1. Chapter 04 Semantic Web Application Architecture 23 November 2015 A Team 오혜성, 조형헌, 권윤, 신동준, 이인용

2. 2/19  So far, we’ve learned… Introduction (1/2)

3. 3/19  RDF Application ‒ Software that does various things to make ‘Semantic Web’ available ‒ Need to know its structure to make models  Learn about ‒ RDF Parser/Serializer ‒ RDF Store ‒ RDF Query Engine ‒ Application Code Introduction (2/2)

4. 4/19  RDF Parser ‒ Program that read contents from.rdf files  RDF Serializer ‒ Program that does the opposite ‒ May translate in same or different text form RDF Parser/Serializer RDF Text RDF Triple Store RDF Text

5. 5/19  Round-Tripping ‒ Using Parser/Serializer each once to reverse their effect ‒ Reading from RDF Format text, convert to Triple Store, then re- converting, does not guarantee the same text file RDF Parser/Serializer RDF Text RDF Triple Store

6. 6/19  Converter ‒ Used for non-RDF data (e.g., tabular data) to convert it to RDF ‒ Can be done quite easily RDF Parser/Serializer -Other Data Sources SPO metro:item0rdf:typemetro:Metro Converter RDF Triple Store Tabular Data

7. 7/19  Microformats ‒ For authors willing to embed the structure data in web page ‒ Does not appear in browser ‒ Easier to extract data from web pages ‒ Ensures the intended meaning of document while converting  RDFa ‒ W3C Standard HTML tag ‒ Facebook adopted it as part of Open Graph Protocol RDF Parser/Serializer -Other Data Sources

8. 8/19  RDF Store ‒ System that store RDF data ‒ Simplest implementation of a triple store is ‘Singular table with 3 columns’ ‒ Contrast to RDB data store, RDF Store can ‘merge’ two data sets RDF Store Singular table form

9. 9/19  For all RDB data store ‒ All are Based on relation algebra ‒ But, hard to transfer whole database from one system to another  For all RDF Store ‒ Has the standard serialization language (e.g., RDF/XML ) ‒ Easy to transfer the data to another RDF Parser/Serializer -Data Standards and interoperability

10. 10/19  RDF query engine is intimately tied to the RDF store ‒ To solve a query, the engine relies on the indices and internal representations of the RDF store ‒ More finely tuned the store, the better its performance  SPARQL ‒ From the common features of query languages, W3C has undertaken the process of standardizing an RDF query language RDF Query Engines

11. 11/19  SPARQL endpoints ‒ SPARQL query engine provides another source of data for the semantic web ‒ SPARQL endpoint accepts queries and returns results via HTTP ‒ SPARQL endpoints provide access to large amounts of structured RDF data RDF Query Engines

12. 12/19  Comparison to relational queries  Oracle provides its own SPARQL extension ‒ Optimized for graph queries ‒ Making RDF queries accessible to SQL programmers ‒ Smoothly integrated with the table/join structure of SQL scripting language Comparison to relational queries Relational queriesRDF queries Based on the relational algebra of joins and foreign key references Look more like statements in predicate calculus Unification variables are used to express constraints between the patterns Describes a new data table that is formed by combining two or more source tables Describe a new graph that is formed by describing a subset of a source RDF graph

13. 13/19  Database applications include some application code besides database and query engine  RDF application includes RDF parser and serializer, converters, RDF merge functionality, and RDF query engine Application code Application RDF Files Analytics Interface … Converters and Scrapers Parser and Serializer RDF Store (merge) Query Engine Application Analytics Interface … Database Query Engine Web pages, Spreadsheets, Tables, databases, etc..

14. 14/19  The RDF data model was designed from the beginning with data federation ‒ Information from any source is converted into a set of triples ‒ Data federation of any kind is accomplished with a single mechanism  Converts information from multiple sources into a single format  Combines all the information into a single store ‒ Federating information first and then querying the federated information store  Separates concern of data federation from operational concern of application  Queries written in application need not know where a particular triple came from Data federation database tables XML Web pages Spread sheets Triples Converters & Scrapers RDF Store (merge) Query Engine Subject Predicate Object Application