Deltal lenses and opfibrations

Michael Johnson, Robert Rosebrugh

Research output: Contribution to journalConference paperpeer-review

21 Citations (Scopus)


We compare the delta lenses, also known as d-lenses, of Diskin et al. with the c-lenses, known to be equivalent to opfibrations, already studied by the authors. Contrary to expectation a c-lens is a d-lens but not conversely. This result is surprising because d-lenses appear to provide the same information as c-lenses, and some more besides, suggesting that the implication would be the reverse -- a d-lens would appear to be a special kind of c-lens. The source of the surprise can be traced to the way the two concepts deal differently with morphisms in a certain base comma category (G,1V). Both c-lenses and d-lenses are important because they extend the notion of lens to take account of the information available in known transitions between states and this has important implications in practice.
Original languageEnglish
Pages (from-to)1-18
Number of pages18
JournalProceedings of the Second International Workshop on Bidirectional Transformations : BX 2013
Publication statusPublished - 2013
EventInternational Workshop on Bidirectional Transformations (2nd : 2013) - Rome, Italy
Duration: 17 Mar 201317 Mar 2013


  • Delta lens
  • opfibration
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