Action-based vs. result-based properties of Observations

Introduction

During the disambiguation of negationInd we dealt with the duality between action and statement about the action that is inherent in every HL7v3 Act. It was then noted that for Observations, we not only collapse action and statement into one object, but also the action and its result. It became clear that for some attributes (most notably negationInd again), but also for associations with other classes, it is necessary to clarify whether it relates to the action itself or to the result.

Background

In MnM it was decided to propose a new attribute of Observation, value_negationInd, that would specifically negate the result of the Observation, and not the Observation as a whole (i.e., it wouldn't say that the Observation didn't take place, but that it's result was NOT X).

We have the same issue with some associated classes, most notably Severity, that is often associated with Observations. The severity is not a statement about the observation itself, but about its value/result. It doesn´t say that a diagnostic judgment was an arduous task, but that e.g. the diabetes that was diagnosed was of a severe nature.

Dicussion

An observation and its result are inextricably linked. But we will have to talk about the different ways that observation is used and abused. Once that is cleared up (realistically clearing this up is as nice to have as it is impossible), we *MIGHT* say that there are two stages in an Observation:

- an action to find an answer
- the answer found through the action.

The action defines what you can find. If you read a meter you find numbers. If you ask a yes-no-question you find yes or no. If you ask an open question you find free text. If you look at this text finding features you find features in the answer. If you look for shapes under a microscope you find shapes.

There is no statement of a result that can stand without also saying what was done to get that result. Do heights not exist without people measuring them? They may or may not, we don't need the scholastic dispute, but what matters is that if you speak about height, you have to say what height and at least roughly how it was measured. You cannot even think of an abstract height without considering how you would measure it. Metrology tells us that measured properties are to be defined in an operational manner (operational is just a synonym for actionable, i.e., no property without the possibility of a measurement act.)

Alternative solutions

1) We just accept that for every ActRelationship type we need to make it clear in its definition whether it refers to the action itself or to the result of the Observation. For type codes that can 'go either way' (like subject) this should be fixed per R-MIM.

2) We specialize existing type codes to be able to choose the one that matches it purpose.

3) We add an extra attribute to ActRelationship that can be set to specify the distinction.

This is clearly not different from something like context conduction, which is also usually clear from context, but has a specific attribute to allow (or even enforce) setting it explicitly. I don't see why we should treat it any differently...

In the case of Severity though, I actually feel we would still benefit from a separate attribute on the Observation, just like a new attribute was proposed to negate the value. Again, I don't see why we should treat these any differently...

By the way, there is still the alternative option

4) We separate the action and the result into two separate classes, so that any association explicitly refers to either one with no extra effort. It's radical, but it's also neat.