Xui wrote:I have quoted enough sources to prove my point, while you cannot prove yours. I have nothing to say anymore.
The sources you quote are mainly from pedagogical grammars. Pedagogical grammars are intentionally simplified so that students - and often, teachers - can have an easier life.
Here is a more expanded - though not complete- view of the perfect aspect:
The English perfect has as many as five readings, illustrated by the most salient interpretations of the sentences in [1a-e].
[1] a. Existential: Fred has visited Paris several times.
b. Universal: I have known him since 1960.
c. Resultative: The police have probably caught the suspect by now.
d. Recent Past: Archduke Ferdinand has been assassinated in Sarajevo.
[\hot news" June 28, 1914]
e. [Stative Present: I've got (=I have) something to tell you.]
---------------
Stan has visited here since 1998.
Two meanings possible:
He has been here one or more times in the intervening time between 1998 and now.
He has regularly visited here in the intervening time between 1998 and now.
---
Stan has worked here since 1998.
Three meanings possible:
He has worked here one or more times in the intervening time between 1998 and now.
He has regularly worked here in the intervening time between 1998 and now.
He still works here.