> > why try and encode all that information in the first place?
> > its rf ID not rf encyclopedia.
> > 1024bits worth of ID should probably cover every possible 
> product that 
> > could be sold You then have a database with the product 
> ID's against 
> > the items. Fruit+veg etc go into the bag, the sales person 
> says this 
> > bag has carrots in it. The computer takes the weight of 
> carrots, and 
> > the fact that it is carrots and sticks that item in the database.
> > When you get to the checkout your cart is read, That ID is 
> pulled out 
> > and the fact you have 12.2354435kg of carrots is added to 
> your total.
> > You aren't going to make something programmable cheap 
> enough to work.
> > I'd wager a coke that any time somebody says they are 
> "programming" a 
> > rfid tag when they wave it near the same device that reads the tag, 
> > that that is what is actually happening. They are just reading the 
> > tags value and telling the computer to associate this ID 
> number with entity X.
> 
> The someone has to associate the tag to 12.235kg of carrots, 
> it just happens in advance, so no labor is saved for the store. 


The problem has already been long solved with bar codes, and will be solved
with RFID.

If I go to my local supermarket and buy a 2kg bag of potatoes (if it's good
enough for Dan, it's good enough for me), it will have the bar code
9300633098841 on it.  This code has been assigned to the grower/packer, and
everyones database has it recorded as a 2kg bag of spuds.  That's
pre-packaged.  I pick it up, it gets waved over the scanner, and the price
pulled from the server.

If I buy them loose, that's a different story.  That's called 'variable
measure'.  They can be weighed there, and a bar code added.  The range
starting with 22 (and a couple of others) has been set aside for this.  The
format is something like 22IIIIPPPPPPC, where I is the item, P is the price
and C is the check digit.  So if carrots are $2/kg, my 12.235kg of carrots
gets a label with the barcode 22987600024471 on it.  The backend system sees
9876 as the item, and 2447 as the price ($24.47).  Quantity is calculated.
RFID will be similar.

The bar code on books (non-US) is essential the ISBN number.  While on
books, they have a pricing bar code on them too.  After the main bar code,
there's shorter one, that's the price.  (I know it's almost useless, ok?)

You can get field programmable RFID tags, but in most cases it's as you say,
you're just getting the system to recognise the tag which has a unique
serial number.  Still, where's my Coke?  A cheap programmer is easy.  The ID
is set thru thin wires acting as fuses.  Burn out the ones you don't need.
Cheap, simple, fast.

They're a bit expensive to put on a bag of spuds at the moment though.

Roll on 1 cent programmable tags!

Tony

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