Apache Marmotta - Introduction
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Apache Marmotta is a linked data platform that provides a linked data server, SPARQL server, and development environment for building linked data applications. It uses modular components including a triplestore backend, SPARQL endpoint, LDCache for remote data access, and an optional reasoner. Marmotta is implemented as a Java web application and uses services, dependency injection, and REST APIs.
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Apache Marmotta - Introduction
- 1. Apache Marmotta: Introduction Sebastian Schaffert
- 2. Who Am I Dr. Sebastian Schaffert Senior Researcher at Salzburg Research Chief Technology Officer at Redlink GmbH Committer at Apache Software Foundation … and starting 12/2014 Software Engineering Manager (SRE) @ Google [email protected] http://linkedin.com/in/sebastianschaffert http://www.schaffert.eu
- 3. Agenda ● Introduction to Apache Marmotta (Sebastian) – Overview – Installation – Development ● Linked Data Platform (Sergio & Jakob) – Overview – Practical Usage ● Semantic Media Management (Thomas) – Media Use Case – SPARQL-MM
- 4. Overview
- 5. What is Apache Marmotta? ● Linked Data Server (implements Content Negotiation and LDP) ● SPARQL Server (public SPARQL 1.1 query and update endpoint) ● Linked Data Development Environment (collection of modules and libraries for building custom Linked Data applications) ● Community of Open Source Linked Data Developers … all under business friendly Apache Open Source licence
- 6. Linked Data Server ● easily offer your data as Linked Data on the Web ● human-readable and machine-readable read-write data access based on HTTP content negotiation ● reference implementation of the Linked Data Platform (see next presentation block)
- 7. SPARQL Server ● full support of SPARQL 1.1 through HTTP web services ● SPARQL 1.1 query and update endpoints ● implements the SPARQL 1.1 protocol ( supports any standard SPARQL clients) ● fast native implementation of SPARQL in KiWi triple store ● lightweight Squebi SPARQL explorer UI
- 8. Linked Data Development ● modular server architecture allows combining exactly those functionalities needed for a use case (no need for reasoning? exclude reasoner ...) ● collection of independent libraries for common Linked Data problems – access Linked Data resources (and even some that are not Linked Data) – simplified Linked Data query language (LDPath) – use only the triple store without the server
- 9. Community of Developers ● discuss with people interested in getting-things- done in the Linked Data world ● build applications that are useful without reimplementing the whole stack ● thorough software engineering process under the roof of the Apache Software Foundation
- 10. Installation / Setup (we help you) https://github.com/wikier/apache-marmotta-tutorial-iswc2014
- 11. Sample Project ● Requirements: – JDK 7/8 (https://java.com/de/download/) – Maven 3.x (http://maven.apache.org) – git (http://git-scm.com/) – curl (http://curl.haxx.se/) https://github.com/wikier/apache-marmotta-tutorial-iswc2014
- 12. Sample Project $ git clone [email protected]:wikier/apache-marmotta-tutorial-iswc2014.git $ cd apache-marmotta-tutorial-iswc2014 $ mvn clean tomcat7:run … then point browser to http://localhost:8080 https://github.com/wikier/apache-marmotta-tutorial-iswc2014
- 14. Apache Marmotta Platform ● implemented as Java web application (deployed as marmotta.war file) ● service oriented architecture using CDI (Java EE 6) ● REST web services using JAX-RS (RestEasy) ● CDI services found on classpath are automatically added to system
- 15. Architecture
- 16. Marmotta Core (required) ● core platform functionalities: – Linked Data access – RDF import and export – Admin UI ● platform glue code: – service and dependency injection – triple store – system configuration – logging
- 17. Marmotta Backends (one required) ● choice of different triple store backends ● KiWi (Marmotta Default) – based on relational database (PostgreSQL, MySQL, H2) – highly scalable ● Sesame Native – based on Sesame Native RDF backend ● BigData – based on BigData clustered triple store ● Titan – based on Titan graph database (backed by HBase, Cassandra, or BerkeleyDB)
- 18. Marmotta SPARQL (optional) ● SPARQL HTTP endpoint – supports SPARQL 1.1 protocol – query: …/sparql/select – update: …/sparql/update ● SPARQL explorer UI (Squebi)
- 19. Marmotta LDCache (optional) ● transparently access Linked Data resources from other servers as if they were local ● support for wrapping some legacy data sources (e.g. Facebook Graph) ● local triple cache, honors HTTP expiry and cache headers Note: SPARQL does NOT work well with LDCache, use LDPath instead!
