Combine or connect: Practical experiences querying library linked data

Linked Data provides a conceptual foundation for creating unified views across Digital Libraries, but implementation challenges must be overcome to realize the vision of computationally assisted cross-corpus research. We report practical experiences comparing two alternative workset building approaches across combined datasets: the HathiTrust Digital Library and the Early English Books Online Text Creation Partnership. In one experiment we combine both datasets within one triplestore using a single ontology and apply consolidated querying; in the other we build two distributed triplestores, each dataset conforming to its own ontology, and connected through federated querying. Each solution presents tradeoffs in complexity, system efficiency and responsiveness, and in the workload of configuring new methods providing access to Digital Libraries. We demonstrate that choosing a consolidated or federated approach fundamentally alters the dataset configuration process for cross-corpora workset building, so should be considered early in deployment specification and design. As both approaches provide equivalent functionality to the end-user, the practice and experience documented here inform design and development of distributed Linked Data Digital Libraries offering combined collection querying.