2. Outline
• Why we need Semantic web?
• Linked Open Data
• Open Data
• Linked Data
• How does it work?
• The important of Linked Open Data
• Disadvantages of Linked Open Data
• Accessing Linked Open Data Sets
• Publishing Linked Open Data
• Consuming Linked Open Data
3. Why we need Semantic web?
• The World Wide Web facilitates the global information space
by comprising the linked documents.
• The current web is mainly concern the presentation of data.
They are links the HTML pages or documents. But machines
have no way to understand these documents and cannot
make any intelligent decision about these documents.
• We need to help machines to understand the web so
machines can help us understand things
• They can learn what we are interested in
• They can help us better find what we want
4. Why we need Semantic web?
• So need to publish something that computers can understand.
• The semantic web isn‘t just about putting data on the web . It
is about making links, so that a person or machine can explore
the semantically connected web of data.
• Semantic web goes beyond the concept of document and links
structured data. With Linked Open Data, can find more
related data than traditional web.
• Nowadays World Wide Web moving from the a Web of hyper-
linked Documents to opening up and interlinking data.
5. Linked Open Data
• What is Linked Open Data?
• Open Data + Linked Data = Linked Open Data
7. Open Data
• Open data is the data that should be freely available to
everyone to use and republish as they wish, without
restrictions from copyright, patents or other mechanisms
of control
• Data must also be available in a convenient and
modifiable form
• Everyone must be able to use,
reuse and redistribute
9. Linked Data
• “A method of publishing structured data so that it can be
interlinked and become more useful.
• It builds upon standard Web technologies such as HTTP,
RDF and URIs, but rather than using them to serve web
pages for human readers, it extends them to share
informal on in a way that can be read atomically by
computers.
• This enables data from different sources to be connected
and queried”
• [Bizer, Heath, Berners--‐Lee 2009]
10. Linked Data
• The Semantic Web isn't just about putting data on the web. It
is about making links, so that a person or machine can explore
the web of data.
• With linked data, when we have some of it, you can find other,
related data.
• Linked Data builds directly on Web architecture and applies
this architecture to the task of sharing data on global scale.
• Tim Berners-Lee’s introduced four principles on Linked Data
as best practices for publishing and interlinking structured
data on the Web.
11. Linked Data Principles
1. Use URIs as names for things
2. Use HTTP URIs so that people can look up those
names.
3. When someone looks up a URI, provide useful
information, using the standards (RDF*, SPARQL)
4. Include links to other URIs so that they can discover
more things
12. Use URIs as names for things
• The Web is an information space in which the items of
interest, referred to as resources, are identified by global
identifiers called Uniform Resource Identifiers (URI).
• Use URIs references to identify, not just Web documents and
digital content, but also real world objects and abstract
concepts.
• To publish data on the Web, the items in a domain of interest
must first be identified. These are the things whose properties
and relationships will be described in the data, and may
include Web documents as well as real-world entities and
abstract concepts.
• If it doesn't use the universal URI set of symbols, we don't call
it Semantic Web.
13. Use URIs as names for things
URIs are used to identify people and the relationships between
them.
14. HTTP URIs
• The HTTP protocol is the Web’s universal access mechanism
• Use HTTP URIs to identify objects and abstract concepts, enabling
these URIs to be dereferenced over the HTTP protocol into a
description of the identified object or concept.
• HTTP URIs make good names for two reasons:
• They provide a simple way to create globally unique names in a decentralized
fashion, as every owner of a domain name, or delegate of the domain name
owner, may create new URI references.
• They serve not just as a name but also as a means of accessing information
describing the identified entity.
• It’s all about interoperability
• The RDF data model uses URIs only as logical names.
15. Return information using the
standards
• When someone looks up a URI, provide useful information, using the
standards (RDF*, SPARQL)
• In order to enable a wide range of different applications to process
Web content, it is important to agree on standardized content
formats.
• use of a single data model for publishing structured data on the Web
– the Resource Description Framework (RDF), a simple graph-based
data model that has been designed for use in the context of the Web
• As the resulting Web of Data is based on standards and a common
data model, it becomes possible to implement generic applications
that operate over the complete data space
16. links to other URIs
• Include links to other URIs so that they can discover more things
• When applications can follow these links, they can find interesting
new things
• This links are expressed through a triple whose subject and object
live in different datasets.
