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 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.