Declarative expression of deductive database updates
PODS '89 Proceedings of the eighth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Hypothetical datalog negation and linear recursion
PODS '89 Proceedings of the eighth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
A language for legal Discourse I. basic features
ICAIL '89 Proceedings of the 2nd international conference on Artificial intelligence and law
PODS '92 Proceedings of the eleventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Foundations of semantic web databases
PODS '04 Proceedings of the twenty-third ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
| Hi-index | 0.00 |
We present an extension of Horn-clause logic which can hypothetically add and delete tuples from a database. Such logics have been discussed in the literature, but their complexities and expressibilities have remained an open question. This paper examines two such logics in the function-free, predicate case. It is shown, in particular, that augmenting Horn-clause logic with hypothetical addition increases its data-complexity from PTIME to PSPACE. When deletions are added as well, complexity increases again, to EXPTIME. To establish expressibility, we augment the logic with negation-by-failure and view it as a query language for relational databases. The logic of hypothetical additions then expresses all database queries which are computable in PSPACE. When deletions are included, the logic expresses all database queries computable in EXPTIME.