Student or Learner
Having spent some two and a half years in China over several visits, I don't remember ever going through a phase we in the United States refer to as "culture shock." This period of difficulty in adjusting to a new culture would probably have set in during my semester at Peking University, my first extended period away from the United States. It did not.
Having grown up in the United States, I had never seen a university surrounded by high, cement walls. My idea of a university, based on having seen scores of them in different states of the US,was that it was a place of life and learning, an integral part of the community in which it was located, open not only to the students of the school itself, but fully accessible also to students from other schools and to the broader public.
I just know the function of continuation for present perfect tense. Why does it use "having seen" here?
What's wrong or different if I use " based on seeing" here?
Actually it's not really the present perfect here, it's a gerund. So, of course is "seeing" (which is today considered perfectly correct in this context.) The addition of "having" allows the speaker/writer to emphasize the fact that his/her experience of universities is not restricted to the present.