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Substitute "Observer" pattern with "Pub-sub" (#348)

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topics/reference_guide/messaging_infrastructure.md
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@ -9,7 +9,7 @@ It is intended to answer why, when and how to use it.
## Rationale ## Rationale
So, what is messaging in the IntelliJ Platform and why do we need it? Basically, its implementation of [Observer pattern](https://en.wikipedia.org/wiki/Observer_pattern) that provides additional features like _broadcasting on hierarchy_ and special _nested events_ processing (_nested event_ here is a situation when new event is fired (directly or indirectly) from the callback of another event). So, what is messaging in the IntelliJ Platform and why do we need it? Basically, its implementation of [Publisher Subscriber Pattern](https://en.wikipedia.org/wiki/Publish%E2%80%93subscribe_pattern) that provides additional features like _broadcasting on hierarchy_ and special _nested events_ processing (_nested event_ here is a situation when new event is fired (directly or indirectly) from the callback of another event).
## Design ## Design
@ -170,11 +170,11 @@ Let's see what happens if someone sends a message to the target topic:
### Relief Listeners Management ### Relief Listeners Management
Messaging infrastructure is very light-weight, so, it's possible to reuse it at local sub-systems in order to relieve [Observers](https://en.wikipedia.org/wiki/Observer_pattern) construction. Messaging infrastructure is very light-weight, so, it's possible to reuse it at local sub-systems in order to relieve [Subscribers](https://en.wikipedia.org/wiki/Publish%E2%80%93subscribe_pattern) construction.
Let's see what is necessary to do then: Let's see what is necessary to do then:
1. Define business interface to work with; 1. Define business interface to work with;
2. Create shared message bus and topic that uses the interface above (_shared_ here means that either _subject_ or _observers_ know about them); 2. Create shared message bus and topic that uses the interface above (_shared_ here means that either _subject_ or _subscribers_ know about them);
Let's compare that with a manual implementation: Let's compare that with a manual implementation:
@ -207,4 +207,4 @@ We had the following then:
9. _subscriber2_ receives _message1_ and also modifies a document; 9. _subscriber2_ receives _message1_ and also modifies a document;
10. the call stack is unwinded and _actual change_ phase of document modification operation requested by _subscriber1_ begins; 10. the call stack is unwinded and _actual change_ phase of document modification operation requested by _subscriber1_ begins;
**The problem** is that document range used by _subscriber1_ for initial modification request is invalid if _subscriber2_ has changed document's range before it. **The problem** is that document range used by _subscriber1_ for initial modification request is invalid if _subscriber2_ has changed document's range before it.