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Sequence diagrams are very useful, but UML just adopted a representation that already existed decades before. For example, the original 1981 TCP specification

Sequence diagrams are very useful, but UML just adopted a representation that already existed decades before. For example, the original 1981 TCP specification in RFC 793 [0] has ASCII sequence diagrams (see figures 7 to 14, etc). I don't know if they predate that - less from that era is online - but I wouldn't be surprised. [0] https://www.rfc-editor.org/rfc/rfc793 https://www.rfc-editor.org/rfc/rfc793 Edit: there are a form of sequence diagram in an early FTP specification from 1971: https://www.rfc-editor.org/rfc/rfc172.html https://www.rfc-editor.org/rfc/rfc172.html

esfandia 3y ago
Exactly, UML mostly borrowed from existing representations and its purpose was standardizing semantics and providing some consistency among the diagrams.
Rochus 3y ago
Sequence and activity diagrams were already present in Jacobsons original method, which again is based on the "Ericsson Approach" (originating in 1967), long before UML; they were called interaction diagram and state transition graph.
- cachvico 3y ago
  Who's Jacobson? Google doesn't turn anything up. Neither does "Ericsson Approach" for that matter..
  - agumonkey 3y ago
    This guy https://en.wikipedia.org/wiki/Ivar_Jacobson https://en.wikipedia.org/wiki/Ivar_Jacobson
    - cachvico 3y ago
      Thanks!
  - Rochus 3y ago
    Have a look at e.g. this presentation: https://web.archive.org/web/20060622072014if_/http://www.tcrug.org:80/Documents/PPM02%20final.ppt https://web.archive.org/web/20060622072014if_/http://www.tcr... The state transition graphs of Objectory (Jacobson's method) on the other hand originated in SDL process and procedure diagrams, which were issued in 1976 by CCITT as the Z101 to Z104 recommendations.