Linked data MLA 2015

Linked Data,
the Semantic Web, and You
Maine Library Association 2015

What is Linked Data
Linked Data refers to a set of best practices for publishing
and connecting structured data on the Web.
URIs - Uniform Resource Identifiers
HTTP - Hypertext Transfer Protocol
RDF - Resource Description Framework
Source: http://linkeddata.org/faq

URIs
Uniform Resource Identifier (URI) is a string of characters used to identify the name of a resource.
Such identification enables interaction with representations of the resource over a network,
typically the World Wide Web, using specific protocols.
Uniform Resource Locator (URL) (commonly informally referred to as a web address, although
the term is not defined identically) URL (uniform resource locator) is a subset of the URIs that
include a network location.
Uniform Resource Name (URN) is a subset of URIs that include a name within a given space, but
no location.
Image Source: http://www.slideshare.net/rodsenra/rest-representational-state-transfer-emc-brdc-internal-tech-talk

HTTP
HyperText Transfer Protocol, HTTP is the underlying
protocol used by the World Wide Web. HTTP defines
how messages are formatted and transmitted, and what
actions Web servers and browsers should take in
response to various commands.

RDF
The Resource Description Framework (RDF) data model
represents information as node-and-arc-labeled directed
graphs. The data model is designed for the integrated
representation of information that originates from
multiple sources, is heterogeneously structured, and is
represented using different schemata. RDF aims at
being employed as a lingua franca, capable of
moderating between other data models that are used on
the Web.
Source: http://linkeddatabook.com/editions/1.0/#htoc16

Graph Database
Steven Roman
foaf:
knows
foaf:
publications
foaf:
publications
Dragons in the Stacks
Cason Snow

RDF - Triples
RDF uses triples to describe resources.
Triples consist of a Subject, Predicate, and Object.
Cason Snow knows Steven Roman.
http://www.library.umaine.edu/staff/snow.htm http://xmlns.com/foaf/0.1/knows https://dkpl.org/teens-tweens/

Serialization
Remember RDF is not a data format. It is a data model for
describing resources.
To display RDF data on the Web it must be serialized
though some kind of syntax.
RDF/XML and RDFa are standardized by the W3C but
many other serializations are out there.

RDF/XML example
1 <?xml version="1.0" encoding="UTF-8"?>
2 <rdf:RDF>
3 xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
4 mlns:foaf="http://xmlns.com/foaf/0.1/">
5 <foaf:Person>
6 <foaf:name>Cason Snow</foaf:name>
7 <foaf:workplaceHomepage rdf:resource=”http://www.library.umaine.edu/staff/snow.htm”/>
8 <foaf:knows>
9 <foaf:Person>
10 <foaf:name>Steven Roman</foaf:name>
11 <foaf:workplaceHomepage rdf:resource=”https://dkpl.org/teens-tweens/”/>
12 </foaf:Person>
13 </foaf:knows>
14 </foaf:Person>
15 </rdf:RDF>

Turtle (Terse RDF Triple
Language) example
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
a foaf:Person ;
foaf:name "Cason Snow" ;
foaf:workplaceHomepage <http://www.library.umaine.edu/staff/snow.htm> ;
foaf:knows [
a foaf:Person ;
foaf:name "Steven Roman"
] .

Benefits of RDF
in Linked Data
1. By using HTTP URIs as globally unique identifiers for data items as well as for vocabulary terms, the RDF data model is
inherently designed for being used at global scale and enables anybody to refer to anything.
2. Clients can look up any URI in an RDF graph over the Web to retrieve additional information. Thus each RDF triple is part
of the global Web of Data and each RDF triple can be used as a starting point to explore this data space.
3. The data model enables you to set RDF links between data from different sources.
4. Information from different sources can easily be combined by merging the two sets of triples into a single graph.
5. RDF allows you to represent information that is expressed using different schemata in a single graph, meaning that you
can mix terms for different vocabularies to represent data.
6. Combined with schema languages such as RDF-Schema and OWL, the data model allows the use of as much or as little
structure as desired, meaning that tightly structured data as well as semi-structured data can be represented.

Why Linked Data
Linked Data provides a more generic, more flexible publishing paradigm which makes it easier for
data consumers to discover and integrate data from large numbers of data sources. In particular,
Linked Data provides:
• A unifying data model
• A standardized data access mechanism
• Hyperlink-based data discovery
• Self-descriptive data

Semantic Web
Bringing Data to the Web

What is the Semantic Web
The ultimate goal of the Web of data is to enable computers to do more useful
work and to develop systems that can support trusted interactions over the
network.
Semantic Web technologies enable people to create data stores on the Web,
build vocabularies, and write rules for handling data.
Linked data are empowered by technologies such as RDF, SPARQL, OWL,
and SKOS.
Source: http://www.w3.org/standards/semanticweb/

Linked Data
The Semantic Web is a Web of data — of dates and titles and part numbers
and chemical properties and any other data one might conceive of. RDF
provides the foundation for publishing and linking your data.

