Peer Data Management Systems Concepts and Approaches

Transcription

1 Peer Data Management Systems Concepts and Approaches Armin Roth HPI, Potsdam, Germany Nov. 10, 2010 Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

2 Agenda 1 Large-scale Information Sharing 2 PDMS Architecture 3 System Characteristics 4 Comparison of Approaches 5 Conclusion + Future Research Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

3 Large-scale Information Sharing Large-scale Information Sharing Regional hospital north Red cross capital headquarters Medication logistics company Government control center National medication inventory Capital hospital Capital medication inventory National pharmacies association Medicine company Medicines sans fronties national base Regional hospital east Regional hospital south Peer Peer schema Peer data Peer mapping Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

4 PDMS PDMS Architecture Heterogeneity Peer Autonomy Mediator: Queries passed to neighbors Flexibility High Redundancy Information Loss Regional Red cross hospital capital north headquarters Government control National center medication inventory Capital medication inventory Capital hospital National pharmacies association Medication logistics company Medicines sans fronties Medicine national base company Regional hospital east Peer Regional Peer schema hospital Peer data south Peer mapping Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

5 PDMS Architecture Distributed Information Systems Distributed DBMS Distribution P2P System PDMS DBMS Data Warehouse Heterogeneity Autonomy Mediator-based Information System Federated DBMS [OV99] Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

6 PDMS Architecture General System Model PDMS set P of peers P i with P i = {G i, S i, L i, M i }: Peer schema G i Local schema S i Local mappings L i Peer mappings M i Peer mappings m M i M j are assertions φ Gi φ Gj resp. φ Gj φ Gi with queries φ Gi and φ Gj of different arity P i P j L G i i S i M i /M j L j G j S j Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

7 PDMS Architecture Peer Mappings Different peers P i, P j heterogeneous in Data model Schema Query language Data schema interplay [BCHL05] Intens./extens. completeness Language of mapping assertions φ Gi φ Gj must bridge all these types of heterogeneity [MBDH02] Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

8 Example Example PDMS Architecture Global-as-view Mapping P 1 R 1 a b c d e 20 #tuples R 5 (a,b,c,d,e) R 1 (a,b,c,d,e), b = 'US' Source R 2 (a,b,c), R 3 (c,d,e) R 1 (a,b,c,d,e) P 5 R 5 a b c d e 90 P 2 Local-asview 60 Mapping R 4 (a,b,c,d) R 2 (a,b,c), R 3 (c,d,e), d > 1 R 2 a b c R 3 c d e 60 R 6 (c,d,e) R 3 (c,d,e), d > 10 R 6 c d e R 4 P 6 P c d e 4 10 R 5 (a,b,c,d,e) R 6 (c,d,e) 9 Armin Roth Paris, July 13, 2010 Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

9 PDMS Architecture Semantics of PDMS Query Answering [CGLR04] Special case: all queries in mapping assertions CQ Semantics of an individual peer: FOL theory T Pi (Global) source database D Set of all models of PDMS P wrt. D: sem D (P) = { I I is a model of all T Pi based on D I satisfies all M i } Meaning of I satisfying M i varies in different approaches for peer mappings Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

10 PDMS Architecture Applications for PDMS Fusion of organisations Semantic Web [HIMT03, HHNR05] Disaster Management [HIST03] Groupware [ANR07] In general: Large, loosely coupled integrated information systems Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

11 System Characteristics System Model [HRZ + 08] Category Data model Topology Mapping language Possible Alternatives Relational XML (incl. web services) RDF Arbitrary Arbitrary without cycles GLaV Subset of FOL Mapping tables Data schema interplay (e.g., HePToX) Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

12 Semantics System Characteristics Expressiveness and interpretation of mapping language determines semantics of query answering data exchange 2 principal approaches 1 Global reasoning: Mappings are interpreted as material logical implication 2 Local reasoning: Only exchange of certain answers Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

13 System Characteristics Autonomy/Modularity Important category in distributed systems with many stakeholders Types: Design autonomy (modeling, naming) Communication autonomy (decide about cooperations) Execution autonomy (scheduling of requests) Influenced by Semantics Functional requirements (e.g., update propagation, global catalog) Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

14 Piazza [HIST03] Comparison of Approaches Data model Mapping language Query language Peer autonomy Semantics of query answering Query optimization Relational, XML GLaV, definitional mappings CQ Global catalog Open-world wrt. certain peer Containment-based pruning at query planning time Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

15 Comparison of Approaches Hyper [CGL + 04, CGLR04] Data model Mapping language Query language Peer autonomy Semantics of query answering Query optimization Other Relational GLaV CQ Preserved Based on epistemic logic, exchange of certain answers none Inconsistency tolerance Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

16 Comparison of Approaches Hyperion [AKK + 03, KAM03] Data model Mapping language Query language Peer autonomy Semantics of query answering Query optimization Other Relational (others also possible) Generalization of GLaV CQ, value search Preserved Open-world and closed-world possible unknown Update propagation Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

17 Comparison of Approaches Hyperion Highly dynamic and scalable Schema mapping expressions Mapping tables: Correspondences between data values Many-to-many mappings Automatically inferring new entries Respect autonomy of the peers Supports value search (point queries) Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

18 Comparison of Approaches Hyperion: Semantics of Mapping Tables Mapping table: X Y with sets of attribute values resp. variables X, Y (many-to-many) Semantics of practical interest: closed-open-world, closed-closed-world Influences combination of mapping tables Open- Closedworld world present Any indicated X -value Y-value Y-values missing Any no X -value Y-value Y-value Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

