How to get free-form linguistic input to act on a previous output?

Question

It seems that Mathematica is capable of taking free-form input that acts on previous outputs (see "separate color channels"), but I'm having trouble getting it to work in my case.

I've got =countries on the caspian sea returning a useful list of countries, but when I say =flags of those countries, Mathematica seems to not understand that I'm referring back to the output of the previous step. Even if I had to say =map over those explicitly, I'd be happy to, but it doesn't seem to work.

So a few possible thoughts on what would help solve my problem:

• Are there any attempts anywhere at writing down the sorts of things that one should expect free-form input to support? I'm willing to learn how to speak its language if it'll help me help it help me.
• Does anyone have a successful example of Mapping over a list using free-form linguistic input?

Answer 1

Note

This answer assumes the most optimistic version of this question is "no, you cannot refer to the last output in words" and instead assumes you're happy using the WolframAlpha function.

Answer

In my experience = and == should not be expected to give reproducible output over a reasonable time period. It's better since V10 with the introduction of entities. If the output of a free-form input is a list of entities I'd expect something as follows to be relatively trustworthy:

Then I can use the output in the WolframAlpha function (note if I had M10.1 I would use StringRiffle):

WolframAlpha["flags of " <> Riffle[ToString /@ %, " "]]

The output is reasonable