A Semantic Data Model for Web Applications

Armin Haller & Florian Rosenberg
A Semantic Data Model for Web
Applications
CSIRO ICT Centre Conference

Semantic Web
Adds machine readable data to Web
resources

Semantic Web
“First step is putting data on the Web
in a form that machines can naturally
understand, or converting it to that
form. This creates what I call a
Semantic Web - a web of data that
can be processed directly or indirectly
by machines.” – Tim Berners-Lee

Web Resource
A page about a book
<html>
<head>
<title>Tractatus Logico-Philosophicus</title>
</head>
<body>

<img src="tractatus.png" /> 
Written by: Ludwig Wittgenstein 
With an Introduction by: Bertrand Russell


New York 
Harcourt, Brace & Company, Inc. 
London: Kegan Paul, Trench, Trubner & Co.,
Ltd. 
1922
</body>
</html>

Web Resource
A Book – Metadata elements
Title
Author
Publisher
Date
Contributor

Four principles to add machine readable data
1. Identify resources
2. Reuse ontologies
3. Express meaning
4. Link to other Web resources

Semantic Web
– Uniquely assign a Uniform Resource
Identifier (URI) to every Web resource

Title
Author
Publisher
Date
Contributor
Web Resource
http://example.org/book/Tractatus_Logico-Philosophicus

Semantic Web
2. Reuse Ontologies
– Specification of a conceptualization,
ie. a description of the concepts and
relationships in a domain
– Link to information in ontologies by
their URI to reuse the same
definition of common concepts, such
as the "book" or the "title“

Title
Author
Publisher
Date
Contributor
Web Resource
2. Reuse ontologies – e.g. Dublin Core
http://purl.org/dc/elements/1.1/creator
http://purl.org/dc/elements/1.1/date
http://purl.org/dc/elements/1.1/publisher
http://purl.org/dc/elements/1.1/contributor
http://purl.org/dc/elements/1.1/title

Semantic Web
3. Express meaning
– Add structured information and set
of rules to Web resources
– Use knowledge representation
language – typically RDF
• statements about Web resources in the
form of Subject-Predicate-Object
(S P O) triples

Web Resource
3. Express meaning
dc:title
has a
which is

Web Resource
3. Express meaning
dc:creator
has a
whose name is

Web Resource
3. Express meaning
dc:contributor
has
a
whose name is

Web Resource
3. Express meaning
dc:publisher
which is
has a

Web Resource
3. Express meaning
dc:date
has a
which is

@prefix dc: <http://purl.org/dc/terms/> .
@prefix : <http://example.org/book#> .
:Tractatus_Logico-Philosophicus dc:title "Tractatus Logico-Philospohicus" .
:Tractatus_Logico-Philosophicus dc:creator "Ludwig Wittgenstein" .
:Tractatus_Logico-Philosophicus dc:contributor "Bertrand Russell" .
:Tractatus_Logico-Philosophicus dc:publisher "Harcourt, Brace & Company, Inc." .
:Tractatus_Logico-Philosophicus dc:date "1922" .
Resulting triples
3. Express meaning

<?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF
xmlns:dc="http://purl.org/dc/terms/"
xmlns="http://example.org/book#"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
<rdf:Description rdf:about="http://example.org/book#Tractatus_Logico
Philosophicus">
<dc:title>Tractatus Logicao-Philospohicus</dc:title>
<dc:creator>Ludwig Wittgenstein</dc:creator>
<dc:contributor>Bertrand Russell</dc:contributor>
<dc:publisher>Harcourt, Brace & Company, Inc.</dc:publisher>
<dc:date>1922</dc:date>
</rdf:Description>
</rdf:RDF>
Resulting triples in RDF/XML
3. Express meaning

Semantic Web
– Progressively link to existing Web
resources that someone else has
defined already

Web Resource
dc:creator
has a
whose name is

Web Resource
dc:creator
has a
http://dbpedia.org/page/Ludwig_Wittgenstein
whose
name
is

RDF → for agents
RDF annotations often express
metadata (as in our book example)
– usually stored in a separate .rdf file
– useful for agents, limited use for humans

RDFa → for agents and humans
RDFa = RDF in attributes
– a way to mark up data in a web page
– RDFa encodes RDF triples in HTML
– useful for agents and (relatively) easy
to use for humans

HTML
<html>
<head>
<title>Tractatus Logico-Philosophicus</title>
</head>
<body>

<img src="tractatus.png" /> 
Written by: Ludwig Wittgenstein 
With an Introduction by: Bertrand Russell 
New York 
Harcourt, Brace & Company, Inc. 
London: Kegan Paul, Trench, Trubner & Co., Ltd. 
1922
</body>
</html>

RDFa example
<html prefix="dc: http://purl.org/dc/terms/“
base="http://example.org/book/Tractatus_Logico-Philosophicus">
<head>
<title about="" property="dc:title">Tractatus Logico
Philosophicus</title>
</head>
<body>

<img src="tractatus.png" /> 
Written by: Ludwig
Wittgenstein
 
With an Introduction by: 
Bertrand Russell 
New York 
Harcourt, Brace & Company, Inc.
 
