Is it okay if research problem is vague in the initial phase of research? In short, I am a Ph.D. student computer science ( theory ) currently in the mid-stage. I have one serious doubt about the research process. I have worked on just two problems in the past and from that experience, I have felt that the research problem in the initial phase of research will be vague ( means research problem will be broader and somewhat less clear ) and as we start working on the problem, it will become clear and many times we will change the even original research problem. In the end, we will think about what results, we have and on the basis of those results, we will again change the research problem ( if needed ). There are a few problems with the above research process


Takes More time
More frustrations etc


Is the research process will be the same even after my PhD, I mean or I will become more careful with time which may lead to giving me a better way to do research.

Question : Is it okay if research problem is vague in the initial phase of research?
In my opinion this is the definition of "research" everything else is "development". Of course, from "devlopment", serious research questions may be derived. 

In my personal opinion, a PhD work whose proposed result is known from the beginning is worthless.

It's a different story if the problem is too large for one person or maybe not solvable at all - then it needs to be re-adjusted based on the experience made so far. But this process can / shall be part of the PhD!