The current definition of CodeSystem.filter states that this element is intended to be used in a value set compose statement when selecting concepts using a filter, filter.code identifying the filter in ValueSet.compose.include.filter.

However, in the definition of the ValueSet.compose.include.filter element, nothing implies the possibility of leveraging CodeSystem.filter in this element. Instead, this definition references only CodeSystem.property.

The following element definitions should therefore be corrected:

• ValueSet.compose.include.filter:

Definition: Select concepts by specify a matching - criteria - * criterion *based on the properties (including relationships) defined by the system, * or on the filters defined by the system *. If multiple filters are specified, they SHALL all be true.

• ValueSet.compose.include.filter.property:

Definition: A code that identifies a property + or a filter + defined in the code system.

• ValueSet.compose.include.filter.op:

Definition: The kind of operation to perform as a part of the filter criteria. + In case filter.property represents a property of the system, the operation applies to the selected property. In case filter.property represents a filter of the system, the operation SHALL match one of the CodeSystem.filter.operator. +

• ValueSet.compose.include.filter.value

Definition: The match value may be either a code defined by the system, or a string value, which is a regex match on the literal string of the system property value * (if the filter represents a property defined in CodeSystem) or of the system filter value (if the filter represents a filter defined in CodeSystem) * when the operation is 'regex', or one of the values (true and false), when the operation is 'exists'.

Last, in the Examples tab, an example should be added to show how the intensional definition of a value set can rely on a filter defined in the underlying system. Because, this is not trivial at all.