eng
Schloss Dagstuhl – Leibniz-Zentrum für Informatik
Leibniz International Proceedings in Informatics
1868-8969
2018-03-05
10:1
10:17
10.4230/LIPIcs.ICDT.2018.10
article
On the Expressive Power of Query Languages for Matrices
Brijder, Robert
Geerts, Floris
Van den Bussche, Jan
Weerwag, Timmy
We investigate the expressive power of MATLANG, a formal language for matrix manipulation based on common matrix operations and linear algebra. The language can be extended with the operation inv of inverting a matrix. In MATLANG + inv we can compute the transitive closure of directed graphs, whereas we show that this is not possible without inversion. Indeed we show that the basic language can be simulated in the relational algebra with arithmetic operations, grouping, and summation. We also consider an operation eigen for diagonalizing a matrix, which is defined so that different eigenvectors returned for a same eigenvalue are orthogonal. We show that inv can be expressed in MATLANG + eigen. We put forward the open question whether there are boolean queries about matrices, or generic queries about graphs, expressible in MATLANG + eigen but not in MATLANG + inv. The evaluation problem for MATLANG + eigen is shown to be complete for the complexity class Exists R.
https://drops.dagstuhl.de/storage/00lipics/lipics-vol098-icdt2018/LIPIcs.ICDT.2018.10/LIPIcs.ICDT.2018.10.pdf
matrix query languages
relational algebra with aggregates
query evaluation problem
graph queries