- 20. Marmotta LDPath (optional) ● query language specifically designed for querying the Linked Data Cloud ● regular path based navigation starting at a resource and then following links ● limited expressivity (compared to SPARQL) but full Linked Data support @prefix local: <http://localhost:8080/resource/> ; @prefix foaf: <http://xmlns.com/foaf/0.1/>; @prefix mao: <http://www.w3.org/ns/ma-ont#>; likes = local:likes / (foaf:primaryTopic / mao:title | foaf:name) :: xsd:string;
- 21. Marmotta Reasoner (optional) ● implementation of rule-based sKWRL reasoner ● Datalog-style rules over RDF triples, evaluated in forward-chaining procedure @prefix skos: <http://www.w3.org/2004/02/skos/core#> ($1 skos:broaderTransitive $2) -> ($1 skos:broader $2) ($1 skos:narrowerTransitive $2) -> ($1 skos:narrower $2) ($1 skos:broaderTransitive $2), ($2 skos:broaderTransitive $3) -> ($1 skos:broaderTransitive $3) ($1 skos:narrowerTransitive $2), ($2 skos:narrowerTransitive $3) -> ($1 skos:narrowerTransitive $3) ($1 skos:broader $2) -> ($2 skos:narrower $1) ($1 skos:narrower $2) -> ($2 skos:broader $1) ($1 skos:broader $2) -> ($1 skos:related $2) ($1 skos:narrower $2) -> ($1 skos:related $2) ($1 skos:related $2) -> ($2 skos:related $1)
- 22. Marmotta Versioning (optional) ● transaction-based versioning of all changes to the triple store ● implementation of Memento protocol for exploring changes over time ● snapshot/wayback functionality (i.e. possibility to query the state of the triple store at a given time in history)
- 23. Apache Marmotta Walkthrough (Demo)
- 25. Apache Marmotta Libraries ● provide implementations for common Linked Data problems (e.g. accessing resources) ● standalone lightweight Java libraries that can be used outside the Marmotta platform
- 26. LDClient ● library for accessing and retrieving Linked Data resources ● includes all the standard code written again and again (HTTP retrieval, content negotiation, ...) ● extensible (Java ServiceLoader) with custom wrappers for legacy data sources (included are RDF, RDFa, Facebook, Youtube, Freebase, Wikipedia, as well as base classes for mapping other formats like XML and JSON)
- 27. LDCache ● library providing local caching functionality for (remote) Linked Data resources ● builds on top of LDClient, so offers the same extensibility ● Sesame Sail with transparent Linked Data access (i.e. Sesame API for Linked Data Cloud)
- 28. LDPath ● library offering a standalone implementation of the LDPath query language ● large function library for various scenarios (e.g. string, math, ...) ● can be used with LDCache and LDClient ● can be integrated in your own applications ● supports different backends (Sesame, Jena, Clerezza)
- 29. Marmotta Loader ● command line infrastructure for bulk-loading RDF data in various formats to different triple stores ● supports most RDF serializations, directory imports, split-file imports, compressed files (.gz, .bzip2, .xy), archives (tar, zip) ● provides progress indicator, statistics
- 30. KiWi Triplestore
- 31. KiWi Triplestore ● Sesame SAIL: can be plugged into any Sesame application ● based on relational database (supported: PostgreSQL, MySQL, H2) ● integrates easily in existing enterprise infrastructure (database server, backups, clustering, …) ● reliable transaction management (at the cost of performance) ● supports very large datasets (e.g. Freebase with more than 2 billion triples)
- 32. KiWi Triplestore: SPARQL ● translation of SPARQL queries into native SQL ● generally very good performance for typical queries, even on big datasets ● query performance can be optimized by proper index and memory configuration in the database ● almost complete support for SPARQL 1.1 (except some constructs exceeding the expressivity of SQL and some “bugs”)
- 33. KiWi Triplestore: Reasoner ● rule-based sKWRL reasoner (see demo before) ● fast forward chaining implementation of rule evaluation ● truth maintenance for easy deletes/updates ● future: might be implemented as stored procedures in database
- 34. KiWi Triplestore: Clustering ● cluster-wide caching and synchronization based on Hazelcast or Infinispan ● useful for load balancing of several instances of the same application (e.g. Marmotta Platform)
- 35. KiWi Triplestore: Versioning ● transaction-based versioning of triple updates ● undo transactions (applied in reverse order) ● get a Sesame repository connection visiting any time of the triple store history
- 36. Thank You! Sebastian Schaffert [email protected] supported by the European Commission FP7 project MICO (grant no. 610480)