The Semantic Web encompasses the technology that connects data from different sources across the Web as envisioned by Tim Berners-Lee and led by the World Wide Web Consortium (W3C). This Web of Data enables the linking of data sets across data silos on the Web by providing for machine-to-machine communication through the use of Linked Data. This Guide provides descriptions and links to resources used to implement this technology.
The UCLA Semantic Web LibGuide was compiled and written by Rhonda Super. It began as a data page on Ms. Super's personal resource home page. Over a twenty year period, the Semantic Web resources listed on Rhonda's Resource Page developed into a stand alone LibGuide that served as a comprehensive resource for the Semantic Web and Linked Data community providing links to tools, best standards, instructional materials, use cases, vocabularies, and more.
The Guide was updated continuously through August 2022 using the SpringShare LibGuide platform as customized by the UCLA Library. Many of its resources provide a historical look at the development of Linked Data.
Ms. Super holds a BA in English and Government and an MA in Communications from Ohio University. She earned her MLIS from San Jose State University with a concentration in archives, rare books, and academic libraries. She earned a Certificate in XML and RDF Systems from the Library Juice Academy. Ms. Super was awarded scholarships to attend the California Rare Book School where she studied Rare Books for Scholars and Archivists, Descriptive Bibliography, and History of the Book: Nineteenth and Twentieth Centuries. Ms. Super was employed by the UCLA Library from 2007 until her retirement in 2022.
The final iteration of the Guide is deposited in the University of California eScholarship Open Access repository so the Linked Data community can continue to use it as a resource.
If you cite resources from this Guide, please check the original resource for copyright and citation requirements.
Scroll down the page to access the topics listed below.
The Semantic Web provides for the ability to semantically link relationships between Web resources, real world resources, and concepts through the use of Linked Data enabled by Resource Description Framework (RDF). RDF uses a simple subject-predicate-object statement known as a triple for its basic building block. This provides a much richer exploration of Web and real world resources than the Web of Documents to which we are accustomed.
The diagram on this page is a visualization of Linked Open Datasets published in the Linked Data format as of April, 2014. The large circle in the center is Dbpedia, the linked data version of Wikipedia. Click on the diagram to learn more about the diagram, licensed and open linked data, statistics about the datasets in the diagram, and the latest version of the LOD Cloud. As of June, 2018, you can view Sub-CLouds by subject area.
Linking Open Data cloud diagram 2014, by Max Schmachtenberg, Christian Bizer, Anja Jentzsch and Richard Cyganiak.
Trust is a major component of the Semantic Web. This requires providing accurate information when publishing a Linked Data instance. The World Wide Web Consortium (W3C), comprised of an international community, develops Web standards and best practices. Additionally, authorities in subject disciplines establish, administer, and maintain standards in their disciplines which adhere to W3C best practices.
This page provides access to information regarding best practices and standards relevant to Semantic Web technology as developed by W3C and other authoritative bodies. For controlled vocabularies, ontologies, etc., please consult the Vocabularies, Ontologies & Fameworks page.
A metadata application profile (MAP) is a set of recorded decisions about a shared application or metadata service, whether it is a datastore, repository, management system, discovery indexing layer, or other, for a given community. MAPs declare what types of entities will be described and how they relate to each other (the model), what controlled vocabularies are used, what fields are required and which fields have a cap on the number of times they can be used, data types for string values, and guiding text/scope notes for consistent use of fields/properties.
A MAP may be a multipart specification, with human-readable and machine-readable aspects, sometimes in a single file, sometimes in multiple files (e.g., a human-readable file that may include input rules, a machine-readable vocabulary, and a validation schema).
The function of a MAP is to clarify the expectations of the metadata being ingested, processed, managed, and exposed by an application or service and document shared community models and standards, and note where implementations may diverge from community standards.