Vocabularies
At times it may be important or valuable to organize data. Using OWL (to build
vocabularies, or “ontologies”) and SKOS (for designing knowledge
organization systems) it is possible to enrich data with additional meaning,
which allows more people (and more machines) to do more with the data.
Vocabularies are the contextless list of terms used
Ontologies provide the relationships and grammar to express relations
between vocabulary terms

Ontology Examples
Dublin Core
FOAF
WOT
Basic Geo Vocabulary

Query
Query languages go hand-in-hand with databases. If the Semantic Web is
viewed as a global database, then it is easy to understand why one would
need a query language for that data. SPARQL is the query language for the
Semantic Web.

Inference
Near the top of the Semantic Web stack one finds inference — reasoning
over data through rules. W3C work on rules, primarily through RIF and
OWL, is focused on translating between rule languages and exchanging
rules among different systems.

And You
BIBFRAME and Linked Data Library Projects

BIBFRAME
BIBFRAME (Bibliographic Framework Initiative) is a project by LC to provide a
foundation of bibliographic description for integration in the Web of Data.
Uses RDF serialization.

BIBFRAME
The BIBFRAME Model consists of the following main classes:
Creative Work - a resource reflecting a conceptual essence of the cataloging
item.
Instance - a resource reflecting an individual, material embodiment of the
Work.
Authority - a resource reflecting key authority concepts that have defined
relationships reflected in the Work and Instance. Examples of Authority
Resources include People, Places, Topics, Organizations, etc.
Annotation - a resource that decorates other BIBFRAME resources with
additional information. Examples of such annotations include Library
Holdings information, cover art and reviews.

Creative Work
The Work exists as a Web based control point that reflects both commonality
of content between and among the various Instances associated with the
Work as well as a reference point for other Works. Common properties of
Works include contextual relationships to BIBFRAME Authorities related to
the “subjectness” (Topic, Person, Place, Geographical, etc.) of the resource
as well as the entities (Person, Organization, Meeting, etc.) associated with
its creation. Works can relate to other Works reflecting, for example, part /
whole relationships.

Instance
BIBFRAME Instances reflect an individual, material embodiment of a
BIBFRAME Work that can be physical or digital in nature. A BIBFRAME
Instance exists as a Web based control point that includes properties
specific to the materialization as well as contextual relationships to
appropriate BIBFRAME Authorities related to the publication, production,
distribution of the material resource. Each BIBFRAME Instance is an
instance of one and only one BIBFRAME Work.

Authorities
BIBFRAME Authorities are key authority concepts that are the target of
defined relationships reflected in the Work and Instance. Example of
BIBFRAME Authority Resources include People, Places, Topics,
Organizations, etc. From a cataloging perspective Authorities provide a
means for supporting disambiguation and synchronization around
authoritative information. From a users perspective, BIBFRAME Authorities
provide effective and efficient control points that can be used to help
navigate and contextualize related BIBFRAME Works and Instances.
BIBFRAME Authorities are not designed to compete or replace existing
authority efforts but rather provide a common, light weight abstraction layer
over various different Web based authority efforts to make them even more
effective.

Annotation
Libraries generate, maintain and improve an enormous amount of high-quality
data that is valuable well beyond traditional library boundaries. The
Bibliographic Framework Initiative recognizes this by including as a goal the
ability to “accommodate and distinguish expert-, automated-, and self-
generated metadata, including annotations (reviews, comments) and usage
data.” Rather than pre-define and limit our potential uses of this data, the
BIBFRAME model provides the necessary scaffolding to allows this data to
easily be annotated by libraries as well as third party users of this
information.

BIBFRAME and MARC
BIBFRAME is not ready yet, and it will be a mixed environment for the near
future.
Currently there is a tool to convert MARC to BIBFRAME. It changes fairly
often as BIBFRAME develops.
Currently designed to be rules agnostic, but RDA is a major component.

Digital Public Library
of America
The Digital Public Library of America (DPLA) is an all-digital library that aggregates metadata — or
information describing an item — and thumbnails for millions of photographs, manuscripts, books,
sounds, moving images, and more from libraries, archives, and museums around the United
States. DPLA brings together the riches of America’s libraries, archives, and museums, and
makes them freely available to the world.

European Library
The European Library is an independent not-for-profit library services organisation supported by
CENL, LIBER and CERL. The European Library importantly works to strengthen and support libraries
across the continent. Member libraries benefit from a powerful, low-cost aggregation structure enabling
a greater exposure of digital resources and bibliographic records. We collect, enrich and innovate with
libraries' data and content for the widest possible dissemination.
The European Library's mission is to be THE open data hub for library data in Europe.
Additionally, The European Library partakes in projects to create useful tools and a pan-European
infrastructure for librarians and researchers.

Linked Data for Libraries
LD4L
The goal of the project is to create a Scholarly Resource Semantic
Information Store (SRSIS) model that works both within individual
institutions and through a coordinated, extensible network of Linked Open
Data to capture the intellectual value that librarians and other domain
experts and scholars add to information resources when they describe,
annotate, organize, select, and use those resources, together with the
social value evident from patterns of usage.

Further resources
Reading
BIBFRAME
Primer
XML
RDF
Education
Certificate in XML and RDF-based Systems
W3Schools XML Tutorial

Contact information
Cason Snow
Metadata Librarian/Cataloger
University of Maine
207-581-1670

Linked data MLA 2015

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