  Intro
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 Boulevard of Broken Songs
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Admin
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Follow-up
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Big Concepts
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"Meta-Data"
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Response-Request Paradigm
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Separation of Code, Data and Presentation
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Less confusion
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Better caching
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More efficiency
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AJAX
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Asynchronous Java and XML
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Original article where it appeared
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New Web User Interface paradigm
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Web 2.0
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Theory
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Rich Client technology
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Rich and Client
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Rich HCI
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Spreadsheet
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edit data in place
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edit with keyboard and mouse
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drag and drop
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feedback
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cursor changed
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text was highlighted
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rich interactivity
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Client
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Interacts with a remote process
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Basic Web Page
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Amazon.com
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Complicated features, but all backend
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Hyperlink/text form interaction
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If I didn't do anything for a week the page wouldn't change
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even if the inventory changed
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new books arrived etc.
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Lists don't move between pages
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Why are web pages like this?
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Network Latency
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remote and local procedure calls are not the same thing
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Abstractions for remote procedure calls look good but are slow
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Draw the local model
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calling function -> model -> local memory
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Draw the connection diagram
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Local model, serialization, application protocol, physical transport, application protocol, selialization, remote model and back
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Network calls have more overhead
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But, it is variable and hard to predict
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It will always be worse then a local call
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Impact on usability
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slight delays are *really* annoying, *distracting*
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the promise of ubicomp
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desktop application bad usability design makes the application feel buggy, but in a networked application it is free.
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Asynchronous Interaction Example
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Sleeping Child, make coffee, feed cat
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Synchronous interaction
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Parallel to U/I
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because of network any remote call should be treated asynchronously
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old model caused web pages to hang when network latency was there
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Unfortunately HTTP is request/response
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Classic web design won't work
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bult around concept of "pages"
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Why does this work for Amazon
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Usage Patterns :Transient Usage or Sovereign Usage
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transient
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short bursty usage
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sovereign application
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runs for hours on end, primary user focus
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examples of both?
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Transient
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amazon,ebay, original google
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to what degree is your UI "visible"
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page-based solutions are good enough for transient but not sovereing apps
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AJAX is Unlearning the web
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browser hosts an application, not content
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every page is new content vs. request for data
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server functionality is moved to browser
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example, the shopping basket is in the client
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draw picture of login logout web pages model
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include browser, server, login, pages
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draw picture of client application picture
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include client application and data model
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server delivers data not content
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Draw graph of network resources
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classic web app (data, presentation, content)
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AJAX web app (logic, presentation, data)
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bandwidth usage over time
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User interaction with the application can be fluid and continuous
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Typically when a page is submitting data, the user is in limbo
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Use the shopping cart example
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This is real coding
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Examples
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google suggest
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bus monster
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AJAX alternatives
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Flash
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Java Web Start
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Why might one technology be pushed over another?
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