Abstract : To combine and query ordered data from multiple sources, one needs to handle uncertainty about the possible orderings. Examples of such “order-incomplete” data include integrated event sequences such as log entries; lists of properties (e.g., hotels and restaurants) ranked by an unknown function reflecting relevance or customer ratings; and documents edited concurrently with an uncertain order on edits. This paper introduces a query language for order-incomplete data, based on the positive relational algebra with order-aware accumulation. We use partial orders to represent order-incomplete data, and study possible and certain answers for queries in this context. We show that these problems are respectively NP-complete and coNP-complete, but identify many tractable cases depending on the query operators or input partial orders.
https://hal.inria.fr/hal-01570603
Contributor : Pierre Senellart
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Submitted on : Monday, July 31, 2017 - 12:20:05 PM
Last modification on : Monday, March 25, 2019 - 5:18:07 PM
Antoine Amarilli, Mouhamadou Lamine Ba, Daniel Deutch, Pierre Senellart. Possible and Certain Answers for Queries over Order-Incomplete Data. 24th International Symposium on Temporal Representation and Reasoning (TIME 2017), Oct 2017, Mons, Belgium. pp.4:1-4:19, ⟨10.4230/LIPIcs.TIME.2017.4⟩. ⟨hal-01570603⟩
