinction between definitional and extensional sentences akin to that drawn between the language used to define a database and that used to query it. DATR interpreters conventionally treat all extensional sentences as ``goal'' statements, and evaluate them as soon as they are encountered. Thus, it is not usually possible, in practice, to combine definitional and extensional sentences within a theory. It is not obvious that one would ever wish to do this anyway, but the possibility is explicitly left open in the original definitions of E&G 1989a. Such a statement would respect global inheritance but not local inheritance and could conceivably be useful to achieve some exotic effect.