19 Hyperion: Example Comparison of Approaches GDB id SwissProt id MIN id GDB: P GDB: O GDB: P GDB id GDB: SwissProt id O00662 GDB id MIM id GDB: Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

20 Comparison of Approaches Logical Relational Model [SGMB03] Domain relation: any subset of dom i dom j Relational space: set of local databases and a domain relation Coordination formula: CF ::= i : φ CF CF CF CF CF CF i : x.cf i : x.cf (i set of peers) Example: (Doc : fn, ln, pn, gender, pr). (Doc : Patient(1234, fn, ln, pn, gender, pr) Hospital : (hid, n, a).patient(hid, 1234, n, gender, a, Davis, pr) n = concat(fn, ln))) Query answering: coordination formulas as deductive rules Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

21 Comparison of Approaches Logical Relational Model Data model Relational Mapping language Coordination formulas: Subset of FOL (implication, conjunction, disjunction, universal and existential quantification wrt. different domains) Query language Equal to mapping language Peer autonomy Preserved (recursive local reasoning) Semantics of query answering Local reasoning (satisfyability of coordination formulas) Query optimization unknown Other Update propagation (using coordination formulas) Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

22 Comparison of Approaches Humboldt Peers [Rot07] Data model Mapping language Query language Peer autonomy Semantics of query answering Query optimization Other Relational extensionally sound GaV: x ȳ(φ S ( x, ȳ) z g( x, z)) extensionally sound LaV: x ȳ(s( x, ȳ) z φ G ( x, z)) CQ with semi-interval selections Highly preserved Exchange of certain answers Completeness-driven pruning, limitation of resource consumption Cardinality estimation based on query feedback Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

23 Comparison of Approaches Active XML [ABM08] Data model Mapping language Query language Peer autonomy Semantics of query answering Query optimization XML with web service invocations web services XQuery, XPath Limited Reasoning encapsulated by web services Several techniques considering embedded web service calls Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

24 Conclusion + Future Research Conclusion PDMS: flexible architecture for large-scale information sharing Main system characteristics: mapping and query languages, peer autonomy, semantics Semantics depend on interpretation of mappings Comparison of existing PDMS approaches Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

25 Conclusion + Future Research Future Research Reduce redundancy in query answering Considering data quality in query answering Building and optimizing of network of peers and mappings Dealing with different/varying data models and query languages Approximative query processing and non-standard query operators (e.g., top-k) Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

26 References I Conclusion + Future Research [ABM08] [AKK + 03] [ANR07] [BCHL05] [CGL + 04] S. Abiteboul, O. Benjelloun, and T. Milo. The Active XML project: an overview. VLDB J., 17(5): , M. Arenas, V. Kantere, A. Kementsietsidis, I. Kiringa, R. J. Miller, and J. Mylopoulos. The Hyperion project: From data integration to data coordination. ACM SIGMOD Record, 32(3):53 58, Alexander Albrecht, Felix Naumann, and Armin Roth. Networked PIM using PDMS. In Proc. of the Workshop on Networking Meets Databases (NetDB), A. Bonifati, Q. Chang, T. Ho, and L.V.S. Lakshmanan. HepToX: Heterogeneous peer to peer XML databases. Technical report, U. of British Columbia and Icar CNR, Italy, D. Calvanese, G. De Giacomo, M. Lenzerini, R. Rosati, and G. Vetere. Hyper: A framework for peer-to-peer data integration on grids. In Proc. of the Int. Conference on Semantics of a Networked World: Semantics for Grid Databases (ICSNW 2004), Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

27 References II Conclusion + Future Research [CGLR04] [HHNR05] [HIMT03] [HIST03] [HRZ + 08] Diego Calvanese, Giuseppe De Giacomo, Maurizio Lenzerini, and Riccardo Rosati. Logical foundations of peer-to-peer data integration. In Proc. of the Symposium on Principles of Database Systems (PODS), Ralf Heese, Sven Herschel, Felix Naumann, and Armin Roth. Self-extending peer data management. In Proc. of the Conf. Datenbanksysteme in Business, Technologie und Web (BTW), Karlsruhe, Germany, Alon Y. Halevy, Zachary Ives, Peter Mork, and Igor Tatarinov. Piazza: Data management infrastructure for semantic web applications. In Proc. of the Int. World Wide Web Conf. (WWW), Alon Y. Halevy, Zachary Ives, Dan Suciu, and Igor Tatarinov. Schema mediation in peer data management systems. In Proc. of the Int. Conf. on Data Engineering (ICDE), Katja Hose, Armin Roth, Andrï 1 Zeitz, Kai-Uwe Sattler, and Felix Naumann. 2 A research agenda for query processing in large-scale peer data management systems. Information Systems, 33(7-8): , Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28

28 References III Conclusion + Future Research [KAM03] A. Kementsietsidis, M. Arenas, and R. J. Miller. Mapping data in peer-to-peer systems: Semantics and algorithmic issues. In SIGMOD 2003, pages , [MBDH02] J. Madhavan, P. A. Bernstein, P. Domingos, and A. Y. Halevy. Representing and reasoning about mappings between domain models. In Proc. of the National Conf. on Artificial Intelligence (AAAI), [OV99] [Rot07] [SGMB03] M. T. Özsu and P. Valduriez. Principles of distributed database systems. Prentice Hall, 2nd edition, Armin Roth. Completeness-driven query answering in peer data management systems. In Proc. of the VLDB 2007 PhD Workshop, L. Serafini, F. Giunchiglia, J. Mylopoulos, and P. A. Bernstein. Local relational model: A logical formalization of database coordination. In Proc. of CONTEXT, Armin Roth (HPI, Potsdam, Germany) Peer Data Management Systems Nov. 10, / 28