Revision of SNOMED CT post-coordination rules: from practice to theory (master thesis)

The master thesis about Post-coordination issues in SNOMED CT suggests solutions for some topics and a guideline for post-coordination of clinical procedures. The project was done in the department of medical informatics in Academic Medical Center ( under the tutorship of Ronald Cornet ( ) and Kathrin Dentler ( A paper based on the thesis will follow in the nearest months.

SNOMED CT post-coordination guideline for clinical procedures
* numbers in brackets denote corresponding chapter in the thesis.

1. According to the criterion of proper concept definition (4.2.2), identify the attributes that will fully specify the target concept. This step complies with the criteria of the “proper” concept definition and inferred from Frege’s principle ( In most of the cases, the attributes of the procedure should include |Method|, |procedure site|, also additional elements like |Procedure morphology|, |procedure device|, |substance| and so on. In case of diagnosis included in the concept, use |Procedure morphology| if possible, or |has focus| (
2. Find a candidate parent concept, under which the new concept will be created. The parent concept should be the closest with meaning to the new concept, also as specific as possible. There can be more than one concepts if combination approach is used.
3.1. Inspect the candidate parent concept attributes and the values and check the definition status of the candidate parent;
3.2. Modify the attributes list, if needed;
3.3. If the parent concept cannot be found, revise the she attributes (Step 1).
4. If the definition requires the target concept to have a parent concept(s), that is not pre-coordinated, create the ancillary parent concept(s) ( and classify the ontology.
5. Create the target concept. Depending on the specific case, the concept should be created either as a child concept added to the parent, or via combination. Fully describe the concept in FSN and add synonyms (Chapter 4.2.1).
6. Run reasoner.
7. Inspect the post-coordinated concept definition, including the inferred attributes.
8. If more concepts for the target values of qualification and/or refinement are missing in SNOMED CT, create them.
9. Add additional attribute-values and/or refine the appropriate attributes, if needed. When possible, fully define the concept including necessary and sufficient attributes (4.2.2).
10. If needed arrange or re-arrange the attributes into relationship groups (4.2.4).
11. If required, create sub-concepts of the target concept.
12. If the steps 7-11 required qualification, refinement, or creating additional concepts, run reasoner.
13. Check the equivalence of the concept to other concept(s). If equivalent concept is found, report the new synonym(s) (description of the candidate post-coordinated concept) to IHTSDO (
14. In case the intra-axiom redundancy (, modify or inactivate redundant attributes and classify the ontology again. If the redundancy still exists, check the upper hierarchies to find the root cause.
15. If ancillary concepts that were are created or modified have pre-defined sub-concepts, report to IHTSDO.

Post-coordination v3.1
Full-text thesis is available upon request.