RESTful writable APIs for the web of Linked Data using relational storage solutions
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This document discusses providing RESTful APIs for linked data using relational database storage. It describes translating SPARQL queries to SQL using the R2RML mapping language and exposing RDF graphs through a RESTful interface based on SPARQL HTTP protocol. Key points include mapping RDF quads to relational tables, generating SQL from SPARQL queries, and defining a RESTful API with URI templates mapped to SPARQL endpoints to manipulate named graphs in RDF format. The goal is to help make linked data technologies useful for building web APIs and expose more structured data on the web.
![RESTful API
• Minting of resource URIs
HTTP POST Request HTTP GET Response
graph_uri
[
<p1> <o1> ;
<uri> graph_uri#self
<p1> <o1> ;
<p2> <o2>;
<p2> <o2>;
...
...
]
RDF RDF
200
201
New resource URI](https://image.slidesharecdn.com/ldow2011-110329015032-phpapp01/85/RESTful-writable-APIs-for-the-web-of-Linked-Data-using-relational-storage-solutions-15-320.jpg)
RESTful writable APIs for the web of Linked Data using relational storage solutions
- 1. RESTful writable APIs for the web of Linked Data using relational storage solutions Antonio Garrote María N.Moreno García
- 2. Outline 1. Introduction 2. SPARQL to SQL mapping using R2RML 3. RESTful API 4. Conclusions
- 3. Web APIs OAuth Key Value Mobile App. Store HTTP API JS. App JSON MVC Native App. Dynamic Relational Web App. DB
- 4. Linked data APIs? • RDF data model vs JSON objects • Object IDs vs URIs • Properties identified by URIs vs plain strings • URIs linking data in different services
- 5. Transition path • Translation of SPARQL update queries into SQL queries • RDF graphs encoded in JSON objects • RESTful protocol to manipulate RDF graphs
- 6. SPARQL to SQL translation • R2RML starting point Relational RDF quads TableMappings Data R2RML Document
- 7. SPARQL to SQL translation • inverse transformation R2RML Document SPARQL Query QuadPatterns QuadMatchers SQL
- 8. SPARQL to SQL translation Constant Mappings R2RML Mapping (Table, Subject, Property, Object, Graph) Variable Mappings Quad Matchers
- 9. SPARQL to SQL translation (Table, Subject, Property, Object, Graph) Constant Terms Compatible? SPARQL Quad Pattern Variables +BNode IDs
- 10. SPARQL to SQL translation SELECT SPARQL Quad Pattern Quad Quad Quad Matcher Matcher Matcher σπ σπ σπ ∪ ∪ SPARQL Relational Algebra
- 11. SPARQL to SQL translation Insert SPARQL Quad Pattern Quad Quad Quad Matcher Matcher Matcher Min. Insertion Cost metric Insert / Update SQL DM Query
- 12. SPARQL to SQL translation • Different compatibility functions: data types, language tags in literals • R2RML extensions to generate IDs from URIs • Limitations: auto increment columns and database constraints
- 13. RESTful API • Starting point: “SPARQL 1.1 Uniform HTTP Protocol for Managing RDF graphs” • Granularity: RDF named graph • HTTP uniform interface semantics
- 14. RESTful API • Declarative definition of APIs (RDFS vocabulary) - URI templates - Mapping of templates to SPARQL endpoints
- 15. RESTful API • Minting of resource URIs HTTP POST Request HTTP GET Response graph_uri [ <p1> <o1> ; <uri> graph_uri#self <p1> <o1> ; <p2> <o2>; <p2> <o2>; ... ... ] RDF RDF 200 201 New resource URI
- 16. RESTful API • Extensions (linked-data-api): - JSON-LD as the primary media type - Method overloading - JSONP support - Format URL parameter - Pagination parameters
- 17. Sample Application • Library • Prototype - JavaScript client - RESTful API - FOAF+SSL auth - Relational backend http://github.com/antoniogarrote/clj-r2rml http://antoniogarrote.com/cvbuilder
- 18. Conclusions • Linked data and sem. web technologies can help us to build better web APIs • Huge opportunity to increase the amount of linked data available in the web • Real benefits for end users • Easy transition path for web developers must be provided