Y. Edmund Lien

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All eqmvalence is estabhshed between network databases and a subclass of relational databases. A database is a set of files together w~th a set of constraints that the fdes must satisfy. The constraints are spectfied by Bachman diagrams m the network model and by data dependencies m the relational model. The subclass of relatmnal databases of interest ~s(More)
We consider the complexity of several steindard problems for various classes of Pletri nets.. In particular, the reachability problem, the liveness problem and the k-‘boundedness problems are analyzed. Some polynomial time and polynomial space complete probkms for Petri nets are given. We then show that the problem of deciding whether a Petri net Is(More)
I propose a new solution concept–behavioral equilibrium–to study environments with players who are naive, in the sense that they fail to account for the informational content of other players’actions. A behavioral equilibrium requires that: (i) players have no incentives to deviate given their beliefs about the consequences of deviating; (ii) these beliefs(More)
It is shown that a variety of problems have computational complexity equivalent to that of finding a path through a directed graph. These results, which parallel those of Karp at a lower complexity level, concern satisfiability of propositional formulas with two literals per clause, generation of elements by an associative binary operation, solution of(More)
Most database design methods for the relational model produce a flat database, that is, a family of relations with no explicit interrelational connections. The user of a flat database is likely to be unaware of certain interrelational semantics. In contrast, the entity-relationship model provides schema graphs as a description of the database, as well as(More)
  • Y. Edmund Lien
  • Fifth International Conference on Very Large Data…
  • 1979
The role of null values in a relational data base is considered within the framework of multivalued dependencies. When a relation contains null values, a different treatment of data dependencies and different relational operations such as projection and join, are necessary. This paper develops a complete axiomatization for the revised multivalued(More)