1 / 25

GridVine: Building Internet-Scale Semantic Overlay Networks

GridVine: Building Internet-Scale Semantic Overlay Networks. By Lan Tian. Outline. Introduction Overview of our Approach The P-Grid P2P system Semantic Support Semantic Interoperability Related Work Summary. Introduction. What is semantic Overlay Network?. ▫ ARTICLE artPK title

herb
Download Presentation

GridVine: Building Internet-Scale Semantic Overlay Networks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. GridVine: Building Internet-ScaleSemantic Overlay Networks By Lan Tian

  2. Outline • Introduction • Overview of our Approach • The P-Grid P2P system • Semantic Support • Semantic Interoperability • Related Work • Summary

  3. Introduction What is semantic Overlay Network?

  4. ▫ ARTICLE artPK title pages ▫ AUTHOR artFK name ▫ PUBLICATION pubID title date author Schema mapping SELECT artPK AS pubID UNION SELECT null AS pubID title AS title null AS title null AS date null AS date null AS author name AS author FROM ARTICLE FROM AUTHOR

  5. Introduction • Based on federated databases • Realization of semantic overlay networks in order to enable semantic interoperability • Key aspect: data independence - logical layer: supports semantic interoperability; provides semantic gossiping - physical layer: provides operations exploiting a structured overlay network,P-Grid

  6. Introduction • Requires mappings of operations and data to the physical layer - Introduction of a specific name space present in the peer space - The mapping of data and metadata to routable keys - The implementation of traversals of the semantic network for querying using intermediate schema mapping

  7. Outline • Introduction • Overview of our Approach • The P-Grid P2P system • Semantic Support • Semantic Interoperability • Related Work • Summary

  8. Data Independence • Two-layer model Insert(RDF schema) SearchFor(query) Return(tuples) Insert(RDF triple) Insert Schema translation) Logical Layer (GridVine) Insert(key, value) Retrieve(key) Return(value) Physical Layer (P-Grid)

  9. Data Independence • P-Grid is an efficient, self-organizing and fully decentralized access structure • GridVine uses two of P-Grid‘s basic functionlities: Insert(key, value) and Retrieve(key) • Choose RDF/RDFS as languages to encode metadata and vocabulary definitions in GridVine

  10. Decentralized Semantics • Schema inheritance - provides GridVine with basic schema reusability and interoperability • Semantic Gossiping - applied to foster semantic interoperability in decentralized settings - Query forwarding ▫ iterative forwarding ▫ recursive forwarding

  11. Outline • Introduction • Overview of our Approach • The P-Grid P2P system • Semantic Support • Semantic Interoperability • Related Work • Summary

  12. The P-Grid P2P system • GridVine uses P-Grid system as physical layer • P-Grid is based on the principles of distributed hash tables(DHT) • Peers refer to a binary tree structure • Each peer p ∈ P is associated with a leaf • Each leaf corresponds to a binary string Л∈∏ --> each peer associated with a path • Each peer stores a set of data items δ(p) • For d ∈δ(p) binary key key(d) has Л(p) as prefix

  13. Outline • Introduction • Overview of our Approach • The P-Grid P2P system • Semantic Support • Semantic Interoperability • Related Work • Summary

  14. Semantic Support • Metadata Storage - URI Schemes p-grid ://, for resource, p-grids://, for schema-elements - all resources identified by P-Grid URIs - Example : P-Grid resource 11110101(subject) is entitled(predicate) Rain, Stream and Speed(object) <?xml version="1.0"?> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <rdf:Description rdf:about="pgrid://11110101"> <Title xmlns="pgrids://01001101:bmp#">Rain, Steam and Speed</Title> </rdf:Description> </rdf:RDF>

  15. Metadata Storage • We reference each individual triple three times, generating seperate keys based on their subject, predicate and object values • Insertion operation of a triple t ∈T Insert(t) = Insert(tsubject, t), Insert(Hash(tpredicate),t), Insert(Hash(tobject), t)

  16. Schema Definition And Storage • Schematic information in GridVine is encoded using RDFS • P-Grid meta-schema and its relation to user-defined RDF schemas P-Grid Meta Schema P-Grid Data Item P-Grid Data Item Property Rdfs:domain Rdfs:subClassOf Rdfs:subPropertyOf Schema Schema concept Rdfs:domain

  17. Resolving Queries in GridVine • Simplest query with one bound variable SELECT ?y WHERE (<p-grid://01101000>, ?y, ?z) - return all the predicates used to annotate data item 01101000 • Implementation • Subject ,predicate and object can all be replaced by variables which may be bound or not

  18. Outline • Introduction • Overview of our Approach • The P-Grid P2P system • Semantic Support • Semantic Interoperability • Related Work • Summary

  19. Semantic Interoperability • Schema Inheritance P-Grid Meta Schema Rdfs:domain P-Grid Data Item P-Grid Data Item Property Rdfs:subPropertyOf Rdfs:subClassOf Rdfs:subPropertyOf Image File Rdfs:domain Title Width Rdfs:domain Rdfs:subPropertyOf Rdfs:subClassOf JPEG File JPEG IF Offset Rdfs:domain

  20. Semantic Gossiping • Aims at establishing global forms of agreement starting from a graph of purely local mappings among schemas • Semantic neighbourhood • Network can be seen as a directed graph of translations • Two interesting properties : - Transitivity allows for the forwarding of queries to semantic domains for which there is no direct translation link - Check the quality of translations

  21. Semantic Gossiping • Translation links are stored as OWL documents <?xml version="1.0"?> <?xml version="1.0" encoding="ISO-8859-1" ?> <rdf:RDF xmlns:owl ="http://www.w3.org/2002/07/owl#" xmlns:rdf ="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <Image_Description xmlns="pgrids://10000101:exif#"> <owl:equivalentProperty rdf:ID="m1" rdf:resource="pgrids://01001101:bmp#Title"/> </Image_Description> <Exif_Image_Width xmlns="pgrids://10000101:exif#"> <owl:equivalentProperty rdf:ID="m2" rdf:resource="pgrids://01001101:bmp#Width"/> </Exif_Image_Width> </rdf:RDF>

  22. Outline • Introduction • Overview of our Approach • The P-Grid P2P system • Semantic Support • Semantic Interoperability • Related Work • Summary

  23. Related Work • Hyperion: proposes an architecture and outlines a set of challenges for decentralized data management in P2P Systems • SWAP: Approach combining P2P and Semantic Web techniques • Edutella: employs a super-peer topology and facilitates the clustering of data based on ontology, rule, or query

  24. Related Work • PeerDB: - facilitates sharing of data without shared schema; - combines the power of mobile agents into P2P systems to perform operations at peers’ sites • Pizza peer data management project: - takes an approach to semantic heterogeneity that is similar to Semantic Gossiping; - provides no measures to judge correctness

  25. Summary • Introduction • Overview of our Approach - Data Independence - Decentralized Semantics • The P-Grid P2P system • Semantic Support - Metadata Storage - Schema Definition And Storage - Resolving Queries in GridVine • Semantic Interoperability - Schema Inheritance - Semantic Gossiping • Related Work

More Related