I'm an absolute FHIR newbie and I'm trying to create a set of StructureDefinitions
and examples for an upcoming medical project.
For this project, we need a very specific resource, which is not supported by any FHIR resource yet. Here's our use case:
We are placing sensors on our Patients while they execute certain exercises (e.g. a leg squat) - we capture the sensor measurements and based on those we assign a pre-calculated bio-mechanical body model to each individual Patient. Those body models are calculated and assigned somewhere else in our system (this process is not relevant here). In a first step, I would like to add all the pre-calculated body models itself to our FHIR dataset as resources - so that I'm able to output all existing body models in our system.
Such a body model consists of an unique identifier, a human readable title and a set of attributes which describe the body model. The crucial part are the attributes - those might vary for each body model and we don't know the set of possible attributes beforehand, hence I need a dynamic format representing key and value of each attribute. If I were to represent this in a simple json structure I'd look as follows:
{
"id": "0",
"title": "SAMPLE_BODY_MODEL",
"attributes": [
{
"key": "ATTRIBUTE_1",
"value": "EXAMPLE_1"
},
{
"key": "ATTRIBUTE_2",
"value": "EXAMPLE_2"
}
]
}
My goal now is to create a StructureDefinition
corresponding to the custom resource I've described above.
Hence I looked up the topic of "custom resources" and found this article on the HL7 site: https://hl7.org/fhir/basic.html - explaining that the Basic
resource should be used for custom resources.
So I went ahead and tried to create a basic resource and extending it:
{
"resourceType": "StructureDefinition",
...
"type": "Basic",
"differential": {
"element": [
{
"id" : "Basic",
"path": "Basic",
"definition": "This element describes a general body model captured during an exercise or a movement, e.g. whilst doing leg squats."
},
{
"id" : "Basic.id",
"path": "Basic.id",
"definition": "ID of the body model"
}
{
"id": "Basic.extension:title",
"path": "Basic.extension",
"sliceName": "definition",
"definition": "Title of the body model",
"min": 0,
"max": "1",
"type": [
{
"code": "string" // I know that's wrong, but I somehow would like to restrict this to a string only
}
]
},
{
"id": "Basic.extension:attributes",
"path": "Basic.extension",
"sliceName": "attributes",
"definition": "Attributes of the body model",
// This is where I'm stuck - how do I define this to be a list of objects consisting of attributes key and value?
}
]
}
}
To sum it all up: How do I create a new StructureDefinition
from a basic resource allowing me to specify a new required attribute named "attributes", which consists of one-to-many elements, which again contain the attributes key and value for the key and value of the body model attributes?
Hope this makes sense - otherwise please feel free to let me know and I'll try to rephrase my question.
Many thanks in advance!
First, for a newbie, you're doing really well :) (And nice job on framing the question well too!)
Your first extension slice has a few issues:
Your second slice will be similar. However, the profile on extension it points to won't constrain extension.value. Instead, it'll slice extension.extension to have two slices, one with a fixed url of "name" and the other with a fixed url of "value". There's an example here of a 2-element complex extension. Your slice names and data types will differ, as will the context, but it should make a good model for you.
If you still have issues, add your revised version to your question and we'll see if we can help further.