The following international standards give guidance (best practices, practical considerations) on how to construct and format controlled vocabularies and thesauri.
ANSI/NISO Z39.19-2005 (R2010) Guidelines for the Construction, Format, and Management of Monolingual Controlled Vocabularies
"Abstract: Presents guidelines and conventions for the contents, display, construction, testing, maintenance, and management of monolingual controlled vocabularies. It focuses on controlled vocabularies that are used for the representation of content objects in knowledge organization systems including lists, synonym rings, taxonomies, and thesauri."
ISO 25964 – the international standard for thesauri and interoperability with other vocabularies
Part 1 of the standard, published in 2011, covers all aspects of developing a thesaurus, monolingual or multilingual. It has replaced the previous standards ISO 2788 and ISO 5964. To encourage networking interoperability, it includes a data model and an XML schema for data exchange.
Part 2 of the standard, to be published in 2013, covers new ground not previously addressed in any standard. Its main aim is to encourage high quality information retrieval across networked resources that have been indexed with different vocabularies. It explains how to set up mappings between the concepts in such vocabularies, and other forms of complementary use."
Data models and schemas
SKOS (Simple Knowledge Organization System)
"Introduction: SKOS is an area of work developing specifications and standards to support the use of knowledge organization systems (KOS) such as thesauri, classification schemes, subject heading systems and taxonomies within the framework of the Semantic Web."
"SKOS—Simple Knowledge Organization System—provides a model for expressing the basic structure and content of concept schemes such as thesauri, classification schemes, subject heading lists, taxonomies, folksonomies, and other similar types of controlled vocabulary. As an application of the Resource Description Framework (RDF), SKOS allows concepts to be composed and published on the World Wide Web, linked with data on the Web and integrated into other concept schemes." (source)
OWL (Web Ontology Language)
"The W3C Web Ontology Language (OWL) is a Semantic Web language designed to represent rich and complex knowledge about things, groups of things, and relations between things. OWL is a computational logic-based language such that knowledge expressed in OWL can be exploited by computer programs, e.g., to verify the consistency of that knowledge or to make implicit knowledge explicit. OWL documents, known as ontologies, can be published in the World Wide Web and may refer to or be referred from other OWL ontologies. OWL is part of the W3C’s Semantic Web technology stack, which includes RDF, RDFS, SPARQL, etc." (source)
FOAF (Friend of a friend)
"FOAF (an acronym of friend of a friend) is a machine-readable ontology describing persons, their activities and their relations to other people and objects." (source)
Dublin Core Metadata Initiative Terms
A set of metadata types that libraries have used for years, and upon which other schemas are often based.
Based on Dublin Core, Schema.org is structured data used primarily to mark up web pages."Schema.org vocabulary can be used with many different encodings, including RDFa, Microdata and JSON-LD. These vocabularies cover entities, relationships between entities and actions, and can easily be extended through a well-documented extension model. Over 10 million sites use Schema.org to markup their web pages and email messages." (source)
IPTC Photo Metadata Standard
"The IPTC Photo Metadata Standard is the most widely used standard to describe photos, because of its universal acceptance among news agencies, photographers, photo agencies, libraries, museums, and other related industries. It structures and defines metadata properties that allow users to add precise and reliable data about images."