London: Kegan Paul, Trench, Trubner & Co., Ltd. 
1922
</body>
</html>

RDFa – metadata vs. data
RDFa mostly used for metadata, e.g.
the book metadata as before
But: the principle of the Semantic
Web and Linked Data is to add
meaning to metadata and data
– Data could be metadata,
– but it could be data, e.g. a book
purchase at Amazon

Forms, metadata vs. data
e.g. Book purchase on Amazon
First Name:
Last Name:
Jane
Doe
Email: jane.doe@example.com
Password: ********
Gender:
Birthday: 03 04 1976
Male Female

1976
First Name:
Last Name:
Jane
Doe
Password: ********
Gender:
Birthday: 03 04
Male FemaleTitle:
Author:
Tractatus Logico Phi
Ludwig Wittgenstein
Price: 25 GBP
Amount: 1
Delivery
Address:
10 Downing Street
London
SW1A 2AA
United Kingdom

1976
First Name: Jane
Doe
Password: ********
Gender:
Birthday: 03 04
Male FemaleTitle:
Author:
Ludwig Wittgenstein
Price: 25 GBP
Amount:
1
Delivery
Address:
10 Downing Street
London
SW1A 2AA
United Kingdom
197604
1
Cardholder:
CC Number:
Expiry Date:
CVV: 999
Price:
Type: Mastercard
Jane Doe
5999 9999 9999 9999
04 13
25 GBP
Last Name:

197604
FemaleTitle:
Author:
Ludwig Wittgenstein
Price: 25 GBP
Amount: 1
Delivery
Address:
10 Downing Street
London
SW1A 2AA
United Kingdom
→ metadata
→ metadata
→ metadata / data
→ data
→ data
→ data
→ data
→ data

Issue – Adding RDFa for data to forms
Form input elements can be
annotated with RDFa
But: RDFa annotations for input data
is not possible → no binding

Issue – Adding RDFa for data to forms
e.g. “Jane” can not be defined as
foaf:firstName
First Name:
Last Name:
Jane
Doe
Password: ********
Gender:
Male Female

<input type="text" name=“First Name" value="" />
span>
No binding!

Making input data available on
the Semantic Web!

Model and System for semantic Web applications
– RDF-based model for forms (RaUL)
http://purl.org/NET/raul#
– RESTful Web service (ActiveRaUL)
http://raul.deri.ie/raul
– JavaScript RDFa API

RaUL form model
Defines meta model for form elements

RaUL form model
– Triples defining the structure of a form
– Triples defining the data
First Name:
Last Name:
Jane
Doe
Password: ********
Gender:
Male Female
→ foaf:firstName
→ foaf:surname
→ foaf:mbox
→ foaf:sha1
→ foaf:gender
→ time:day, time:month, time:year

ActiveRaUL Web service
Model-View-Controller
– Model: RaUL
– View: Rendering service
to generate RaUL-based
Web forms in
XHTML+RDFa
– Controller: Web service
that maps HTTP terms to
CRUD operations on RaUL
Web forms

JavaScript RDFa API
– Parses RDFa
– Manages data binding of form input
to data model

Lifecycle
1. Form Modeling:
form model in RDF
based on the RaUL
ontology
– Actor: ontology engineer

Lifecycle
2. Form Deployment:
form submitted by
calling ActiveRaUL
– Generic form models in a
public namespace →
standard form models
– Actor: ontology engineer

Lifecycle
3. Form Usage: access
and manipulate a form
model by calling
ActiveRaUL
– submit instance data for a
form → bound to a data
model
– Actor: Web user or agent

Lifecycle
4. Data Reuse: Add link
to existing, local data or
data in the Linked data
cloud
– RDFa API retrieves data
from that URI and prefills
form controls
– Actor: Form Provider

Conclusion
RDFa annotated Web forms which follow the
principles of Linked Open Data.
Advantages:
1. Non-ambiguous model: typed through an ontological
model.
2. RDF data submission: submitted data encoded in RDF.
3. Explicit form structure: form elements are explicitly
modelled as RDF statements.
4. External schema augmentation: reuse existing
schemas for form data
5. Reuse of Linked Open Data: retrieve data from the
Linked Open Data cloud

A Semantic Data Model for Web Applications

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