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Introduction

Data Ring: Let us turn the net into a database! Serge Abiteboul , INRIA-Futurs Neoklis Polyzotis, UC Santa-Cruz. Introduction. Success stories after the Internet bubble. Google: management of Web pages Mapquest: management of maps Amazone: book catalogue eBay: product catalogue

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Introduction

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  1. Data Ring: Let us turn the net into a database!Serge Abiteboul, INRIA-Futurs Neoklis Polyzotis, UC Santa-Cruz ADBIS06, Data ring

  2. Introduction

  3. Success stories after the Internet bubble • Google: management of Web pages • Mapquest: management of maps • Amazone: book catalogue • eBay: product catalogue • Napster (emule, bearshare, etc.): music database • Flickr: picture database • Wikipedia: dictionary They are all about publishing some database ADBIS06, Data ring

  4. A trend is towards peer-to-peer • P2P: • A large and varying number of computers cooperate to solve some particular task without any centralized authority • Goal: build an efficient, robust, scalable system based (typically) on inexpensive, unreliable computers distributed in a wide area network • Examples • seti@home: search for extraterrestrial intelligence • kazaa: obtain free music/video over the net • cabal: decryption of 512 bits RSA code • grub: P2P Web search ADBIS06, Data ring

  5. A trend is towards peer-to-peer • The Web is switching from centralized servers to communities and syndication • Buzzwords such as Web 2.0, infoware, annotations, interactivity • Some motivations • Social, organizational: no need to have a leader, more flexible • Technical: performance, availability, no bottleneck • Analogy: • Software development by very structured and controlled groups of programmers, e.g., Windows • Open-source software produced by large communities of autonomous developers, e.g., Linux ADBIS06, Data ring

  6. Data ring • Information management in a P2P network • Information is heterogeneous, distributed, replicated and dynamic • Data + knowledge + services • Peers are heterogeneous, autonomous and possibly mobile • Heterogeneous storage, bandwidth, computing power • From sensors to PDA to mainframe • Variety of requirements in terms of number of peers, QoS, performance, security, etc. • We will see motivations and examples ADBIS06, Data ring

  7. Acknowledgement – people & projects • Xyleme: Sophie Cluet, Guy Ferran & many others • Scalable XML repository • A start-up in 2000 • ActiveXML within EC DbGlobe project: Omar Benjelloun, Ioana Manolescu, Tova Milo & many others • Framework for 2P data management • KadoP within EC Edos project: Ioana Manolescu, Nicoleta Preda & many others • P2P scalable XML repository ADBIS06, Data ring

  8. Outline • Introduction • Data ring • XML query processing • P2P XML query processing • Logic and algebra for distributed data management • Automatic and distributed management • Other issues in brief • Conclusion ADBIS06, Data ring

  9. Data ring

  10. Functionalities:DBMS, content management and more • Storage, persistence, replication • Indexing, caching, query, update, optimization • Schema management, access control • Fault tolerance, self tuning, monitoring • Semantic enrichment, information retrieval, uncertain data, result ranking, multi-lingual… • Resource discovery, history, provenance • Each functionality may be achieved by a peer or by the network • This may depend on the nature of the application ADBIS06, Data ring

  11. The information in a data ring • Data: tuples, collections, documents, relations, objects… • Services: data sources, possibly some computation (e.g. genome) • Knowledge • Meta-data about resources: attribute/values pairs, annotations • Ontologies to explain data and metadata • Mapping between ontologies (for data integration) • Views (possibly recursive) • Physical data • Indices • Materialized views • Statistics for query optimization ADBIS06, Data ring

  12. A mainframe database A file system Web server A PC A PDA A telephone A sensor A home appliance A car A manufacturing tool A telecom equipment A toy Another data ring And now, what is a peer? ? Any connected device or software with information to share + a net address + names for its resources d@p, s@p’ ADBIS06, Data ring

  13. Example: Edos distribution system • A system for the management of Linux distribution • Joint work with Mandriva Software and U. Tel Aviv • Community of open-source developers: thousands • System releases: about 10 000 software packages + meta data • Package name, author; date, signature, documentation • Collections of packages, dependencies between packages • Functionalities • Query the metadata (also query subscription) • Retrieve packages • Update an existing release • Publish a new release (based on BitTorrent) ADBIS06, Data ring

