Branch filtering: Multiple condition sets for a branch

Using multiple <ditavalref> elements as the children of a map or map branch indicates that the map or map branch must be conditionally processed using the rules that are specified in the referenced DITAVAL documents.

When multiple <ditavalref> elements occur as children of the same element, the rules in the referenced DITAVAL documents are processed independently. This effectively requires a processor to maintain one copy of the branch for each <ditavalref>, so that each copy can be filtered using different conditions.

Note: In most cases, it is possible to create a valid, fully-resolved view of a map with branches copied to reflect the different <ditavalref> conditions. However, this might not be the case when multiple <ditavalref> elements occur as direct children of a root map. In this case, it is possible that the map could be filtered in a manner that results in two or more distinct versions of the <title> or metadata. How this is handled is processor dependent. For example, when a root map has three <ditavalref> elements as children of <map>, a conversion to EPUB could produce an EPUB with three versions of the content, or it could produce three distinct EPUB documents.

When a processor maintains multiple copies of a branch for different condition sets, it has to manage situations where a single resource with a single key name results in two distinct resources. Key names must be modified in order to allow references to a specific filtered copy of the resource; without renaming, key references could only be used to refer to a single filtered copy of the resource, chosen by the processor. See Branch filtering: Impact on resource and key names for details on how to manage resource names and key names.

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