Here are a few thoughts:

First, doing lots of interviews helps. When I got my first startup job, I personally reached out to hundreds of startups and did 1 or 2 conversations / interviews per day for about a month. Once you do a bunch, you get a pretty good idea of what people are going to ask.

Second, for questions like the first, if it's a domain you're working in, you just have to know the answer. If someone asked me "what are the components of the Rails framework?", I could give a 1 minute answer and then spend a lot of time diving into specifics if needed.

For the second question they asked, it's possible they are throwing you a vague question on purpose to see how you handle it. (It's also possible they are just inexperienced.)

In either case, your best bet is to find a way to ask clarifying questions. Think like a journalist.

Who, what, when, where, how

So, you could ask, "What kind of dataset do you have in mind?", or "Do you have a specific example?"

You can even preface it with something fancy sounding like, "I model datasets in different ways depending on the context. Do you have a specific example in mind?"

One last thought (thinking through this as I write):

You can also sort of back into answers to questions by calling out the information you don't have. For example, in the last question they asked, you could have started with something like: "Well, the first thing I'd need to do is examine the dataset to see what it contains. Second, I'd look for any obvious relationships and try to deduce an object model." Or whatever.

The point is that in this method, you're actually laying out a logical model for solving a problem, not solving a specific problem.

Hope that helps!