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A ContentElement fills a ContentBlock in a ContentTemplate.
A ContentElement is usually embedded in the template with unique delimiting Tags. All CM systems have developed their own unique tags. Generally they followed the tag style of their underlying application FrameWork.
Interoperability? efforts are directed toward tags that use XML-style delimiters and names that can be found in an XML namespace and an Ontology. The DublinCore is the most widely used ontology.
Since a ContentBlock may be using a ContentTemplate, there can be an infinite recursion of containers. These are sometimes called Portlets?.
When a ContentBlock contains a single piece of elementary content (a simple link, text, an image, audio, video, a piece of metadata like author, title, etc.), we call it a ContentElement.
The ContentElement encourages ReUse.
Editing a ContentElement will change all its appearances. A new version of a ContentElement for special use is called a Derivative.
ContentElement versioning and other MetaData (e.g., scheduling information and usage permissions) can regulate Reuse.
A ContentElement is sometimes called Microcontent.
RT - ContentBlock, ContentTemplate
VT? - ContentItem?, ContentUnit?
Up to CmsGlossary.