For subject-type relative clauses, where the antecedent is acting as the subject of the clause, a B connector serves to connect the noun to the verb of the relative clause. Nouns have a B+ connector. Notice that this is optional; it is also &ed with the S+, SI-, O+, and J+ connectors, meaning that one of these connectors must be used whether or not the noun takes a relative clause. Verbs have a B- connector which is orred with their S- connectors; if a verb is in a subject-type relative clause, it may not make an S connection as well.
For subject-type relative clauses, the relative pronoun who is mandatory. For this purpose, verbs have a Z- connector anded with their B- connector. Who has a Z+ connector; therefore it can fulfill this need. However, it also has a C- connector anded with its Z+ connector; this must connect back to the C+ connector on nouns. This allows the following:
to 20bp
For object-type relative clauses, the same B+ connector on nouns is used. However, this time it connects to the other B- connector on verbs, the one which is orred with the O+ connector and which is also used for object-type wh- questions.
In this case, the relative pronoun who is optional. Notice that nouns have optional C+ and CL- connectors which are anded with their S+ connectors. These are used when the noun is the subject of an object-type relative clause. When who is not present, the C+ connector on the antecedent noun connects directly to the C- on the subject of the relative clause:
to 20bp
When who is present, the C+ on the antecedent connects to the C- on who; this forces the CL+ to connect to the CL- on the subject of the clause:
to 20bp
This system successfully rejects the following incorrect sentences:
*The dog chased cats died
*
*The dog who chase cats died
*
*The dog who John chased cats died
*
*The dog John chased cats died
*
*The dog who chased died
The following incorrect constructions are accepted, but can be weeded out in post-processing:
*The dog did John chase died
*
*The dog who John died Mary chased died