Post on 11-May-2015
description
ϕArmin Haller | δTudor Groza | ξFlorian Rosenberg
Interacting with Linked Data via Semantically Annotated WidgetsJoint International Semantic Technology Conference
ϕCSIRO ICT Centre, Australia|W3C AustraliaδQueensland University, AustraliaξIBM T.J. Watson, NY, USA
A little motivation for the work…
… why interacting with the Linked data Web?
Linked data Web
Building a Web of Data …
… four principles
Publishing, interlinking data in RDF via de-referenceable URIs
Publishing RDF
Two (standardised) serialization formats to publish RDF (graphs)
1. RDF/XML
2. RDFa
RDF/XML
Widely used to publish linked data
All benefits of XML, but …
… syntax difficult for humans to read and write
… additional to HTML
… needs full control over publishing infrastructure (Rewrites etc.)
RDFa
Relatively new format, but used by already 5% of web sites
Interwoven within the HTML DOM …
… existing content within the page can be marked up with RDFa
… no additional control over publishing infrastructure needed
RDFa example
Simple page about a book<html>
<head>
<title>The Art of Computer Programming, Volume 1: Fundamental Algorithms</title>
</head>
<body>
<div><img src="theartofprogramming.jpg" /></div>
<div>Donald E. Knuth</div>
<div>Edition 3</div>
<div>Addison-Wesley Professional</div>
<div>672 pages</div>
<div>ISBN-10: 0201896834</div>
</body>
</html>
RDFa example
Simple page about a book<html>
<head prefix="dc: http://purl.org/dc/terms/“ base="http://example.org/book/TAoCP>
<title about="" property="dc:title">The Art of Computer Programming, Volume 1: Fundamental Algorithms</title>
</head>
<body>
<div about="">
<div><img src="theartofprogramming.jpg" /></div>
<div property="dc:creator">Donald E. Knuth</div>
<div>Edition 3</div>
<div property="dc:publisher">Addison-Wesley Professional</div>
<div property="dc:SizeOrDuration">672 pages</div>
<div property="dc:identifier">ISBN-10: 0201896834</div>
</div>
</body>
</html>
@prefix dc: <http://purl.org/dc/terms/> .@prefix : <http://example.org/book/> .
:TAoCP dc:title "Art of Computer Programming, Volume 1: Fundamental Algorithms" .
:TAoCP dc:creator "Donald E. Knuth" .
:TAoCP dc:publisher "Addison-Wesley Professional" .
:TAoCP dc:SizeOrDuration ”672 pages" .
:TAoCP dc:identifier "ISBN-10: 0201896834" .
Embedded triples
RDFa – provider vs. user content
RDFa only usable for provider created content
Ideally, all user input data should be part of the RDF graph, …
… currently no mechanism in RDFa to type user created content (within the DOM)
Example user created content in Web forms
e.g. Buy a TV online (e.g. Amazon, Ebay)First Name:
Last Name:
Jane
Doe
Email: jane.doe@example.com
Password: ********
Gender:
Birthday: 03 04 1976
Male Female
Example user created content in Web forms
e.g. Buy a TV online (e.g. Amazon, Ebay)
1976
First Name:
Last Name:
Jane
Doe
Email: jane.doe@example.com
Password: ********
Gender:
Birthday: 03 04
Male Female
1976
Female
Delivery Address:
10 Downing Street
London
SW1A 2AA
United Kingdom
Category:
Product Name:Description:
Price:
Amount
LCD Television
Sony Bravia LX9000
Your complete 3D experience from Sony
1500
1
USD
Example user created content in Web forms
e.g. Buy a TV online (e.g. Amazon, Ebay)
1976
First Name:
Last Name:
Jane
Doe
Email: jane.doe@example.com
Password: ********
Gender:
Birthday: 03 04
Male Female
1976
Female
Delivery Address:
10 Downing Street
London
SW1A 2AA
United Kingdom
Category:
Product Name:Description:
Price:
Amount
LCD Television
Sony Bravia LX9000
Your complete 3D experience from Sony
1500
1
USD
1 197604Cardholder:
CC Number:
Expiry Date:
CVV: 999
Price:
Type: Mastercard
Jane Doe
5999 9999 9999 9999
04 13
25 GBP
No annotation for user created content
Form input elements can be annotated with RDFa …
… but, RDFa annotations for input data are not possible ® no binding mechanism in RDFa
No annotation for user created content (cont’d)
Provider content vs. User created content
1976
Female
Delivery Address:
10 Downing Street
London
SW1A 2AA
United Kingdom
® Provider data | RDFa® Provider data | RDFa® Provider data | RDFa
® Provider data | RDFa® User data | Key/Value
pair® User data | Key/Value
pair® User data | Key/Value
pair® User data | Key/Value
pair® User data | Key/Value
pair
Category:
Product Name:Description:
Price:
Amount
LCD Television
Sony Bravia LX9000
Your complete 3D experience from Sony
1500
1
USD
No annotation for user created content (cont’d)
e.g. “Jane” can not be defined as foaf:firstName
First Name:
Last Name:
Jane
Doe
Email: jane.doe@example.com
Password: ********
Gender:
Birthday: 03 04 1976
Male Female
<div about="" property="foaf:firstName" content=""> <input type="text" name=“First Name" value="" />
</div>span>
No binding!
