Some Classes Containing a Fork Algebra Equivalent Variety Involving Projections

  title={Some Classes Containing a Fork Algebra Equivalent Variety Involving Projections},
  author={Juan Eduardo Dur{\'a}n},
  journal={Log. J. IGPL},
Some varieties that are extensions of relational algebras with two constants that play the role of projections are studied. The classes have as a subvariety the abstract fork algebra (AFA) equivalent variety involving projections. They are obtained by weakening some laws valid in AFA. Some applications of the varieties in the literature and in the specification of abstract data types are exhibited. For each of the classes obtained, an answer is given to the question: “Is the relational reduct… 
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