1. Open Hypermedia
: hypertext features present within whole environment
- Links and anchors must be kept separately from documents
- Linkbases and Link Services
https://smartbear.com/learn/api-design/what-is-hypermedia/
2. Dexter Hypertext Reference Model
: formal model of an open hypertext system, developed 1988-1990
1. Run-Time Layer: Presentation; user interaction; dynamics
1-1. Presentation Specification
2. Storage Layer: database of nodes and links
2-1. Anchoring
3. Whithin-Component Layer: content/structure inside nodes
http://www.cyberartsweb.org/cpace/ht/christanto/dexter_model.htm
3. Hyper-G
: a publishing system with hypertext features more advanced than those available with HTTP and web browser
- Client-Server architecture
- Persistent session connections
- First class nodes, links and anchors
- Bi-directional links
- Link integrity: Hyper-G tries to maintain link such that user is always able to follow any link that is presented to them
* Compared with the Web: if the destination of a link goes away, the user sees 404 Not Found
* The endpoint of a link (source or destination) needs to define a node
* The Dangling Link Problem: if the endpoint refers to an invalid node then we have a dangling endpoint (link)
* The Content Reference Problem: if the endpoint refers to the wrong part of the node content then we have a content reference problem
- A notion of composites/collections
(+) Authoring support integrated into browser, and designed into protocols from outset
(+) Early support for multimedia
(-) Own internet protocol (HG-CSP) / markup language (HTF) / browser (Harmony)
http://whatis.techtarget.com/definition/Hyper-G
http://stackoverflow.com/questions/32039568/what-are-the-integrity-and-crossorigin-attribute
4. Microcosm
: originally designed for use with read-only media, as a desktop-based system, later expanded to a distributed system
- Specific, Local and Generic Links
* Source anchor of a link is not embedded in the source document, but its position(s) is described in the linkbase
(+) Rich model of linking (generic links, n-ary links, etc)
(+) Integration with third-party application
(-) Scalability
(-) Arguably, no native document format
(-) No support for link integrity
https://www.youtube.com/watch?v=DF9oAwUgmKo
5. Open Hypermedia Protocol
: initially a naive attempt to "shim" existing linkservers so hat they could be used by standard client integrations
- Fundamental Open Hypermedia Model (FOHM): OHP forms the basis for later integration efforts
- Location Specifiers (LocSpecs): used to indicate anchor positions
(+) A formalised version of the data model (FOHM) is widely used in the community
(-) The shim architecture was naive and was replaced by middleware
(-) The message overhead is very high
http://users.ecs.soton.ac.uk/hcd/protweb.htm
6. Open Hypertext on the Web
: If Microcosm and Hyper-G were so good, why are we not all using them?
* We lose the goal of hypertext across the entire desktop
* HTML/DOM (and browsers) do not allow easy control of anchor positions
- Linkbase Creation : Theming technology extracts key phrases from documents based on location and frequency
- Link Injection: Links can be added at different times in the document retrieval process
* batch process documents: generate static HTMLl pages
* on demand by web server: careful choice of data structures and algorithms
* in proxy server: user configures their browser to proxy through the link injector
* in browser: with a plugin that fetches links and rewrites documents
- Link Presentation: Links can be rendered to distinguish from authored links
(+) Applications do not have to be responsible for maintaining "foreign" markup
(+) You can tailor your linkbases to your nodes (contexts)
(+) On read-only media, keeping links separately is the only way to do it!
(-) Keeping link separately introduces potentially consistency issues
(-) For streaming, data links as well as data have to be synchronised
http://webaim.org/techniques/hypertext/hypertext_links
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