◆ Semantic Web Catalogue

Problem thread

One-way or two-way links

Should a link be a cheap one-way pointer that can break, or a maintained two-way relationship?

issue
linking
status
reopened
steps
7, 1945–2018
threads
all problem threads

Early hypertext designs, above all Ted Nelson's Xanadu, wanted links that both ends know about and that never break. The Web chose one-way links that anyone can make without asking, and Berners-Lee later described that as trading consistency for scalability. The cost shows in link rot. Webmention brought a way back: a site can be told when someone links to it.

Lineage

  1. Jul 1945
    precedent writing ★ seminal
    As We May Think

    Imagines the memex, a desk for storing records and linking them by association, so that a reader can build and share trails between documents. [src]

  2. 1960
    proposes project ★ seminal
    Project Xanadu

    Links are visible and can be followed from all endpoints, and documents can include parts of others by reference (transclusion). Only partial systems were released: Udanax in 1998, OpenXanadu in 2014. [src]

  3. 1965
    proposes writing ★ seminal
    A File Structure for the Complex, the Changing and the Indeterminate

    Introduces the word 'hypertext' in print, for a file structure that holds documents that change and link to one another. [src]

  4. 1990
    settles project ★ seminal
    World Wide Web

    Links are one-way: a page can link anywhere without the target knowing or agreeing, and a link can break. Berners-Lee later called this the decision to make links monodirectional, 'sacrificing consistency for scalability'. [src]

  5. 26 Dec 2014
    measures writing ★ seminal
    Scholarly Context Not Found: One in Five Articles Suffers from Reference Rot

    The cost of links that can break: about one in five scholarly articles cites web resources that have since vanished or changed. [src]

  6. 12 Jan 2017
    reopens standard
    Webmention
    ↳ responds to World Wide Web

    A way to notify any URL when you mention it. The receiver fetches the source and checks that it really links to the target, so a page can show who links to it without a central index. [src1][src2]

  7. 23 Jan 2018
    proposes standard ★ seminal
    ActivityPub

    In the Fediverse a reply names the post it answers and is delivered to the original author's inbox, so links between servers come with a notification back. [src]

Recent signals

Dated events that show the problem moving, newest last.

  1. 17 May 2024

    Pew finds 38% of web pages that existed in 2013 no longer load, and a quarter of all pages seen between 2013 and 2023 are gone.[src]

Open now

Under each question, the answers people have put forward or built. The catalogue gives no odds on them.

  • How can a site show who links to it without being flooded with spam? [src]
    Webmention requires receivers to verify each mention and allows them to moderate before publishing.
    • The receiving site verifies each mention and moderates what it shows. Webmention
      Webmention has the receiver check that the source really links to it; dealing with spam is left to the receiver.[src]
    • All records are public, so anyone can index who links to what. AT Protocol
      In AT Protocol every post is a public record in a repository, which indexers collect to show replies and links.[src]
  • Can a link keep pointing at what was cited after the target changes? [src1][src2]
    Xanadu's links and transclusions were meant to survive edits; on the Web, cited pages often change or vanish.
    • Archive the page when you cite it, and link to both. Wayback Machine
      The Wayback Machine keeps copies that a citation can point to as well as the live page.[src]

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