Download RDF Parser/Serializer

Chapter 04
Semantic Web
Application Architecture
23 November 2015
A Team
오혜성, 조형헌, 권윤, 신동준, 이인용
Introduction (1/2)
 So far, we’ve learned…
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Introduction (2/2)
 RDF Application
‒ Software that does various things to make ‘Semantic Web’ available
‒ Need to know its structure to make models
 Learn about
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RDF Parser/Serializer
RDF Store
RDF Query Engine
Application Code
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RDF Parser/Serializer
 RDF Parser
‒ Program that read contents from .rdf files
RDF Triple Store
RDF Text
 RDF Serializer
‒ Program that does the opposite
‒ May translate in same or different text form
RDF Triple Store
RDF Text
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RDF Parser/Serializer
 Round-Tripping
‒ Using Parser/Serializer each once to reverse their effect
‒ Reading from RDF Format text, convert to Triple Store, then reconverting, does not guarantee the same text file
RDF Triple Store
RDF Text
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RDF Parser/Serializer
-Other Data Sources
 Converter
‒ Used for non-RDF data (e.g., tabular data) to convert it to RDF
‒ Can be done quite easily
Tabular Data
S
P
O
metro:item0
rdf:type
metro:Metro
Converter
RDF Triple Store
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RDF Parser/Serializer
-Other Data Sources
 Microformats
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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
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RDF Store
 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
Singular table form
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RDF Parser/Serializer
-Data Standards and interoperability
 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
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RDF Query Engines
 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
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RDF Query Engines
 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
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Comparison to relational queries
 Comparison to relational queries
Relational queries
RDF queries
Based on the relational algebra of Look more like statements in predicate
joins and foreign key references
calculus
Unification variables are used to express
constraints between the patterns
Describes a new data table that is Describe a new graph that is formed by
formed by combining two or
describing a subset of a source RDF graph
more source tables
 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
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Application code
 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
Analytics
Interface
…
Application
Query Engine
Query Engine
Database
Analytics
Interface
…
Converters
and Scrapers
RDF Store
(merge)
Parser and
Serializer
RDF Files
Web pages, Spreadsheets,
Tables, databases, etc..
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Data federation
 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
database
tables
XML
Web
pages
Spread
sheets
Converters &
Scrapers
RDF Store
(merge)
Triples
Subject
Predicate
Object
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Query
Engine
Application