[OSM-talk] Postcode searches in Namefinder

[David Earl]

I've implemented some changes to the experimental UK postcode searches
in the Namefinder.

And for everyone I also made it ignore leading and trailing numbers in 
the first search term, so searching for "31 Hinton Road, Fulbourn" or 
"Via Giordano 14, Milano" will still get a hit even though you quoted 
the number (which is ignored - in the longer term, I propose to process 
these with respect to the Karlsruhe schema for house numbers)

It's not the full address parsing I mentioned recently, but it is one 
small step in making things a bit more flexible.

Postcode changes:

1. you can now search for UK postcode prefixes, e.g. CB21. These are 
just OSM nodes.

2. You can qualify your search with a postcode or postcode prefix or a
place name in combination with this, e.g.
   The Bakers Arms, CB21
   The Bakers Arms, Fulbourn CB21
   The Bakers Arms, Fulbourn, CB21
   The Bakers Arms, CB21 5DZ
   The Bakers Arms, Fulbourn CB21 5DZ
   The Bakers Arms, Fulbourn, CB21 5DZ
In the latter three cases the last part of the postcode is ignored. For 
historical cultural reasons, this is more likely to be used naturally by 
Londoners, as in "Cadogan Square, London SW1" or just "Cadogan Square, 
SW1" (You still need the comma for the time being). A postcode (prefix) 
on its own acts as if it were a place name, and with a place name acts 
as if it were in the is_in, and the place has to be within 60km of the 
postcode - the largest postcode area in Caithness is about that big (you 
did know that if you put a third term it looks in the is_in - as in "The 
Bakers Arms, Fulbourn, UK"? Commas required there).

3. Full postcode searches (i.e. searching just for "CB21 5DZ") won't
produce wild results any more hopefully. It's still possible the 
postcode may not get a comprehensible address to search for, but once it 
does it shouldn't give you a result elsewhere in the world. (Previously 
it might have determined that the postcode was Foo Street, Barton, but 
then located a Barton somewhere else in the world which also happened to 
have a Foo Street within searching distance of it and return that 
instead. Because it now qualifies the search with the postocde prefix as 
above, it has to find the closest instance of the street to that 
postcode area centroid).

4. You only get one result back for a full postcode search. Previously 
you could get extraneous alternatives elsewhere also listed.

Problems to trac as usual please.

David