Stock purchases and stock quote data

I apologize for being rather vague here, but I'm working on a project involving stock data and stock purchases. I'm sure I'm going to end up having to get a broker in开发者_Go百科volved, but I was wondering if anyone knows of any documentation on the underlying technology involved with existing trading sites, as well as the channels through which systems like google finance get their information.

Note that I already know of the APIs from yahoo and tdameritrade that send out the data, I'm interested in the channels through which that data travels to them in the first place.

They're most likely getting the data feeds from one or more of the usual suspects (ie, Reuters, Bloomberg and the like). You've probably noticed that the feeds on the publically accessible websites are delayed by 15-20 minutes compared to the real time feeds. Keep that in mind in your application, if you need proper up to date/real time market data it'll cost you a fair penny.

Those firms trading directly on the exchanges obviously have access to the data from the actual exchange - that's what you (have to) use in real time and algorithmic trading. However, the above mentioned companies (and I'm sure there are a few more, these are just the ones that most people are familiar with) are usually the data providers for those trading via intermediaries.

For reference data on stocks (as opposed to actual stock quote data), Mergent ( http://www.mergent.com ) is one of the data suppliers and has been collecting the data for decades. It has a set of APIs at http://www.mergent.com/servius