Cornell University Library. (2018, October 23).CUL Metadata Application Profiles. Downloaded January , 2020, from
Library of Congress. (2019, April 30). PCC Task Group on Metadata Application Profiles. Downloaded July 19, 2022 from https://confluence.cornell.edu/display/mwgweb/CUL+Metadata+Application+Profiles
Below is a list of books which provide a good introduction to the Semantic Web. Items whose titles are highlighted in blue link either to the UCLA Library record for that title if the tile is held by the library, or to an online copy if available. Use the Safari Books Online link to search for additional resources.
There are many resources available to help you learn about the Semantic Web and Linked Data. This page provides access to a few instructional resources on topics relating to Linked Data in a variety of formats. See the SPARQL page for SPARQL related instructional resources.
Semantic Web technology uses an array of tools. This page lists conversion tools, data management tools, glossaries, ontology & vocabulary building platforms, Semantic Web browsers, validators, XML editors, and XPath tools.
SPARQL serves as the search engine for RDF. It is a set of specifications recommended by W3C Recommendation that provide languages and protocols to query and manipulate RDF graph content on the Web or in an RDF triple store.
In addition to the W3c SPARQL documents, there is documentation for a Geospatial SPARQL query language.
This box provides links to some SPARQL endpoints that are useful for researchers, and are good examples of datasets to practice using SPARQL queries. The Europeana dataset is used in the SPARQL for humanists tutorial on the left.
This box contains SPARQL tools.
Controlled vocabularies, ontologies, schemas, thesauri, and syntaxes are building blocks used by Resource Description Framework (RDF) to structure data semantically, identify resources, and to show the relationships between resources in Linked Data. Libraries and cultural institutions belong to one of the many knowledge organization domains making use of controlled authorities. These pages focus especially on the vocabularies and computer languages that are used in the library and cultural heritage institutions data landscape.
Becker, Devin and Jenn L. Riley. (2010). Seeing Standards: A Visualization of the Metadata Universe. Click on the chart to access a PDF version and a Glossary of Metadata Standards.
International Image Interoperability Framework (IIIF)
IIIF is a framework for image delivery developed by a community of leading research libraries and image repositories. The goals are to provide access to an unprecedented level of uniform and rich access to image-based resources hosted around the world, define a set of common application programming interfaces supporting interoperability between image repositories, develop, cultivate and document shared technologies, such as image servers and web clients, for providing viewing, comparing, manipulating, and annotating images.
The two core APIs for the Framework are:
IIIF Consortium. (2021). Appleby, Michael, Crane, Tom, Sanderson, Robert, Stroop, Jon, and Warner, Simeon. This document describes an image delivery API specification for a web service that returns an image in response to a standard HTTP or HTTPS request. The URI can specify the region, size, rotation, quality characteristics and format of the requested image as well as be enabled to request basic technical information about the image to support client applications.
IIIF Consortium. (2021). Appleby, Michael, Crane, Tom, Sanderson, Robert, Stroop, Jon, and Warner, Simeon. The IIIF Presentation API provides information necessary to human users to allow a rich, online viewing environment for compound digital objects. It enables the display of digitized images, video, audio, and other content types associated with a particular physical or born-digital object, allows navigation between multiple views or time extents of the object, either sequentially or hierarchically, displays descriptive information about the object, view or navigation structure, and provides a shared environment in which publishers and users can annotate the object and its content with additional information.
The Cookbook provides resource types and properties of the Presentation specification and for rendering by viewers and other software clients. Examples are provided to encourage publishers to adopt common patterns in modeling classes of complex objects, enable client software developers to support these patterns, for consistency of user experience, and demonstrate the applicability of IIIF to a broad range of use cases.
Additional APIs for the Framework are:
IIIF Consort ium. (2021). Appleby, Michael, Crane, Tom, Sanderson, Robert, Stroop, Jon, and Warner, Simeon.The Authentication specification describes a set of workflows for guiding the user through an existing access control system. It provides a link to a user interface for logging in, and services that provide credentials, modeled after elements of the OAuth2 workflow acting as a bridge to the access control system in use on the server, without the client requiring knowledge of that system.
