TAPSOFT '89 is the Third International Joint Conference on Theory and Practice of Software Development held in Barcelona, Spain, March 13-17, 1989. The conference consisted of three parts: - Advanced Seminar on Foundations of Innovative Software Development - Colloquium on Trees in Algebra and Programming (CAAP '89) - Colloquium on Current Issues in Programming Languages (CCIPL) The TAPSOFT '89 Conference Proceedings are published in two volumes. The first volume includes the papers from CAAP plus the more theoretical ones of the invited papers. The second volume comprises the papers from CCIPL and the invited papers more relevant to current issues in programming languages.

Inhalt
The varieties of programming language.- Independence of negative constraints.- Completion procedures as transition rules + control.- A modular framework for specification and implementation.- On the existence of initial models for partial (higher-order) conditional specifications.- Terms and infinite trees as monads over a signature.- The subsequence graph of a text.- Syntactical properties of unbounded nets of processors.- Shuffle equations, parallel transition systems and equational Petri nets.- Towards a lambda-calculus for concurrent and communicating systems.- A distributed, net oriented semantics for Delta Prolog.- Continuation semantics for PROLOG with cut.- Labeled trees and relations on generating functions.- Proofs of declarative properties of logic programs.- The reachability problem for ground TRS and some extensions.- Order-sorted completion: The many-sorted way.- Algebraization and integrity constraints for an extended entity-relationship approach.- Decidable boundedness problems for hyperedge-replacement graph grammars.- Implementation of parameterized observational specifications.- Priority controlled incremental attribute evaluation in attributed graph grammars.- Some applications and techniques for generating functions.- Semi-constructive formal systems and axiomatization of abstract data types.- Inductive proofs by resolution and paramodulation.- Local model checking in the modal mu-calculus.