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Feed Your Head at Etech 2003
Pages: 1, 2

Dynamically Connecting Non-Geeks

It's just short of a year since Apple announced Rendezvous, a robust dynamic service discovery mechanism. As Rendezvous architect Stuart Cheshire describes it, the technology is quite straight forward. The big idea is that the industry has settled on IP to connect devices over wide area networks. For more local connections, however, we have a sea of protocols. The two questions Cheshire asks the audience are, "Why not settle on a single protocol?" and "Why not settle on the same protocol we use in wide area networks?"



Accepting that premise, there are a few issues that need to be resolved. First, when you use IP you either have a dedicated IP address that has been assigned to your device or you use DHCP. On a local network you would like to remove the requirement of DHCP. The strategy is self-assigned, link-local addressing. Choose any IP address in a range set aside for this purpose. Ask if anyone else on your local network is using that address. If not, then that is your address. If someone else is already using it, choose another address and try again.

The second issue is naming. You don't want end users to have to use IP addresses to locate services. A more user friendly solution is human readable names. There is no DNS server to resolve names to the IP address that was self-assigned in the last step. The solution is similar. Pick a desired name in the .local subdomain. Issue a query to see if someone else is already using it. If so, pick another. If not, the name is yours.


Stuart Cheshire's Rendezvous talk was right in step with the laptop toting, wireless networking audience.

If names are self-assigned and IP addresses are self-assigned, then the next step is to support browsing so that you can locate the services you are looking for. Devices already need to implement mDNS, so Rendezvous uses standard DNS capabilities to identify services. Cheshire offers an example of searching for a printer by issuing a DNS Query to find a device that supports ipp (the Internet Printer Protocol): _ipp._tcp.local.PTR ? . You will get back a list of records and the first part of each name you get back is the user friendly name for that service.

Cheshire presents three demos. He connects a netcam. Because he happens to know the name of the netcam he is able to type its .local name into his browser and with no configuration the camera's output is displayed in the browser. As a second demo he connects a Brother printer with the Rendezvous services browser open and as soon as the printer comes to life it announces itself to the network and is visible in the browser under available printers. Cheshire remarks that Rendezvous has many of the ease of use features of AppleTalk while resolving some of the limitations and while depending on widely adopted standards.

As a third demo, Cheshire started the Hydra application and opened a document. Within moments, half a dozen audience members had started up their versions of Hydra and connected to his document. While he returned to his presentation, those of us with Hydra continued to create and edit a document in parallel. One person uploaded an ASCII image of a face. Another person added a pupil to one eye and a different person added a matching pupil to the other eye. Emerging networks. Collaborating communities. The whole is much greater than the sum of the parts.

Kay Issues a Challenge

Tim O'Reilly introduces Alan Kay to the morning keynote audience with a Kay quote that "it is easier to invent the future than to predict it." Kay cautions that his talk begins with a bit of complaining, but says that the last 20 years have been pretty boring in the world of computing. Given the glimpses into the future that we're getting, that doesn't sit well with the audience. Kay says that the problem is that after personal computers got commercialized, a lot of vendors targeted businesses and businesses aren't that creative about using any tools. Businesses are prime examples of learning a system and sticking with it.

Kay's first principle is sticking with children. He asserts that most people are instrumental reasoners. Their judgment of any tool or idea is seen in terms of the current goal structure. Kay says "adults basically have too much context. Many things work pretty well and pretty well is the enemy of qualitative improvement and vice verse."


"It is easier to invent the future than to predict it," Alan Kay

For those who are pretty satisfied with the current state of software, Kay showed movies of applications from forty years ago. He showed a demo of Sketchpad from 1963. Ivan Sutherland looked at an awful display and asked the critical question, "What else can it do?" He ended up creating an object oriented system that could be used easily for prototyping and along the way invented computer graphics. Kay continues his history lesson with example after example of applications that ran well over thirty years ago on constrained computing devices and displays and were responsive and innovative.

Kay next demonstrates some of the work he is doing with children and Squeak. He shows how easy it is to design a car and give it behavior. He then quickly sketches a steering wheel and connects the car to the steering wheel so that he can use the steering wheel to control the car. Kay walks through an example of children exploring the acceleration of an object due to gravity. Students film an object falling and pull out every fifth frame. They use objects to measure the changes in velocity as the object falls and then create a model of a falling object that they run side by side with the original video to verify their model.

Kay and David Smith demonstrate Croquet, an immersive three dimensional world. Kay describes this as a broadband conference call. Using p2p everything one does is shared and replicated. As Kay navigates around the space his character comes in and out of Smith's view. They interact with each other and with the space. When one of them creates a fish that he introduces into the world, the other sees the same fish and both can follow its movement. This is the modern day incarnation of Kay's Vivarium project. Imagine a Rendezvous enabled Croquet. At next year's ETech, attendees could be navigating a common virtual space in addition to instant messaging each other.

Just Hanging Out

It's no secret that when groups of people come together to hear interesting presentations, the greatest value is usually derived from unscheduled conversations. A group that forms to share a power strip is soon talking and sharing ideas and finding common interests. Two or more people find themselves grabbing a cup of coffee or sitting at the bar comparing notes from the outstanding talks of the day. Speakers come to these conferences expecting to interact with other attendees. Everyone is generous with their time and ideas. From the skeleton of the scheduled conference, the full conference emerges.

Three people heading off to dinner soon came a dozen (Bunnie meet Possum, Possum this is Bunnie). Conversation starts with Bunnie Huang's cool tutorial on Hardware Hacks where the dinner party began to form. Soon the conversation turns to the DMCA and what sort of hacks are legal. Tim O'Reilly and Cory Doctorow argue the implications of DRM in the light of the DMCA with those seated in between looking from one to the other like the audience at a tennis match.


Greg Olin (left) chats with Brent Simmons and James Duncan Davidson at the Mac OS X Innovators reception sponsored by Apple Developer Connection.

At the reception for the Mac OS X Innovator Contest awards, Dan Wood, creator of Watson, stops over to talk to Brent Simmons who has just won the award for his NetNewsWire application. James Duncan Davidson and Greg Olin banter ideas back and forth about applications they are working on. Greg organizes an impromptu strategy session with James and Brent to further the discussion. Robb Beal, the creator of Spring, who placed second in the contest joins the conversation. Spring, Watson, NetNewswire each are individually important applications created by single developers. Taken together (and they can be purchased as a bundle) they change your relationship to the Internet from being just browser driven.

There were plenty of leftovers that could have been packed, but they would have just sat in some note on a laptop--the metaphorical refrigerator. By the time they would have been remembered they would be showing signs of age and other more recent leftovers would have been stored away as well. You just have to trust that collectively, nothing will go to waste. Someone else will take home the yams and the stuffing. Just a little turkey and perhaps some cranberry bread.

Daniel H. Steinberg is the editor for the new series of Mac Developer titles for the Pragmatic Programmers. He writes feature articles for Apple's ADC web site and is a regular contributor to Mac Devcenter. He has presented at Apple's Worldwide Developer Conference, MacWorld, MacHack and other Mac developer conferences.


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