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Data types

The FHIRPath implementation within Pathling supports the following types of literal expressions:

See also: Literals and Using FHIR types in expressions


The Boolean type represents the logical Boolean values true and false.




String literals are surrounded by single-quotes and may use \-escapes to escape quotes and represent Unicode characters:

  • Unicode characters may be escaped using \u followed by four hex digits.
  • Additional escapes are those supported in JSON:
    • \\ (backslash),
    • \/ (slash),
    • \f (form feed - \u000c),
    • \n (newline - \u000a),
    • \r (carriage return - \u000d),
    • \t (tab - \u0009)
    • \`` (backtick)
    • \' (single-quote)

Unicode is supported in both string literals and delimited identifiers.


'test string'
'M\u00fcller' // Includes a Unicode character, evaluates to Müller


The Integer type represents whole numbers.




The Decimal type represents real values.



The implementation of Decimal within Pathling supports a precision of 32 and a scale of 6.


The DateTime literal combines the Date and Time literals and is a subset of ISO 8601. It uses the YYYY-MM-DDThh:mm:ss.ffff±hh:mm format. Z is allowed as a synonym for the zero (+00:00) UTC offset.

Time zone is optional - if it is omitted, the system-configured time zone will be assumed. Seconds and milliseconds precision are supported. Hours precision, minutes precision and partial DateTime values (ending with T) are not supported.


@2014-01-25T14:30:14         // Seconds precision
@2014-01-25T14:30:14+10:00 // Seconds precision with UTC+10 timezone offset
@2014-01-25T14:30:14.559 // Milliseconds precision
@2014-01-25T14:30:14.559Z // Milliseconds precision with UTC timezone offset


The Date type represents date and partial date values, without a time component.

The Date literal is a subset of ISO 8601. It uses the YYYY-MM-DD format, though month and day parts are optional.

Some operations implicitly convert Date values to DateTime values, such as comparison and arithmetic. Note that the Date will be assumed to be in the system-configured time zone in these instances.


@2014-01-25    // Year, month and day
@2014-01 // Year and month only
@2014 // Year only


The Time type represents time-of-day and partial time-of-day values.

The Time literal uses a subset of ISO 8601:

  • A time begins with a @T
  • It uses the Thh:mm:ss.fff format, minutes, seconds and milliseconds are optional


@T07:30:14.350    // Milliseconds precision
@T07:30:14 // Seconds precision
@T14:30:14 // Minutes precision
@T14 // Hours precision


The Quantity type represents quantities with a specified unit, where the value component is defined as a Decimal, and the unit element is represented as a String that is required to be either a valid Unified Code for Units of Measure (UCUM) unit or one of the calendar duration keywords, singular or plural.

The Quantity literal is a number (integer or decimal), followed by a (single-quoted) string representing a valid UCUM unit or calendar duration keyword. If the value literal is an Integer, it will be implicitly converted to a Decimal in the resulting Quantity value.

The calendar duration keywords that are supported are:

  • year / years
  • month / months
  • week / weeks
  • day / days
  • hour / hours
  • minute / minutes
  • second / seconds
  • millisecond / milliseconds


4.5 'mg'      // UCUM Quantity of 4.5 mg
100 '[degF]' // UCUM Quantity of 100 degrees Fahrenheit
6 months // Calendar duration of 6 months
30 days // Calendar duration of 30 days

See: Quantity


A Coding is a representation of a defined concept using a symbol from a defined code system - see Using Codes in resources for more details.

The Coding literal comprises a minimum of system and code, as well as optional version, display, userSelected components:


Not all code systems require the use of a version to unambiguously specify a code - see Versioning Code Systems.

You can also optionally single-quote each of the components within the Coding literal, in cases where certain characters might otherwise confuse the parser.

Examples:|52101004|52101004||Present|problem-list-item|4.0.1|'Problem List Item'|'397956004 |Prosthetic arthroplasty of the hip|: 363704007 |Procedure site| = ( 24136001 |Hip joint structure|: 272741003 |Laterality| = 7771000 |Left| )'

The Coding literal is not within the FHIRPath specification, and is currently unique to the Pathling implementation.

Materializable types

There is a subset of all possible FHIR types that can be "materialized", i.e. used as the result of an aggregation or grouping expression in the aggregate operation, or a column expression within the extract operation. These types are: