
The next design patterns we're going to discuss, are

summarization patterns. And, these are patterns that give you, some

quick easy high level understanding of your data. And we're

going to make a distinction here. We're going to talk about making

what's called an inverted index. And this is very similar

to the index you'd find in a back of a

book, or the indexing that Google does when it crawls

the web. And, we're also going to talk about numerical summarizations.

And, these are things like finding counts, how many of a certain record type, or

min and max. And min and max of course, can be used to calculate first

or last. Or calculate statistics like, mean

and median, and basically any other high level

numerical value that you can use to summarize

your data set. In this section of summarization

patterns, we'll also talk about some

interesting additional [INAUDIBLE] functionality, something that

can exist between [INAUDIBLE] reducers, known

as combiners. So, let's keep going.