This International Standard specifies a number of metadata elements that describe resources containing medical knowledge, primarily digital documents provided as web resources, accessible from databases or via file transfer, but can be applicable also to paper documents, e.g. articles in the medical literature. The metadata elements: support unambiguous and international understanding of important aspects to describe a resource e.g. purpose, issuer, intended audience, legal status and scientific background; are applicable to different kinds of digital resources, e.g. recommendation from consensus of a professional group, regulation by a governmental authority, clinical trial protocol from a pharmaceutical company, scientific manuscript from a research group, advice to patients with a specific disease, review article; are possible to present to human readers including health professionals as well as citizens/patients are potentially usable for automatic processing e.g. to support search engines to restrict matches to documents of a certain type or quality level. The metadata elements defined in this International Standard are not intended to: describe documents about a single patient, such as medical records; describe details of the medical content of the resource (but some idea of the content can be described via keywords or codes); prescribe criteria for the quality of the resource content.