@Article{Kahl-1999d,
  author = 	 {Wolfram Kahl},
  title = 	 {Relational Matching for Graphical Calculi of Relations},
  journal = 	 {Journal of Information Science},
  year = 	 {1999},
  volume = 	 {119},
  number = 	 {3--4},
  month = 	 DEC,
  pages = 	 {253--273},
  URL = {http://www.elsevier.com/gej-ng//10/23/143/47/27/33/abstract.html},
  abstract = {In this paper we extend an earlier approach to
              graphical relation calculi towards relational matching,
              thus allowing proofs with fewer auxiliary steps and
              concentrating more on the essential proof ideas.

              For facilitating the formal argument we introduce
              hierarchical relational diagrams as an
              intermediate structure and employ more of the
              algebraic graph rewriting repertoire for defining
              relational rewriting of these hierarchical diagrams.}
}