What is the Royal Mail's PAF Address Database?

I'm struggling to understand what you would get from the Royal Mail if you bought their PAF file dataset of UK addresses.

I was expecting that PAF was some form of database which you would host yourself, and the Royal Mail provide APIs into that database.

However, after reading this, I'm presuming that all you get is a series of files containing the data. I can't find any obvious information regarding an API.

Are there any libraries available to help you handle these files, especially from Java?
Do you have to parse the file yourself and stick it in your own database, so you can do quick lookups from an application?
If all this is true, why would you ever bother buying this off the Royal Mail? Aren't all the third party providers, with their web based APIs, just far simpler to use - in terms of both programming and data maintenance?

Apologies if I've missed the obvious on this one, but I find the Royal Mail site lacking in information. I'm beginning to think that I've misunderstood their PAF file offering.

Solution

The postcode address file (PAF) is a set of data-files provided by Royal Mail that contain all address in the UK. My understanding is that it's normally updated every three months.

I'm aware of two companies that have products that supply APIs into the PAF data: QAS and Capscan. With these you're able to search addresses to find missing postcodes or vice versa. APIs include both web-based solutions and native calls.

Why you'd buy direct from Royal Mail? Because you'd want to write your own query tools rather rely on third party products or you want to do data-mining that other products can't provide.

Could you import into a SQL database? Yes, but only after you'd written your own PAF file parser.

Why use these over web-based tools? Because you're sitting behind an intranet, have limited internet access from servers, restrictive licensing from any web-based solution, etc.