graphANNIS: A Fast Query Engine for Deeply Annotated Linguistic Corpora

We present graphANNIS, a fast implementation of the established query language AQL for dealing with deeply annotated linguistic corpora. AQL builds on a graph-based abstraction for modeling and exchanging linguistic data, yet all its current implementations use relational databases as storage layer. In contrast, graphANNIS directly implements the ANNIS graph data model in main memory. We show that the vast majority of the AQL functionality can be mapped to the basic operation of finding paths in a graph and present efficient implementations and index structures for this and all other required operations. We compare the performance of graphANNIS with that of the standard SQL-based implementation of AQL, using a workload of more than 3000 real-life queries on a set of 17 open corpora each with a size up to 3 Million tokens, whose annotations range from simple and linear part-of-speech tagging to deeply nested discourse structures. For the entire workload, graphANNIS is more than 40 times faster, and slower in less than 3% of the queries. graphANNIS as well as the workload and corpora used for evaluation are freely available at GitHub and the Zenodo Open Access archive.