Metadata Expressions

The metadata expressions editor enables you to define what Simplifier should display as Title, Description, UrlKey, Workflow or FilePath for your resources. To start editing the metadata expressions of your project, select Settings and click on Metadata Expressions.

When editing the metadata expressions you will have access to the default expressions used by Simplifier. If your FhirPath expressions are missing, are not correct or the value extracted is empty, Simplifier will fall back to the default expressions. If a default expression is not able to provide a value, a generic text based on the resource type will be used. Workflow and FilePath don’t have a default expression. For FilePath in this case, if the extracted value is empty or missing, the fallback will be the original/generated filepath of the uploaded file.

As a convention, you must specify the resource type followed by the property (Title, Description, UrlKey, Workflow or FilePath) with a semicolon and the FhirPath expression based on which we extract the value.


For more information on how to use FhirPath, visit the following link to the FhirPath specification:

Title and Description

Using Title and Description in the expressions, you can influence how they are displayed in search results and on the resource page.


Patient.Title: identifier

Note that in this example, identifier and are both collections that could contain more than one item. By default Simplifier only takes the first item of a collection. We built a custom FhirPath function to concatenate multiple items called glue(). The items are separated by the argument that is passed to this function.


Patient.Description:', ')

The description of the Patient resource will now show all family names of the patient, separated by a comma. It is also possible to take only the first name of the patient by adding [0] to the element. Another possibility is to merge collections from different elements by using the | character. So, to show the first given name and the first family name separated by a space, you would use:

Patient.Description: (name[0].given[0] | name[0].family).glue(' ')

Note that the | character usually functions as an OR operator, as Simplifier will only select the first item in a collection. For example, say you want to show the name of an organization, but if name is empty you want to show the (first) identifier. You could use the following expression to do so:

Organization.Title: name | identifier[0].value

In some cases, you may want to select the first item of a collection yourself. For example, when you want to add additional text as well. In this situation, you could also use the first() function that is available in FhirPath.


PractitionerRole.Title: 'Role(s) of ' + (practitioner.display | practitioner.reference).first()

This example will show the value in the display element in the Reference to practitioner, if available. If not available, it will show the value in the reference element. If none of these values are available, Simplifier will fall back to the default value Example of a PractitionerRole that is defined in the core code.

There is a difference between using the + operator and the & operator to concatenate values. When the + operator is used and one of the values is empty, the complete result will be empty. When the & operator is used, it doesn’t matter if any of the values are empty. The remaining values will still be concatenated. So, if we would have used the & operator instead of the + operator in the example above, and both practitioner.display and practitioner.reference are empty, Simplifier will show the Title of the PractitionerRole resource as follows: Role(s) of, which is not what we wanted.


Special attention must be paid to the FilePath property. Since the filepath of the file is used for matching files in Simplifier, uniqueness is necessary. The extracted value for FilePath using the metadata expression must be unique within the project. Otherwise, a default fallback will be used or a new filepath will be generated.


In case the project is linked to a Github repository and there is a FhirPath expression specified for FilePath in the metadata expressions screen, the resulting value must match the filepath of the file in Github. If the filepath doesn’t match, the link is broken and the file will not be synced anymore.


The Workflow property is populated using a FhirPath expression for extracting a value from the extension of the resource. The extracted workflow key will be used to identify the corresponding workflow status from the custom workflow selected within the project in Simplifier.


StructureDefinition.Workflow: extension(


When a property (Title, Description, UrlKey, Workflow or FilePath) should use the same FhirPath expression for all resource types, the generic Resource can be used.


Resource.FilePath: extension(

The editor supports comments as well. Comments can be entered by using the # or // characters.


#Resource examples
Observation.Title: code.text
Profile.Description: <expression for your description>
StructureDefinition.FilePath: <expression for filepath>