Map Reduce & EBII

Map Reduce & Event Based Implicit Invocation

Is map reduce related to any previous patterns we've read? How are they the same, how are they different?

It is similar to the Java Fork/Join Framework. A problem can be split into smaller parts that can be done in parallel to improve efficiency. At the end they are combined to form the final answer. In the java fork/join framework the worker threads could also steal jobs from other workers in order to improve the efficiency even more.

How should failures and errors be handled? Should the framework handle errors, or the application developer?

I think it should be on the application developer to handle the errors. Just like how the application developer uses the simple framework to define a map and reduce function, they should also add error handling.

Are there any interesting uses of map reduce anybody has come across?
I only first heard about Map reduce last year and have never seen it used in my day to day job.


Event-based implicit invocation

How is this pattern related to the well-documented observer pattern and publisher/subscriber patterns? Are they the same? How are they different?

This pattern is very similar to the observer pattern. They both have a list of “listeners” that will get called when a certain event happens. In this implementation, it is possible that the announcer can call a component directly when an event happens, but that component should have the ability to ignore the message. In the pure form of this pattern, the announcer does not know exactly if anyone is listening to the event.

Are there any good real world examples of this pattern, besides what the authors mention?
The new google wave probably will use a pattern similar to this. Google wave is "a personal communication and collaboration tool” that will merge email, IM, wiki, and social networks together. I am currently waiting to try out the beta. (Crosses Fingers)