Publishing and Reusing user created content on the
Linked Data Web!
Model and System for semantic Web applications
– RDF-based model for forms (RaUL)http://purl.org/NET/raul#
– RESTful Web service (ActiveRaUL)http://w3c.org.au/raul
– Client-side JavaScript RDFa API
ActiveRaUL system architecture
Model:RaUL RDF model
Controller:Web service that maps HTTP terms to CRUD operations on RaUL widgets
View:Rendering service to serialise RaUL-based widgets in XHTML+RDFa
Usage Scenario
1. Form Modeling: Model widgets (forms) in RDF based on the RaUL ontology
2. Form Deployment: Submit form with HTTP POST to ActiveRaUL
3. Form Usage:Access/Use a form model with GET/POST to ActiveRaUL
Form Modeling
• RDFa User Interface Language(RaUL) Ontology for widget(form) control elements
• Data binding mechanism to reference external schemas for data (e.g. foaf:firstname, gr:category)
RaUL Form Model
Widget (form) meta model
RaUL Form Model – Triples defining the form structure
Category:
Product Name:
LCD Television
Sony Bravia LX9000
Description:
Price:
® raul:textbox
® raul:textbox
® raul:textbox
® raul:textbox/raul:listbox
® raul:textbox
Your complete 3D experience from Sony
1500
Amount 1
USD
RaUL Form Model – Triples defining the form input data
Category:
Product Name:
LCD Television
Sony Bravia LX9000
Description:
Price:
® gr:category
® rdfs:label
® rdfs:comment
® gr:currency/gr:hasUnitOfMeasurement
® gr:amountOfThisGood
Your complete 3D experience from Sony
1500
Amount 1
USD
Form Deployment• RESTful service for managing
Web widgets (forms)
• Maps HTTP verbs to SPARQLqueries on RaUL model
• Algorithm for generating widget models from arbitrary RDF graphs
• Example: Form uploadPOST /public/forms HTTP/1.1
Host: w3c.org.au/raul
Content-Type: application/xml
<rdf:…/>
Form Deployment• RESTful service for managing
Web widgets (forms)
• Maps HTTP verbs to SPARQLqueries on RaUL model
• Algorithm for generating widget models from arbitrary RDF graphs
• Example: Form upload
Created (201)
Location: http://w3c.org.au/raul/public/forms/add-product
Form Usage
1. Web user retrieves Web forms (and content) using ActiveRaUL (via browser)
2. ActiveRaUL returns web form in:• RDF/XML, RDF/JSON• HTML+RDFa view rendering
3. User fills out forms and submits data to ActiveRaul
HTML+RDFa view rendering<html><head> <base href="#addProduct"/> <meta property="raul:title" content="Add Product"/> <title>Add Product</title></head><body>
…
<div xmlns=http://www.w3.org/1999/xhtml
about="http://w3c.org.au/forms/productAdd1#product" typeof="raul:Textbox">
<span property="raul:label">Product URI:</span>
<span style="display:none;">
<span property="raul:id">product</span>
<span property="raul:name">product</span>
<span property="raul:value">http://w3c.org.au/forms/productAdd1#value_product</span>
</span>
</div>
…
<div xmlns="http://www.w3.org/1999/xhtml" about="http://w3c.org.au/forms/productAdd1#product_name"
typeof="raul:Textbox">
<span property="raul:label">Product Name:</span>
<span style="display:none;">
<span property="raul:id">product_name</span>
<span property="raul:name">product_name</span>
<span property="raul:value">http://w3c.org.au/forms/productAdd1#value_product_name</span>
</span>
</div>
<div style="display:none;" about="http://w3c.org.au/forms/productAdd1#value_product_name">