  14. Main parameters of such applications • Number of peers • Number of documents • How volatile the peers are • The query workload • The update workload • The “network distance” between the peers • Edos: peers and documents in thousands, mostly append for updates, peers not too volatile • An extreme: Google search engine in P2P for billions of documents using millions of volatile peers ADBIS06, Data ring

  15. Lots of related work and related systems • Structured P2P nets: Pastry, Chord • Content delivery net: Coral, Akamai • XML repositories: Xyleme, DBMonet • Multicast systems: Avalanche, Bullet • File sharing systems: BitTorrent, Kazaa • Pub/Sub systems: Scribe, Hyper • Distributed storage systems: OceanStore, GoogleFS • Data spaces: Franklin, Halevy ADBIS06, Data ring

  16. Standards: The golden triangle of distributed content management on the Web • Standard for data exchange • XML, XML Schema… • Extensible Markup Language • Labeled ordered trees • Foundations: tree automata • Query languages • XPATH, XQuery… • Standards for distributed computing: Web services • SOAP, WSDL, UDDI, BPEL… • Simple Object Access Protocols • Corba but simpler and on the Web XML SOAP WSDL Xquery Xpath ADBIS06, Data ring

  17. Information used to live in islands but it is changing • Different formats: relational, metadata, documents, text, DXF • A Web standard for data exchange, XML, is fixing it • XML captures all kinds of information over a wide spectrum • XML comes with a family of emerging standards: XML schema, XSL/T, Xquery, domain specific schemas… • Different computers, platforms, languages, applications • A standard for Web services, SOAP, is fixing it • SOAP allows ubiquitous computing on the Internet • SOAP comes with a family of emerging standards: WSDL, UDDI • This provides a uniform access to information… • …the dream for distributed data management ADBIS06, Data ring

  18. Why XML? Because of its information spectrum Minimal structure Structured Data Hierarchy + Meta data Books Contracts Catalogs Bank accounts Emails Financial Reports Insurance Policies Economical Analysis Derivatives Inventory Political analysis Insurance Claims Financial News Sports News Resumes ADBIS06, Data ring

  19. A standard for information: XML • Labeled ordered trees where leaves are text • Marriage of document and database worlds • Marriage of full text indexing and structure indexing • Is it the ultimate data model? No • Purely syntax – more semantics needed • Is it OK for now? Definitely yes (because it is a standard) ADBIS06, Data ring

  20. The main asset of XML (vs. HTML) = typing product-table product reference price designation description • Applications need typing • XML typing: DTD and XML schema • Trees • Semantics and structure are in tags and paths • product-table/product/reference • product-table/product/price ADBIS06, Data ring

  21. A standard for distributed computing: Web services • Possibility to activate a method on some remote Web server • Exchange information in XML: input and result are in XML • Ubiquitous XML distributed computing infrastructure • 2 main applications • E-commerce • Access to remote data • With XML and Web services, it is possible • To get information from virtually anywhere • To provide information to virtually anywhere ADBIS06, Data ring

  22. A standard for XML queries: Xquery (soon a recommendation of W3C) • A “logic” for labeled tree – a declarative language • Inspired by SQL: standard for relation data • Inspired by OQL: standard for object databases • Functional as OQL • Not as clean as OQL • Mixes structure and content • Give me the documents where the word XML appears in title • Some full-text extension is coming • Also an update language and full-text capabilities ADBIS06, Data ring

  23. XML and Xquery • XML focuses on lists • Represent a very set of objects as a list • In our context, overhead in terms of index maintenance and query processing • Here we are mostly concerned with a “set-oriented” view of XML • Xquery is very complicated and powerful • OK for large documents on a server • Not appropriate for huge volumes of small documents on the Web • Here we are mostly concerned with tree pattern queries (a subset of XQuery) and full-text search ADBIS06, Data ring

  24. So to be honest • We take only what we want in the standard • Ignore order • Ignore complex features of XQuery • And even that is not what we need… ADBIS06, Data ring

