Table 2.

Glossary of key terms and definitions used

Term	Definition
Metadata	Metadata can be defined as data about data. It can include aspects such as the creator of the data, time and date of creation, its purpose, etc. Several metadata standards and models have been proposed by standards organizations such as Health Level 7 (HL7) and World Wide Web Consortium (W3C).
Data element (DE)	A DE can be defined as an atomic unit of data with precise meaning and semantics that is built on standard structures having a unique meaning and distinct units or permissible values.3 An example of a DE is ‘person gender type’, where ‘male’ and ‘female’ can be permissible values.
Terminology	A terminology is the collection of terms and concepts and their use in a particular domain. It could be a simple list of terms describing a category, such as ‘body parts’.
Controlled vocabulary	A controlled vocabulary organizes a collection of terms to reduce ambiguity and facilitate information retrieval. They include subject indexing schemes, subject headings, thesauri and taxonomies.
Ontology	An ontology is a special type of terminology that provides a formal representation of knowledge based on a set of concepts in a particular domain, along with the relationships that exist between those concepts.
DE harmonization	DE harmonization is the process of comparing conceptual and logical data representation models to identify similarities and dissimilarities.
Value set	A value set can be defined as a list of possible values for a specific purpose. In the context of terminologies, a value set is a uniquely identifiable set of valid values that can be resolved at a given point in time to an exact set (collection) of codes, and are often used as permissible values for a DE.
Data dictionary	A data dictionary is a collection of descriptions of the data objects or items stored in a dataset or a database.