Subject-predicate is one of the basic pairs of syntactic functions in the clause. Subject-predicate assignment means assigning these two functions to different constituents in the clause.
The subject precedes the predicate. The subject is the entity about which the predication is made, and the predicate is what is predicated about this entity. The subject answers the question of what / who , while the predicate answers the question of what about the subject , or who/what it is . For example,
(1) xiǎo lián zǒu-le. Xiao Lian leave-PEF. ‘Xiao Lian left’.