An increasing number of (semantic) web applications store a very large number of (subject,predicate,object) triples in specialized storage engines called triple-stores. Often, triple-stores are used mainly as plain data stores, i.e., for inserting and retrieving large amounts of triples, but not using more advanced features such as logical inference, etc. However, current triple-stores are not optimized for such bulk operations. This paper presents 3XL, a triple-store that efficiently supports bulk operations on very large amounts of triples. The distinguishing features of 3XL include a) using object-relational DBMS features such as inheritance, b) using specialized data-dependent schemas (intelligent partitioning), c) extensive use of bulk-loading techniques, and d) efficient use of main memory. 3XL supports both efficient loading as well as efficent query operations, especially when the subject and/or predicate is known. Extensive experiments with a PostgreSQL-based implementation show that 3XL outperforms existing DBMS-based triplestores.
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