1. Remove the Classification back bone element from the ResearchStudy resource
2. Add a new element to base researchStudy resource
Name: classifier
Cardinality: 0..*
Data type: codeableConcept
Definition: Additional grouping mechanism or categorization of a research study. Example: type of blinding, type of randomization, etc. Implementation Note: do not use the classifier element to support existing semantics that are already supported thru explicit elements in the resource.