I hate how we format dialogue. I believe convention has gotten too heavy and we need to think a little more about logic. That being said, my question, to be more specific, is asking about labels for sentences with dialogue.
Let's use this sentence for an example: Bob said, "I like steak."
Now, I have seen grammars look at the structure in a few different ways. For one, you could look at it as if the speech is a direct object following the reporting clause. However, the problem with that is that this would be the only case where the subject and verb are separated from the object with a comma.
Another way that you could look at it is in comparison to a comment clause. However, if you do that, then the reporting clause, "Bob said", would technically not be obligatory, and at times, this may be true, as we see dialogue existing all by itself. However, there are times when the reporting clause is obligatory to its fullest regard; "I like steak", Bob said, and then he picked up piece of meat.
So, what is it? What is the relationship between the speech and the reporting clause? Or, is structures featuring dialogue simply so engulfed within their own gradient that we simply have to recognize it as something independent?