Hardware Reference
In-Depth Information
Physical Identification
The process of identifying physical objects is such a fundamental part of our experience
that we seldom think about how we do it. We use our senses, of course: we look at, feel,
pick up, shake and listen to, smell, and taste objects until we have a reference—then we
give them a label. The whole process relies on some pretty sophisticated work by our
brains and bodies, and anyone who's ever dabbled in computer vision or artificial intel-
ligence in general can tell you that teaching a computer to recognize physical objects is
no small feat. Just as it's easier to determine location by having a human narrow it down
for you, it's easier to distinguish objects computationally if you can limit the field—and if
you can label the important objects.
Just as we identify things using information from our
senses, so do computers. They can identify physical
objects only by using information from their sensors.
Two of the best-known digital identification techniques
are
optical recognition
and
radio frequency identification
(
RFID
). Optical recognition can take many forms, from
video color tracking and shape recognition to the ubiq-
uitous barcode. Once an object has been recognized by
a computer, the computer can give it an address on the
network.
Like locations, identities become more uniquely descrip-
tive as the context they describe becomes larger. For
example, knowing that my name is Tom doesn't give you
much to go on. Knowing my last name narrows it down
some more, but how effective that is depends on where
you're looking. In the United States, there are dozens of
Tom Igoes. In New York, there are at least three. When you
need a unique identifier, you might choose a universal
label, like using my Social Security number, or you might
choose a provisional label, like calling me “Frank's son,
Tom.” Which you choose depends on your needs in a
given situation. Likewise, you may choose to identify
physical objects on a network using universal identifiers,
or you might choose to use provisional labels in a given
temporary situation.
The network identity of a physical object can be centrally
assigned and universally available, or it can be provisional.
It can be used only by a small subset of devices on a
larger network or used only for a short time. RFID is an
interesting case in point. The RFID tag pasted on the side
of a topic may seem like a universal marker, but what it
means depends on who reads it. The owner of a store may
assign that tag's number a place in his inventory, but to
the consumer who buys it, it means nothing unless she
has a tool to read it and a database in which to categorize
it. She has no way of knowing what the number meant to
the store owner unless she has access to his database.
Perhaps he linked that ID tag number to the topic's title, or
to the date on which it arrived in the store. Once it leaves
the store, he may delete it from his database, so it loses
all meaning to him. The consumer, on the other hand, may
link it to entirely different data in her own database, or she
may choose to ignore it, relying on other means to identify
it. In other words, there is no central database linking
RFID tags and the things to which they're attached or the
people who possessed them.
The capabilities assigned to an identifier can be fluid as
well. Considering the RFID example again: in the store,
a given tag's number might be enough to set off alarms
at the entrance gates, or to cause a cash register to add
a price to your total purchase. In another store, that
same tag might be assigned no capabilities at all, even
if it's using the same protocol as other tags in the store.
Confusion can set in when different contexts use similar
identifiers. Have you ever left a store with a purchase
and tripped the alarm, only to be waved on by the clerk
who forgot to deactivate the tag on your purchase? Try
walking into a Barnes & Noble bookstore with jeans you
just bought at a Gap store. You're likely to trip the alarms
because the two companies use the same RFID tags, but
they don't always set their security systems to filter out
tags that are not in their inventory.