  25. Thesis • This is fine for efficient query processing of local XML • This is not sufficient for distributed data management and flexible information integration • What made the success of the relational model, i.e., of tables on a server : • A logic for defining tables • An algebra for describing query plans over tables • By analogy, we need for trees in a P2P system • A logic for defining distributed data and data services • An algebra for describing query plans over these • Proposal: ActiveXML and query optimization around it ADBIS06, Data ring

  26. What we do next? • XML processing on a server • XML processing in a P2P system • ActiveXML • Then other data ring functions ADBIS06, Data ring

  27. T XML query processing

  28. Xyleme – in short • 1999: Xyleme research project at INRIA • 2000: Creation of a spin-off • 2006: About 25 people • Technology: a content warehouse built around a very efficient and scalable XML repository • Example: all articles of Le Monde in XML, financial reports in JP-Morgan ADBIS06, Data ring

  29. Xyleme Functionalities View and Semantic stemming, integration, classification… Exploiting GUI, Web services, reporting… Query Processing Store & Index Feeding Web ADBIS06, Data ring

  30. Xyleme Architecture Loader| Local | Query Loader| Local | Query Loader| Local | Query XML store XML store XML store Index Index Index Client side Applications IE/Java/C++/.Net Or Any Platform HTTP | Web Service API Server side or Application Server Tomcat|Soap Name Server User Manager Url Manager Notification Mgr Global Query Manager Java/C++ API Global Query Manager Corba ... ADBIS06, Data ring

  31. Structural identifiersand indexing hash(C) LAN Put(C;[d,p,6,6,1]) hash(“John) Put(“John”;[d,p,3,1,2]) 1 A 7 0 6 2 B C 4 6 1 1 X ancestor of Y <=> pre(X) < pre(Y) and post(X) > post(Y) 3 4 7 D E 1 F 3 5 2 2 2 5 G “John” X parent of Y <=> X ancestor of Y and level(X) = level(Y) - 1 2 3 Structural IDs = Prefix-Postfix-Level ADBIS06, Data ring

  32. Query evaluation based on Holistic twig joins (d1, 201, 400) A C D (d1, 224, 201) (d1, 228, 237) “John” (d1, 228, 237) ADBIS06, Data ring

  33. P2P XML processing

  34. Moving this to a P2P network – KadoP • Advantages: scaling Disadvantages: complexity • Performance • Optimization of parallelism • Avoid bottleneck • Replication • Availability • Replication • Cost • Avoid the cost of server • Share operational cost • Dynamicity • add/remove new data sources • Performance • Cost for complex queries • Communication cost • Availability • Peers can leave • Consistency maintenance • Difficult to support transaction • Quality • Difficult to guarantee quality ADBIS06, Data ring

  35. Typically on a WAN Peers come and go Standard interface Locate(k):: log(n) messages to fing the peer in charge of key k Put(k,v) Get(k): retrieves all the values for k We tried Pastry, Chord and JXTA We now use Pastry Not satisfactory for the system we want to develop example: locate, put Distributed hash tables hash(k) DHT put(k;v3) v1,v2,v3 put(k;v1) put(k;v2) get(k) ADBIS06, Data ring

  36. Use structured ID as in Xyleme Publish them in a DHT Use Holistic twig join Main issue: communications WAN vs. LAN Long posting lists Optimization techniques Use only docID [wisconsin] Ship smallest list Semi-join techniques Intensional indexing Indexing in KadoP hash(C) DHT hash(“John) put(C;[d,p,6,6,1]) put(“John”;[d,p,3,1,2]) hash(C) DHT ADBIS06, Data ring

  37. Such P2P systems scale… sort of… • If we consider • The Internet • Millions of peers • A “large” number of documents per peers • A “reasonable” query load per peer • This is placing too much load on the network • Lots of queries will result in intersecting posting lists on peers that are remote, e.g. US and Europe • Besides parallelism, we should use replication intensively • To intersect two long posting lists, I should be most likely to find two replicas that are nearby eachother • Very interesting distributed data management problem ADBIS06, Data ring

