Difference between ことになったand ことになっている？

[MizukoHito]

Uh, hi.

my textbook is teaching the ことになった and ことになっている constructions, which mean "it was decided that X does~" and "it's been decided that X does~" respectively, but i can't really see the difference between the two.

The book says that ことになった places more emphasis on the decision making. But then, in the example questions, the only difference is one word.

[SomeStupidName]

になった sort of implies a finality, whereas っている generally refers to a continuous process. I don't imagine your book is really focusing on temporal placement quite yet judging by what you've said.

Both translations are good as translations, but don't provide good explanations for learning purposes. Think of it this way- in English, hearing "it was decided" sounds like something that happened a while ago that can't be changed (court decisions, maybe?), but "it's been decided" is generally said if it's just been decided (i.e., "It's been decided, we're painting it blue. Any objections?").

Hope that clears it up, but there might be another nuance your book is going for that I've missed. If any native speakers/seasoned veterans have anything to add, do it by all means.

[Hyperworm]

the ことになった and ことになっている constructions, which mean "it was decided that X does~" and "it's been decided that X does~" respectively

"it was decided" sounds like something that happened a while ago that can't be changed (court decisions, maybe?), but "it's been decided" is generally said if it's just been decided

While that seems to be true, I disagree with the implication that
ことになった happened a while ago
ことになっている just happened

In fact I think it's the opposite. ことになった indicates the change (or decision) was just made; ことになっている indicates that we're in an ongoing state of things having been this way (for some time).

Am I disagreeing with the book here?

[MizukoHito]

Yeah, I think you two are right about ことになっている meaning an ongoing or continuous process. It kind of makes sense, since my book also says that it's used when talking about traditions and common practices, etc.
Like:
日本では、家に入る時、くつをぬぐことになっています。

[squarezebra]

If its helpful, I think of ことになっている as making something become 'customary'. As a result of it being decided in the past (ことになった）it has now become customary (ことになっている)

[MizukoHito]

Oh, I see! The does make sense. Thanks for the help, everyone