IIIF Consort ium. (2021). Appleby, Michael, Crane, Tom, Sanderson, Robert, Stroop, Jon, and Warner, Simeon. The Content Search specification lays out the interoperability mechanism for performing searches among varied content types from different sources. The scope of the specification is searching annotation content within a single IIIF resource, such as a Manifest, Range or Collection.
Linked Art is a data model which provides an application profile used to describe cultural heritage resources, with a focus on artworks and museum-oriented activities. Based on real world data and use cases, it defines common patterns and terms used in its conceptual model, ontologies, and vocabulary. Linked Art follows existing standards and best practices including CIDOC-CRM, Getty Vocabularies, and JSON-LD 1.1 as the core serialization format.
Ontologies are formalized vocabularies of terms, often covering a specific domain. They specify the definitions of terms by describing their relationships with other terms in the ontology. OWL 2 is the Web Ontology Language designed to facilitate ontology development and sharing via the Web. It provides classes, properties, individuals, and data values that are stored as Semantic Web documents. As an RDF vocabulary, OWL can be used in combination with RDF schema.
Negru,Stefan, Lohmann, Seffan, and Haag, Florian. (2014, April 7). Specification of Version 2.0. VOWL defines a visual language for user-oriented representation of ontologies. The language provides graphical depictions for elements of OWL that are combined to a force-directed graph layout visualizing the ontology. It focuses on the visualization of the classes, properties and datatypes, sometimes called TBox, while it also includes recommendations on how to depict individuals and data values, the ABox. Familiarity with OWL and other Semantic Web technologies is required to understand this specification.
The Resource Description Framework (RDF) is a framework for representing information in the Web of Data. It comprises a suite of standards and specifications whose documentation is listed below.
RDF 1.1 Serializations
There are a number of RDF serialization formats for implementing RDF. The first format was XML/RDF. Subsequent serialization formats have been developed and may be more suited to particular environments.
SKOS (Simple Knowledge Organization System)
SKOS is a W3C data model defined as an OWL Full ontology for use with knowledge organization systems including thesauri, classification schemes, subject heading systems, and taxonomies. Many Semanatic Web vocabularies incorporate the SKOS model. The Library of Congress Subject Headings and the Getty Vocabularies are an examples of vocabularies published as SKOS vocabularies.
A schema uses a formal language to describe a database system and refers to how the organization of data in a database is constructed. Several schemas addressing varied domain areas are listed in this box. Scroll down to the Dublin Core box to access information regarding the Dublin Core schema and tools.
Vocabulary of Interlinked Datasets (VoID)
For the Getty Vocabularies, please see the Registries, Portals, and Authorities page.
Wikibase is the platform on which Wikidata, A Wikimedia Project, is built. It allows for multi-language instances. For Wikibase Use Cases, see the Wikibase Use Case box on the bottom of the Use Cases page.
Wikimedia is a global movement that seeks to bring free education to the world vai websites known as Wikimedia Projects. Wikimedia Projects are hosted by the Wikimedia Foundation. Some of these Projects are listed below. Access the full family of Wikimedia Projects here.
Wikidata is a free, collaborative, multilingual software application built from Wikibase components that can be read and edited by humans and machines. It collects structured data to provide support for Wikimedia Projects including Wikipedia, Wikimedia Commons, Wikivoyage, Wiktionary, Wikisource, and others. The content of Wikidata is available under a free license, exported using standard formats, and can be interlinked to other open data sets on the linked data web.
There are many tools developed for working with Wikidata, many which are listed on the Wikidata Tools page listed below. General tools that are helpful with editing and adding items to Wikidata are listed here.
This page provides access to documents and reports associated with workshops, institutions, organizations, or other entities which relate valuable information, or describe initiatives or projects regarding the Semantic Web or Linked Data.
This page provides links to examples of Linked Data currently in use.