Q. What was the primary focus of QuOnto and Mastro initially?

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Q. Which generation of OBDA systems has focused on efficient rewriting techniques, SQO optimization, and efficient SQL query generation?

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Q. What is a challenge in optimizing query rewriting techniques for industrial applications and Big Data?

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Q. What has been the focus of optimization in the context of OBDA systems so far?

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Q. In the context of Big Data and complex analytical queries, what is considered a viable alternative for achieving good performance?

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Q. What should an OBDA system provide when domain-specific procedures are more efficient?

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Q. What should an optimal system for query answering in the context of Big Data include?

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Q. In the context of OBDA solutions for industrial applications involving time-stamped data, what is one of the requirements for the user query language?

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Q. What is a challenge when using SQL to represent validity of facts with attributes Start and End?

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Q. What is the challenge when only irregular time points are stored for measurements?

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Q. What attribute might refer to the insertion time (transaction time) of a tuple in a time-stamped data scenario?

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Q. What is a potential issue when querying for data in a Big Data scenario with mobile sensors?

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Q. What is the primary distinction between abstract temporal databases and concrete temporal databases?

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Q. What is the difference between valid time and transaction time in the context of temporal databases?

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Q. What is a bitemporal database?

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Q. In the temporal SQL query "SELECT ID, Location, Value FROM Sensor WHERE Start >= 20 and End <= 27," what is the expected result with respect to abstract temporal databases?

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Q. What does the SQL query "SELECT ID, Value, Start, End FROM Sensor WHERE Start <= 23 and End >= 27" retrieve?

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Q. In the context of stream-based query answering, what is the key idea?

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Q. What is the purpose of sliding time windows in stream-based query answering?

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Q. What are temporal aggregation operators used for in stream-based query languages?

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