<span xmlns="http://www.w3.org/1999/xhtml"
property="rdf:subject">http://w3c.org.au/forms/productAdd1#defaultSubject</span>
<span xmlns="http://www.w3.org/1999/xhtml" property="rdf:predicate">gr:name</span>
<span xmlns="http://www.w3.org/1999/xhtml" property="rdf:object"></span>
</div>
Form Usage
Data Reuse• Link to existing, local data or data in
the Linked Data Web– Client-side JS RDFa API can retrieve data
directly from URI or via Sindice and prefills form controls
Category:
Product Name:Description:
Price:
Amount
USD
Product:
Form Usage
Data Reuse• Link to existing, local data or data in
the Linked Data Web– Client JS API retrieves data directly from URI
or via Sindice and prefills form controls
Category:
Product Name:Description:
Price:
Amount
USD
Product: http://bestbuy.com/…
Form Usage
Data Reuse• Link to existing, local data or data in
the Linked Data Web– Client JS API retrieves data directly from URI
or via Sindice and prefills form controls
Category:
Product Name:
LCD Television
Sony Bravia LX9000
Description:
Price:
Your complete 3D experience from Sony
Amount
USD
Product URI: http://bestbuy.com/…
Evaluation
Quantitative evaluation to analyse possible performance issues of our approach
Performance of the ActiveRaUL framework is influenced by two factors:
(i) overhead introduced by the RDFa annotations
(ii) performance of the widget/model generation
Evaluation - Overhead
• Comparison of request sizes for HTTP GET requests and HTTP PUT/POST requests and responses
Form Element
XHTML (in Byte)
XHTML + RDFa (Byte)
# of Triples Overhead in %
min max min max min max min max
Widget 72 115 251 376 3 6 248% 226%
Textbox 41 100 88 377 2 7 114% 277%
Listbox 49 125 228 459 5 9 365% 367%
Button 48 81 98 415 2 8 104% 412%
Evaluation - Overhead
• Comparison of request sizes for HTTP GET and HTTP PUT/POST requests and response
Form Element
XHTML (in Byte)
XHTML + RDFa (Byte)
# of Triples Overhead in %
min max min max min max min max
Widget 278 321 525 617 3 6 89% 92%
Textbox 239 298 454 613 2 7 90% 105%
Listbox 274 323 656 758 5 9 139% 135%
Button 245 278 459 720 2 8 87% 159%
Evaluation – Overhead – Discussion
• Content overhead a result of using RDFa for the annotation of the semantic forms/widgets
• We talk about adding one/two digit numbers of Kilobytes!– Acceptable in most cases– Common and accepted practice to add RDFa to HTML
Evaluation – Performance of view generationMeasured time required to generate an increasing number (1, 10 and 100) of widget elements
Results
• linear scalability for all widget elements
• Listbox and Listitems, also linear, but with a much higher factor (100x10)
In reality (for usability reasons) interesting ranges are between 10 and 30 widget elements
Conclusion
ActiveRaUL combines Web engineering with principles of Linked Open Data/Semantic Web
• RDFa annotated Web forms• well-defined publishing and usage lifecycle
Advantages:
(a) full machine understandable structured form data
(b) structured form data is encoded directly in the Web page and usable to any SW application
(c) typing of the form data via reference to standard ontologies
(d) automatic retrieval of form data from the Linked Data Web, and
(e) fully browser agnostic approach (rendering in XHTML + RDFa)