BB-Graph: A New Subgraph Isomorphism Algorithm for Efficiently Querying Big Graph Databases

With the emergence of the big data concept, the big graph database model has become very popular since it provides strong modeling for complex applications and fast querying, especially for the cases that require costly join operations in RDBMs. However, it is a big challenge to find all exact matches of a query graph in a big graph database, which is known as the subgraph isomorphism problem. Although a number of related studies exist in literature, there is need for a better algorithm that works efficiently for all types of queries since the subgraph isomorphism problem is NP-hard. The current subgraph isomorphism approaches have been built on Ullmann's idea of focusing on the strategy of pruning out the irrelevant candidates. Nevertheless, for some graph databases and queries, the existing pruning techniques are not adequate to handle some of the complex queries. Moreover, many of those existing algorithms need large indices that cause extra memory consumption. Motivated by these, we introduce a new subgraph isomorphism algorithm, namely BB-Graph, for querying big graph databases in an efficient manner without requiring a large data structure to be stored in main memory. We test and compare our proposed BB-Graph algorithm with two popular existing ones, GraphQL and Cypher of Neo4j. Our experiments are done on a very big graph database application (Population Database) and the publicly available World Cup graph database application. We show that our algorithm performs better than those that we use for comparison in this study, for most of the query types.