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Hypertext and E-Commerce

Hypertext and E-Commerce. Informatics 211 November 6, 2007. The Basics of Hypertext. The concept: interrelated information Content (the information) Structure (the links between the information) View (what part of the content and structure one sees at a given moment). Content.

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Hypertext and E-Commerce

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  1. Hypertext and E-Commerce Informatics 211 November 6, 2007

  2. The Basics of Hypertext • The concept: interrelated information • Content (the information) • Structure (the links between the information) • View (what part of the content and structure one sees at a given moment)

  3. Content • Homogeneous or heterogeneous? • Homogeneity gives lots of scope for storage mechanisms, optimizations, complex queries, … • Heterogeneity is what makes hypertext useful, and different from databases • The subtle notion of “objects”

  4. Structure • Links • Implicit, computed, explicit • Anchors • On what? The “object”? Part of the object? What about dynamic objects? Only certain types of objects? • Links on links. Or rather, links between anchors on links?

  5. View and Interactivity : where the user is at runtime, interacting with the information • Distinguishing content and structure • Distinguishing views of objects from the objects. • Anchors on the views, rather than the objects • Traversal, context, the hypertext state machine • What does a link mean? • The assumption of "take me there and show me" • How many users are there? • Who is the user? Hypertext and automated analyses

  6. Architecture • Where's the data? Who controls it? Who can change it? Who can see it? • Where are the links? • Who controls the viewing? • Who controls the state transitions?

  7. Classic systems • KMS, Notecards, Hypercard • Chapter 5 from Jakob Nielsen's book Multimedia and Hypertext: The Internet and Beyond, Morgan Kaufmann Publishers, 1995. • http://www.useit.com/papers/hypertext_theory/

  8. Open Hypertext: bringing hypertext to other applications • Open: • link to external applications (and data that they control) • link from external applications? • First-class links and the link base • n-ary links

  9. Chimera example

  10. Chimera Architecture

  11. Dynamic links & content • Links whose existence are determined at run time • Database driven queries • Content cobbled together

  12. Architecture • data not under a single authority regime • viewing not under a single regime • what about the link base?

  13. The World Wide Web • Naming the information • Heterogeneous sources, and hence a communication protocol • Architecture • client-server • Roy’s dissertation defense slides

  14. Hybrid Approaches • Chimera 2.0

  15. Bridge to Andre’s Talk • WebDAV: an extension to the HTTP/1.1 protocol to support • Distributed • Authoring And • Versioning • But have to wait until we’ve covered the background (at least)

  16. REST Principles • 1. The key abstraction of information is a resource, named by an URL. • 2. The representation of a resource is a sequence of bytes, plus representation metadata to describe those bytes. • 3. All interactions are context-free. • 4. Only a few primitive operations are available. • 5. Idempotent operations and representation metadata are encouraged in support of caching. • 6. The presence of intermediaries is promoted.

  17. Insights on the Web • Separation of representation from resource (cf. node/object in hypertext) • Tolerance of inconsistency • Broken links • Unintelligible representations • Best effort processing • Decentralization and network effects • URIs as plain text

  18. E-Commerce • The demands of financial security • The demands of the user experience • Session IDs: maintaining pointers to an individual across time • Shopping carts • The demands of an extensive set of offerings • Dynamic page construction • The example of Amazon.com

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