content: type = "object"
  title = "Particle Species"
  description = "Dict of particle quantities."
  propertyNames.pattern = "^\\w*$"
  
  # A particle species requires at least a "position" record
  required = ["position"]
  
  [properties.attributes]
  
  ##################################################
  # First requirement: standard-defined attributes #
  ##################################################
  
  [[properties.attributes.allOf]]
  title = "Particle Species attributes"
  description = "Standard-defined attributes at the Particle Species level."
  # No required attributes
  required = []
  
  [properties.attributes.allOf.properties]
  id."$ref" = "attribute_defs.json#/$defs/int_attribute"
  
  ####################################################
  # Second requirement: General layout of attributes #
  ####################################################
  
  [[properties.attributes.allOf]]
  title = "Attribute layout"
  description = "Custom attributes allowed, no required attributes defined."
  "$ref" = "attributes.json"
  
  [properties.particlePatches]
  title = "Particle Patches"
  "$ref" = "particle_patches.json"
  
  
  [patternProperties."^(?!(attributes|particlePatches)).*"]
  title = "Record"
  "$ref" = "record.json"
  