Beginning with the military in the '50's, scientists and engineers have built a connected series of data networks that provide us with pictures of cats, among other, less-important things like email, online scholarly journals, Yelp! reviews, interactive maps, etc. There are many different kinds of computer networks, the most famous being the Internet (maybe you have heard of it, I don't know). These days, data is sent from a source to an end-user through packaging the information with source and destination information. These packets of data can travel through physical and virtual topographies in order to reach their destination.
The physical structures of computer networks include different kinds of cables (twisted pair for telecommunications, coaxial cable for TVs, optical fiber for lots of cat pictures travelling under the ocean, etc); wireless technologies send data through earth-bound terrestrial microwaves (this week's Term of the Week) or up into space via satellites, the ubiquitous cell phone towers blinking in the night, and radio frequencies.
Once the cat picture has raced across a physical structure, it encounters a node, which is a kind of door into the destination. These doors have specific addresses (NIC) and codes (MAC) that allow the cat picture to locate the correct destination and obtain access; once it finds the right place, the data gets "scrubbed" by a repeater. Sending the cat picture from one network, say a WAN, to another (LAN, or HAN? Maybe? This is conceptually difficult for me, I admit) requires that these networks communicate with one another; routers and modems regulate this process, and firewalls protect it.
The digital structure of computer networks is different than the physical topology. Network designs vary in how many connections there are between participating nodes; the more connections, the better, but more connections means a higher cost. On top of this, virtual networks can be built on top of existing networks.
The links between these networks are governed by communications protocols such as the Ethernet family, which results in the inability to mooch your neighbor's wifi because it requires a "wireless access key"; Internet Protocol Suite, which the Wikipedia article calls "the foundation of all modern network", and manages to govern information exchanges over an unreliable network; SONET/SDH; and Asynchronous Transfer Mode, which is still relevant for connecting an ISP to someone in their home, trying to find a good cat picture.
The size and scope of networks vary. They can be only within businesses/between business and their clients (intranets and extranets), small enough to fit into your house (PANs that govern wireless printers to print cat picture); city-wide (MAN! I would love to see Pittsburgh have one of these); worldwide, so that your mobile carrier can drop your call (GAN), and, of course the Local Area Network, or LAN. LAN is the type of network most Average Joes like me use most frequently. It evolved out of a rapidly increasing use of connected computers in close geographic range (the office, the lab, the educational department, etc), and resulted in a standardization of protocols.
Security issues abound when discussing interconnected computer networks, of course. There is the issue of network security, that (hopefully) prevents unauthorized entities from accessing, modifying, stealing, and otherwise manipulating information. If you've been living under a rock, the issue of network surveillance is very important in this new, interconnected age. Powerful organizations (governments, law enforcement bodies, the Mafia, etc) monitor the data being exchanged over various networks. For safety or nefarious purposes? The debate is wide-spread, heated, and far from over.
Moving on to RFID, and its potential for use in libraries.
Replacing barcodes with RFID chips could speed up library work considerably. I've dragged a squeaking cart loaded down with a laser scanner clumsily connected to an aging laptop through stack after stack to preform inventory. This cumbersome and time-consuming task could optimized with an RFID scanner. Circulation could be optimized by RFID scanners in book drops (some patrons already think this happens, that a book gets checked in immediately after they put it in the drop), checking in/out large stacks of items at once, and having security information encoded onto and RFID for more efficient loss prevention. Self-check out is already in place in many libraries, but it still relies on barcode scanning and (generally) magnetic security screening; trying to teach patrons to "thump" a book after they've checked it out has, in my experience, been a difficult task that leads to library staff (Mary) having to stop them at the door because they've set off the alarms anyway. Streamlining self-checkout might encourage more use, and finally start paying off the exorbitant price of the self-checkout machines. This, however, would make the circulation clerks very lonely.
RFID technology permeates more and more of our world. It is currently more expensive than printing barcodes, but it may be inevitable that libraries will have to move to RFIDs simply because it is the available technology. This presents some problems. The chips are relatively easy to remove or veil, which increases the potential of loss. Smaller items (magazines, thin books, children's books) present challenges for reading individual tags. Replacing tags can become costly in a way that slapping another barcode on an item never will.
Anyway, in case you were wondering:
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