Download Vocabularies and Linked Data

Vocabularies and
Linked Data
IST 653
Benefits of Subject Headings
• Improves Resource Discovery
• Users can retrieve meaningful sets of digital objects
• Retrieve by:
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Type: Audio, Moving Image, Document
Format: .wav, .tif, .pdf
Place: Albany County (N.Y.)
Person: Cuomo, Mario M., 1932-2015
• Consistent terms are used for Names and Subjects
• There are many authorities
• Ontology and authority are used interchangeably
Authority control or
Controlled Vocabularies
• Organizes bibliographic information
• Dictates what you can put in the metadata field
• Uses one distinct spelling
• Names of people, places, things, and concepts
are authorized
• Facilitates browsing
• Subject and Name authorities were the only option
for searching before the rise of computerized
search indexes
• Decades long, tried and true method for organizing
information
Metadata, Vocabularies, Content,
Format
• Metadata Standard: structured information that
describes, explains, locates, or otherwise makes it
easier to retrieve, use or manage an information
resource ex. MARC, Dublin Core, EAD
• Content Standard: is a set of rules for describing
information DACS, RDA, AACR2
• Controlled Format: rules concerning the allowable data
types and formatting of information ISO ex. 2017-04-07
• Controlled Vocabulary: standardized list of terms that
been selected for consistent use in describing
information LCSH, SKOS,
Inconsistent Values for
Resource Type
• No consistency without control
• Creating unique entries
• Human users can make read it,
but computers cannot logically
• Computers very literal
• Nearly impossible to sustain or
migrate metadata into the
future
Equivalence relationship
Handles Hierarchy of terms
• A stricter form of vocabulary is a Thesaurus
• Broader terms
• Narrower terms
Spectrum of Controlled Vocabularies
Handles for Ambiguity &
Disambiguation
• Bank:
• (Financial Institution )
• (Container)
• (A mound of dirt)
Rise of Search
• Founded by Larry Page and Sergey Brin
• Many server farms
• Each composed of thousands of low-cost
computers running stripped-down
versions of Linux
• Google does not give out specifics on
how their process works
• Estimated more than 450,000 servers
around the world
Google’s Search
• Google knows the web is unstructured.
• Takes messy web, and creates orderly indexs
• Crawls web creates PageRank
• PageRank works by counting the number and quality of
links to a page to determine a rough estimate of how
important the website is. The underlying assumption is
that more important websites are likely to receive more
links from other websites
• Search, until now, is dominated by this paradigm.
Linked Data or Semantic Web
• Coined by Tim Berners-Lee and part of his original
plan for the World Wide Web
• Uses XML standard called Resource Description
Framework or RDF
• We are using XML, so isn’t the web already
understandable by computers?
• The Semantic Web was laid out in a famous article
published 2001 in Scientific American by Tim
Berners-Lee, James Hendler, and Ora Lassila
But, we have XML
• XML marked up web information and structured it
• Computers could read XML documents, and
restructure data, manipulate, update and delete
and send over the web safely
• XML allowed computers to “talk” to each other via
serialization.
• Before that, most documents were binary meaning
that each document needed the specific program
to run read the document
• For example, a Word document needed MS Word
to read it
Before Linked Data
• The web is linked together
• Lots of relationships
• Great for humans,
• We can link to images, charts, other documents
• But, computers don’t understand the relationships
like humans do
Linked Data
• Explicitly express things and relationships, like
names, birthdays, places, friend, parent, etc.
• Links to a name, like Frank in a website to another
person, Jan on another website etc.
• Frank knows Jan and she is parent of Tim
• Express it in a common format, using RDFa or
JSON-LD
• How do we do it:
• Authorities
• URIs
• Triples
Resource Description Framework
in Attributes (RDFa)
• XML based standard
• is a W3C Recommendation that adds a set of
attribute-level extensions to HTML, XHTML and
various XML-based document types for embedding
rich metadata within Web documents.
• XML /serialization is the physical format of data,
while the RDFa is a data model so that we can
represent the book's inherent meaning.
JSON for Linking Data
• JSON, or JavaScript Object Notation, is a minimal,
readable format for structuring data. It is used
primarily to transmit data between a server and
web application, as an alternative to XML.
• JSON-LD, or JavaScript Object Notation for Linked
Data, is a method of encoding Linked Data using
JSON
Triples
• Subject — The resource that’s being described. Book, person, LCSH,
website, function, anything that can be described can be a subject. This is
always a URI (uniform resource identifier) of some kind. That could be a
URL. It could also be another kind of identifier, such as an ISBN.2
• Predicate — Also known as a “property,” this is a URI which fulfills the role
of the database field name or the name of an XML tag. It declares what’s
going to be declared about an object. A very simple example would be
<dc:title> in XML. In RDF, this would be the equivalent of
<http://purl.org/dc/terms/title>, although it may sometimes even be
written as dc:title (see “Serialization” below)
• Object — The value of a statement. This can be a URI, like the other two,
or it can be what’s called a “Literal,” meaning a string, a number, or a
date, enclosed in quotation marks. Strings are what we normally think of
as text. We can get more specific about what this Literal is with datatype
and language modifiers (see “Datatype and Language Modifiers“).
Triple
Frank
Knows
Jan
Google Knowledge Graph
• We have auto complete, but that is using older
indexing technology
• Knowledge graph is using Linked Data to answer
questions for the user.
• https://www.google.com/