(1) Subject-predicate-object = subject+notional verb+object. Be is a relative verb and cannot be used as subject, predicate and object.
For example, I love you, I is the subject, love is the predicate verb, and you is the object.
(2) main system table = subject+verb (the most common is be, and there are also verbs such as "five senses" feeling, eyes, sound, smell and taste, such as become, grow? )+predicative (nouns, pronouns, adjectives, adverbs of time and place, prepositional phrases, predicative clauses? Wait).
If I am a boy, this sentence has no object and belongs to the main system table. I is the subject, the connecting verb am is the predicate verb, and A boy is the predicate. Connecting verbs and predicates are combined into predicates, indicating that in the main system table, predicates ≠ predicate verbs.
In a word, copula and object cannot exist at the same time. The copula is followed by the predicate, and the object is followed by the predicate.
Extended data:
subject
The subject is the center of the sentence, indicating who or what is said, and its position is generally placed at the beginning of the sentence, and the subject is generally not omitted in English. The subject is mainly composed of nouns, pronouns, gerunds, infinitive verbs or infinitive phrases. Clause, some fixed phrases acts as. Conjunctive verbs include be verbs and modal verbs. The predicate follows the copulative verb and mainly expresses the state of the subject and other properties.
For example:
1. Li Lei is a boy from China. (Li Lei is both a noun and a subject. )
Li Lei is a boy from China.
He comes from England. He is a pronoun and a subject. )
He comes from England.
Feeding birds is my hobby. ("Feed the birds" is a gerund phrase as the subject. )
Feeding birds is my hobby.
4. She is right. ("What she said" is a clause as the subject. )
Translation: She is right.
Baidu Encyclopedia-Main Family Table Structure
Baidu Encyclopedia-Subject Predicate Object