Proposed drug model
Sending on behalf of Jim. The document (a Microsoft PowerPoint deck) attached is the deliverable from an IHTSDO outsourced project to propose a SNOMED CT drug model for national use. We would be much obliged if you would review this. There is information in the deck other than the model itself. We would like feedback on the document as a whole, but please focus on the recommended model.
Robert Turnbull
Comments
Thanks for this feedback, Keith.
Couple of requests. Could you please be more specific about how the universal restriction would be an issue for you? Reason I ask is, the universal restriction can ensure that, e.g. “Product containing active ingredients A and B only” is classified as a sibling of “Product containing A only”. Do you want to avoid this classification result, or is it something else? Would you also comment on whether you/we want the (English) syntax that implies that, e.g., Product A has active ingredient A and only A, or that it contains A and possibly but not necessarily some other active ingredient?
The universal restriction is an issue because the description logic ALC, which includes universal and existential qualifications for building complex expressions is known to be PSPACE-complete with respect to satisfiability, and EXPTIME-complete with respect to logical implication...
Although we endorse the idea of moving toward OWL 2 EL profile with concrete domain capabilities, which does not have these PSPACE-complete and EXPTIME-complete computability issues with respect to satisfiability and Logical Implication, moving beyond OWL 2 EL profile with concrete domain is not something we can support, and would not adopt any standard that contained such a requirement.
The proposed classification result:
“Product containing active ingredients A and B only” is classified as a sibling of “Product containing A only”
Is not the way we would want medications organized for decision support capabilities. It is much more important to know what medications may (some restriction) contain an ingredient, and we see little to no value for taxonomic organization by containing only an ingredient (all restriction) using logical qualifications given the computational issues with it. There are other ways to distribute such information, using refsets as one example, where the delivery of such supporting knowledge does not impact the decidability of the T-Box content.
Also, the concept "Product containing active ingredients A and B only" is not what you think it might be. The logical implication is that the ingredient is both A and B at the same time... Which implies existence of a molecule that does not exist (a molecule that is both A and B at the same time). We had a similar issue in the past, where some modelers where attempting to use the all restriction for modeling anatomic locations, and the result was anatomic locations that where both kidneys and lungs at the same time (modeling Goodpasture syndrome).
These issues have been discussed extensively at previous pharmacy meetings on multiple occasions and rejected by the committee. Unfortunately, the author of this proposal chooses to ignore the previous actions, and does not provide adequate background on the reasons for the past rejection. Again, the concern "there are patient safety issues" with using "contains some" semantics over "contains only" semantics is just hyperbole. There are meaningful ways to manage any such patient safety concerns without resorting to a Universal restriction, and then providing a decidability impact on the entire system (and how safe is an undecidable system anyway?).
Over the years, we've had many meetings on the drug model. One thing has been overwhelming consistent: When use of the "all" restriction is proposed, an analysis of the pros and cons, and implementation issues has always led to a conclusion to not use the ALL restriction, and to just use the SOME restriction. I've attended several meetings on this topic.
The assertion that "there are patient safety issues" with using "contains some" semantics over "contains only" semantics is just hyperbole.
Fortunately, the IHTSDO cannot force us to use a model that contains the ALL restriction, and the VA will not adopt the model with this ALL restriction in place.
I'd prefer that the IHTSDO not include the ALL restriction, so we don't have to work on an independent standard, outside of the IHTSDO, but that will be the result, where we will align closely with the Australian Medication Model that does not use the all restriction. I think the IHTSDO is better off implementing a model that contains a foundation that we all can agree to, rather than trying to promote a model that uses the ALL restriction over the objection of several members and organizations.