  38. Logic and algebra for distributed data management: ActiveXML

  39. ActiveXML • Recall the standards of distributed data management: XML, Web services, XQuery • ActiveXML = XML documents with embedded Web service calls where service calls are typically in Xquery • Web service provides: • Intensional data: not explicitly here • Dynamic: a new call may provide new data XML Xquery Xpath SOAP WSDL ADBIS06, Data ring

  40. ActiveXML = XML + embedded service calls(omitting syntactic details) <resorts state=‘Colorado’> <resort> <name> Aspen </name> <scond> Unisys.com/snow(“Aspen”) </scond> <hotels ID=AspHotels > …. Yahoo.com/GetHotels(<city name=“Aspen”/>) </hotels> </resort> … </resorts> <depth unit=“meter”>1</depth> May contain calls to any SOAP web service to any ActiveXML web services ADBIS06, Data ring

  41. Not a new idea in databasesNot a new idea on the Web • Mixing calls to data is an old idea • Procedural attributes in relational systems • Basis of Object Databases • In HTML world • Sun’s JSP, PHP+MySQL • Call to Web services inside documents • Macromedia MX, Apache Jelly ADBIS06, Data ring

  42. What exactly to exchange • A parameter of a call contains some service calls • The result of a call contains some service calls • Do we evaluate these calls before transmitting the data or not • Hi Pierre, what is the phone number of Number 10 in the French soccer team? • Find his name in wc2006.com/France/team.xml then look in fifa.PhoneBook.org • Look for Zidane in fifa.PhoneBook.org • 33 4 13 00 00 01 ADBIS06, Data ring

  43. When to activate the call • Explicit pull mode • Frequency: Daily, weekly, etc. • After some event: e.g., when another service call completed • This aspect of the problem is related to active databases • Implicit pull mode : Lazy • When the data is requested • Difficulty : detect that the result of a particular request may be affected by a particular call • This is related to deductive databases • Push mode • E.g., based on a query subscription; the web server pushes information to the client • E.g., synchronization with an external source • This is related to stream and subscription queries ADBIS06, Data ring

  44. Peer-to-peer architecture Each ActiveXML peer Repository: manages ActiveXML data with embedded web service calls Web client: uses Web services Web server: provides (parameterized) queries/updates over the repository as web services Open source system SUN’s Java SDK 1.4 XML parser XPath processor, XSLT engine Apache Tomcat 4.0 servlet engine Apache Axis SOAP toolkit 1.0 X-OQL query processor persistent DOM repository JSP-based user interface JSTL 1.0 standard tag library see http://activexml.net ActiveXML peer ActiveXML peer soap ADBIS06, Data ring

  45. ActiveXML is a logic for distributed tree management… and also an algebra • ActiveXML extended • Generic services: s@any • Send and receive (work on multicasting) • Stream and EoS • ActiveXML is restricted: recall we ignore node ordering • Novelties • Stream of trees vs. set of relations for the relational model • Distribution: exchange of query plans • Optimization & evaluation are interleaved ADBIS06, Data ring

  46. A simple example //paper[//author contains “Ullman”][//title contains “magic set”] Q@any Q@any Q@any paper author title Ring indexQ@local * d21@p2 d12@p6 “magic set” “Ullman” Query plan: evaluate: q locally or ship it to p2,p6 ADBIS06, Data ring

  47. A simple example - continued  get get • Optimization of the Index computation (indexQ)   send send     get get get get get Author get Title send send send send send send Author Title “magic set” “Ullman” “magic set” “Ullman” ADBIS06, Data ring

  48. Distributed query optimization • This provides an algebra for distributed query processing • Allows interleaving query processing and query optimization • Can interact with local optimizers • Based on XML flow and local XML flow processing • Most techniques that I know of can be captured • Horizontal decomposition, semi-join, replication, magic set… • Main issue to guide optimization is the gathering of statistics ADBIS06, Data ring

  49. Automatic and distributed management of the data ring

  50. Context • No centralized server • No information administrator (no info manager) • Most users are non-experts • E.g., scientists • Requirements • Ease of deployment (zero-effort) • Ease of administration (zero-effort) • Ease of publication (epsilon-effort) • Ease of exploitation (epsilon-effort) • Participation in community building notably via annotations ADBIS06, Data ring

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