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A Data Resolver Architecture for Discovering Pervasive Data Sources Matthew Denny Database Group U.C. Berkeley Where are the Data Sources in Pervasive Applications? • In traditional applications, the data sources are well defined and reside at well-known locations – SQL tables, web servers, SOAP/RPC apps, etc. • In pervasive applications, neither property holds – Data sources are not at any given location (cell phones emitting diagnostic data roam about) – Data sources may be unreliable (sensors may lose power) – Data sources that are used by one application may use different protocols Data Resolver Needed to Discover Pervasive Data Sources • Data Resolver allows applications to discover data sources • Data Sources send advertisements to the data resolver – Properties: name-value attribute pairs describing the data – Interfaces: descriptions on how to access the data • Applications send specifications to query the data resolver – SQL or LDAP-like queries over the properties • Application may want to know when data sources begin to or no longer match the query – Continuous Queries – Subscriptions to a data source’s advertisements Implementation Plan • Utilize standards for queries and advertisements – WSDL for service descriptions • Scalability Problem: many rapidly updating data sources – Distributed “hybrid P2P” system with partial replication • Each DR Node caches data as specified by its Master DR Node Specification – Any node can accept any ad or query • Publish-Subscribe system used to route ads • Query Containment Indexing (derived from predicate indexing research) used to route specifications