This page is a subpage of CMDI 1.2

Display Information 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/Display information.

Issue description

CMDI profiles provide the blueprint for a logical structuring of metadata instances. They provide very little information about how the information contained in the records should be presented (with the exception of the displayPriority attribute). It would be desirable to have some unified and extensible way of providing (sets of) display cues related to but physically separate from the description of the logical structure like (conceptually) CSS and XML.

Display aspects that might be included:

• Grouping information
  • Grouping of elements within components
  • Merging of components on one level
  • Merging of components contained within one other
• Salient element selection - an alternative/replacement for display priorities allowing the client to select one or elements representing the component in which they are contained for summarised display (e.g. in a tree).
• Field display mode reflecting importance

Description of proposed solution

A separate namespace is used for display cues (​http://www.clarin.eu/cmdi/cues/display/1.0). In this namespace attributes are defined (in an independent XSD) for all kinds of display and interaction cues. The general component specification allows any attributes from this namespace on all components, elements and attributes. To define a 'style' for a given component or profile, an XSLT stylesheet has to be created that augments the component specification with these cue attributes with the desired values.

The component-to-schema XSLT picks up all cues and wraps them in app info blocks in the profile XSD. When requesting a profile from the Component Registry, it can be instructed to apply a style (or maybe multiple), e.g. by getting /registry/profiles/clarin.eu:cr1:p_1361876010587/xsd?style=my_style where my_style is an identifier that gets the style from some style registry.

Notes:

• The style injects the namespace definition and schema location into the component spec which allows independent versioning of styles
• Applications can choose which cues to support and which not, and will also likely support a specific version of the style 'language'

The required infrastructure extensions will be developed at a later stage and are not part of the CMDI 1.2 specification.

General Component Schema changes

The following changes to the General Component Schema are proposed:

New xs:anyAttribute with namespace "​http://www.clarin.eu/cmdi/cues/display/1.0" for clarin_element_attributes, clarin_component_attributes and Attribute (? TODO):

• <xs:anyAttribute namespace="http://www.clarin.eu/cmdi/cues/display/1.0" processContents="strict"/>

Profile schema changes

The display cue attributes are inherited on the element and attributes definitions in the schema file.

Instance changes

There will be no changes to CMDI instances.

Impact on tools

There is no impact on tools as long as there is no agreement on details which are not part of this specification (about what kind of display information will be used/supported). If there is such an agreement the following changes would be necessary:

• Extension of the Component Registry with some kind of 'style registry' and "style editor'
• Extension of the Component Registry API with additional parameter ('style') to activate the augmentation of the component specification with style information
• Metadata editors and all CMDI viewers (like the VLO) may use this information for enhanced display (and may decide to use only a subset)