This page is a subpage of CMDI 1.2

Derived Values in CMDI 1.2: Executive summary

This page provides an executive summary of the issue and proposed solution fully described in CMDI 1.2/Cues/Derived values.

Issue description

Most parts of a metadata record need to be created manually but in some cases parts of it can be derived: either from the described resource (mostly technical details) or from other metadata values, sometimes in combination with external data. The actual derivation of values woud have to be carried out by the tool (i.e. the editor).

Some examples of rules that might be supported are current date, file size (of the described resource), language name (from a filled in language code), actor age (based on birth of date and current date).

Description of proposed solution

The General Component Schema is extended with one additional optional attribute (AutoValue) for the element/attribute specification. This attribute contains a keyword that is used by the metadata generator or editor to generate the content of the respective element/attribute.

The supported attribute only provides a "hook" to extend CMDI components with a derivation functionality. There will be no concrete specification of supported functions, syntax or of the mechanism to reference content of other elements in the CMDI 1.2 specification. Rather, the specific implementation and coordination thereof is left to the (development) community.

General Component Schema Changes

The following changes to the General Component Schema are proposed:

New attribute for clarin_element_attributes and Attribute (assuming the attribute definition gets normalised):

• @AutoValue (optional: Derivation function with arguments)

Profile schema changes

The changes to the General Component Schema reflect in the CMDI Profile Schema as follows:

Attribute for xs:element and xs:attribute:

• @AutoValue? (optional: Derivation function with arguments)

Instance changes

There will be no changes to CMDI instances.

Impact on tools

• Component Registry must support adding derivation keywords (as free text) to elements/attributes.
• Metadata editors should provide support for keywords. Specifically this means that editors should automatically insert values for elements/attributes if applicable.