FHIRPath
FHIRPath is a path-based navigation and extraction language, similar to XPath. It is designed to operate on hierarchical data models, enabling operations such as traversal, selection, and filtering of data. FHIRPath is particularly suited to the healthcare domain, where it is used extensively with HL7 Fast Healthcare Interoperability Resources (FHIR). The language's design was heavily influenced by the need to navigate paths, select specific data points, and formulate invariants within FHIR data models.
Fhircraft provides a fully compliant FHIRPath engine that adheres to the FHIRPath Normative Release v2.0.0 (ANSI/HL7 NMN R1-2020). This engine allows users to parse and evaluate FHIRPath expressions against FHIR data structures.
Basics
FHIRPath expressions
The Fhircraft FHIRPath engine can be accessed through the fhircraft.fhir.path module, where an initialized instance is available as fhirpath. This engine provides a parse method, which is used to convert string-based FHIRPath expressions into their corresponding Python representations.
The expression object represents the parsed FHIRPath expression in Python, which can then be used to evaluate the expression against FHIR-compliant Python objects.
Info
For a comprehensive guide on constructing FHIRPath expressions, refer to the official FHIRPath documentation.
FHIRPath expressions operate on collections, meaning that the result of every expression is a collection—even when the expression yields a single element. This design simplifies path specification by abstracting away the need to consider the cardinality of individual elements, making it particularly well-suited for traversing graph-like structures. To evaluate a parsed expression and retrieve the value(s) from a FHIR object, you can use the get_value method.
This method will execute the FHIRPath expression against the provided FHIR object and return the corresponding collection of values.
Advanced Usage
Warning
Under construction, TBA