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We study the query answering using views (QAV) problem for tree pattern queries. Given a query and a view, the QAV problem is traditionally formulated in two ways: (i) find an equivalent rewriting of the query using only the view, or (ii) find a maximal contained rewriting using only the view. The former is appropriate for classical query optimization and(More)
Moving object databases (MOD) have gained much interest in recent years due to the advances in mobile communications and positioning technologies. Study of MOD can reveal useful information (e.g., traffic patterns and congestion trends) that can be used in applications for the common benefit. In order to mine and/or analyze the data, MOD must be published,(More)
XPath and XQuery (which includes XPath as a sublanguage) are the major query languages for XML. An important issue arising in efficient evaluation of queries expressed in these languages is satisfiability, i.e., whether there exists a database, consistent with the schema if one is available, on which the query has a non-empty answer. Our experience shows(More)
Motivated by the "database-as-service" paradigm wherein data owned by a client is hosted on a third-party server, there is significant interest in secure query evaluation over encrypted databases. We consider this problem for XML databases. We consider an attack model where the attacker may possess exact knowledge about the domain values and their(More)
To support privacy-aware management of data in social spaces, the user personal data needs to be stored at each user device, and shared only with a trusted subset of other users. To date, social spaces only have fairly limited access control capabilities, that do not protect the possibly sensitive data of the users. In this demonstration, we showcase our(More)
—Spurred by developments such as cloud computing, there has been considerable recent interest in the paradigm of data mining-as-a-service. A company (data owner) lacking in expertise or computational resources can outsource its mining needs to a third party service provider (server). However, both the items and the association rules of the outsourced(More)
As wireless networks become more pervasive, the amount of the wireless data is rapidly increasing. One of the biggest challenges is how to store these data. To address this challenge, distributed data storage in wireless networks has attracted much attention recently, as it has major advantages over centralized approaches. To support the widespread adoption(More)
Recent years have witnessed pervasive use of location-aware devices such as GSM mobile phones, GPS-enabled PDAs, location sensors, and active RFID tags. The use of these devices generates a huge collection of spatio-temporal data, variously called moving object data, trajectory data, or moblity data. These data can be used for various data analysis purposes(More)
Answering queries using views is a well-established technique in databases. In this context, two outstanding problems can be formulated. The first one consists in deciding whether a query can be answered exclusively using one or multiple materialized views. Given the many alternative ways to compute the query from the materialized views, the second problem(More)