Opportunities for Shape-based Optimization of Link Traversal Queries

Data on the web is naturally unindexed and decentralized. Centralizing web data, especially personal data, raises ethical and legal concerns. Yet, compared to centralized query approaches, decentralization-friendly alternatives such as Link Traversal Query Processing (LTQP) are significantly less performant and understood. The two main difficulties of LTQP are the lack of apriori information about data sources and the high number of HTTP requests. Exploring decentralized-friendly ways to document unindexed networks of data sources could lead to solutions to alleviate those difficulties. RDF data shapes are widely used to validate linked data documents, therefore, it is worthwhile to investigate their potential for LTQP optimization. In our work, we built an early version of a source selection algorithm for LTQP using RDF data shape mappings with linked data documents and measured its performance in a realistic setup. In this article, we present our algorithm and early results, thus, opening opportunities for further research for shape-based optimization of link traversal queries. Our initial experiments show that with little maintenance and work from the server, our method can reduce up to 80% the execution time and 97% the number of links traversed during realistic queries. Given our early results and the descriptive power of RDF data shapes it would be worthwhile to investigate non-heuristic-based query planning using RDF shapes.