Dictionary Syntax¶
The Physical Constants Dictionary (PCD) is codified in YAML 1.2.
The content of such YAML file must comply with the current syntax rules:
Main Structure¶
A PCD is a YAML node of kind mappings, i.e. an unordered set of key: value node pairs, with the unique key name physical_constants_dictionary.
Top-Level Fields¶
The value associated to the physical_constants_dictionary key consists of the following YAML mapping nodes:
version_number (optional)¶
The dictionary version, as in the standard GNU scheme: major.minor.revision
institution (optional)¶
The name of the institution responsible for the dictionary
description (optional)¶
A short description of the dictionary file
contact (optional)¶
The email address of the designed POC for this file
set (mandatory)¶
Internally consistent physical constants sets are included as YAML block sequences of mappings. A physical constant set is codified as a YAML mapping node, with the set name as the main key. Each set must begin with a hyphen (-), separated by space from the set name (key).
Physical Constants Sets¶
The value associated to a set key includes the following mapping nodes:
description (mandatory)¶
A brief description of the constants set
citation (mandatory)¶
Literature references associated with the set
entries¶
This node includes the actual dictionary entries for each physical constant included in the set. Entries are also organized as block sequences of mapping nodes, and must begin with a hyphen (-).
Physical Constant Entry Format¶
A physical constant entry can be defined as shown in the example below:
- name: standard_acceleration_of_gravity
value: 9.80665
units: m s-2
prec: double
type: strict
uncertainty: exact
description: |
Nominal acceleration of an object in a vacuum at sea level at a
geodetic latitude of 45 degrees.
Entry Field Definitions¶
The name of each key and its associated value are listed below:
name¶
Physical constant's standard name
value¶
Physical constant's numerical value
units¶
Physical constant's units
prec¶
single (4 bytes) or double (8 bytes) indicate the parameter's kind in Fortran
uncertainty (optional)¶
The constant's absolute uncertainty (a number, or exact)
relative_uncertainty (optional)¶
The constant's relative uncertainty (a number, or exact)
description¶
A detailed description of the physical constant, with additional references if necessary.