A. Cortesi, A. Dovier, E. Quintarelli, and L. Tanca.
Operational and abstract semantics of the query language G-log.
Theoretical Computer Science, 275/1-2 pp 521-560, 28 March 2002.
we have analyzed the existing graphical query language G-log. Since DB instances (even web sites) are (labeled) graphs and in G-log queries are exactly graphs, it can be shown that retrieving information amounts to finding subgraphs of the instances that "matches" the query graph. In this paper we have shown that the bisimulation test is what really needed for implementing the "matching" test. The results are for the language G-log but are immediately applicable to any language that deals with "graph-based" DBs.
A. Dovier, C. Piazza, and A. Policriti.
An Efficient Algorithm for Computing Bisimulation Equivalence.
Theoretical Computer Science 311(1-3):221-256, 2004.
we show that the bisimulation test can be computed in O(E log N) or even in O(E + N) if the graphs are acyclic or in some other, well-characterized, cases.
A. Dovier and C. Piazza.
The Subgraph Bisimulation Problem.
IEEE Transaction on Knowledge and Data Engineering, vol 15, n. 4, 2003.
A. Dovier and E. Quintarelli.
Model Checking Based Data Retrieval.
In Proc. of Database Programming Languages,8th International Workshop on Databases and Programming Languages, DBPL 2001, Revised Papers. LNCS 2397, pages. 62--77. Springer 2002.
we have shown how most typical DB queries can be naturally encoded into CTL formulas and therefore that the query retrieval activity is equivalent to solving the model checking problem. For CTL, it can be solved in time LINEAR wrt the product of the size of the graph (DB) and the size of the query (the CTL formula). With these ideas, extracting information from Web-Databases becomes feasible and, moreover, we can also have a purely logical characterization of this activity.
Agostino Dovier and Elisa Quintarelli.
Applying Model-Checking to solve Queries on Semistructured Data
Computer Languages, Systems & Structures.. 25 (2009) pp. 143-172.