• Links across the boundaries of datasets support the reuse, the
integration and the discovery of data
• Hyperlinks in the Linked Data context are called RDF links in order to
distinguish them from hyperlinks between classic Web documents.
18. Linked Open Data
• Linked open data is linked data that is open content.
• Open Data refers to data freely available without any
restrictions. Linked Data refers to semantically linked
machine-readable data.
• Therefore data can be open but not linked or linked but
not open, however if data is open and linked it then
becomes Linked Open Data.
• The example for large Linked Open Data is DBpedia.
19. Linked Open Data project
• Linked Open Data facilitates innovation and knowledge creation
from interlinked data, it is an important mechanism for information
management and integration.
• To fully benefit from Open Data, it is crucial to put information and
data into a context that creates new knowledge and enables
powerful services and applications.
• The goal of the W3C SWEO Linking Open Data community project is
to extend the Web with a data commons by publishing various open
data sets as RDF on the Web and by setting RDF links between data
items from different data sources.
• Linked Open Data makes the web appear as one giant huge global
database
21. 5-star rating scheme
• ★ - Data available on the web in any format, even using PDF
or image scan, but with an Open license.
• ★★ - Data delivered as machine-readable structured data
• ★★★-Data available in a non-proprietary format
• ★★★★ - All the above plus, data using open standards from
W3C, e.g. RDF and SPARQL, to identify things and properties,
so that people can point at other data
• ★★★★★- All the above, plus, to link data to other people’s
data to provide context
22. How does it work?
• Use Resource Description Framework (RDF) to linked data
across web.
• Resource Description Framework (RDF) enables meaning of
connection between the items distributed across the web.
• RDF is based on the idea of declaring resources using the
expression in the form subject-predicate-object. This form is
known as RDF triple.
• To create Linked Open Data it is necessary to create automatic
links between RDF triple stores on the web
23. Importance of Linked Open
Data
• If all the data on the Web were open and linked, it would be
easier to establish information systems combining different
distributed data repositories
• Linked Open Data enable access and sharing of data and
knowledge without barriers.
24. Disadvantages of Linked Open
Data
• Usages of Linked Data increases therefore some the data
available might be either irregularly updated, or already
available in other formats and APIs might become an issue
• Lack of applications and tools to exploit Linked Data.
• Existing open issues make the development of Linked Data
based applications a challenge, due to the difficulties to
integrate data in different formats and from multiple sources,
the discovery of data or the usability of user interfaces.
25. Publishing Linked Open Data
• Publishing Linked Open Data provides a powerful mechanism
for sharing your own data and information along with your
metadata and the respective data models for efficient re-use.
• The essential steps to publishing your own LOD are:
• Identify & analyze your data
• Clean the data
• Model your data (URI schema, vocabularies)
• Select & specify license(s)
• Convert data to RDF
• Link your data to other data
• Publish and promote your Linked Open Data
27. Consuming Linked Open Data
• Consuming LOD enables you to integrate and provide high
quality information and data collections to mix your own data
and third party information.
• Organizations can benefit and reach competitive advantage
through the possibility to:
• spontaneously generate dossiers and information mash ups from
distributed information sources;
• create applications based on real time data with less replication;
• create new knowledge out of this interlinked data.
28. Consuming Linked Open Data
• most important issues and milestones to consider when
consuming LOD:
1. Specify concrete use cases
2. Evaluate relevant data sources and data sets
3. Check the respective licenses
4. Create consumption patterns
5. Manage alignment, caching and updating mechanisms
6. Create mash ups, GUIs, services and applications on top
7. Establish sustainable new partnerships
29. Consuming LOD from LOD
players
• UK Organograms:http://data.gov.uk/organogram/hm-treasury
30. Consuming LOD from LOD
players
• reegle.info country profiles: http://www.reegle.info/countries
31. Linked Data Publishers
• UK Government
• US Government
• BBC
• Open Calais – Thomson Reuters
• Freebase
• NY Times
• Best Buy
• CNET
• Dbpedia
