ISO/IEC 18025:2014 provides mechanisms to specify unambiguously objects used to model environmental concepts. To accomplish this, a collection of nine EDCS dictionaries of environmental concepts are specified: classifications: specify the type of environmental objects; attributes: specify the state of environmental objects; attribute value characteristics: specify information concerning the values of attributes; attribute enumerants: specify the allowable values for the state of an enumerated attribute; units: specify quantitative measures of the state of some environmental objects; unit scales: allow a wide range of numerical values to be stated; unit equivalence classes: specify sets of units that are mutually comparable; organizational schemas: useful for locating classifications and attributes sharing a common context; and groups: into which concepts sharing a common context are collected. A functional interface is also specified. As denoting and encoding a concept requires a standard way of identifying the concept, ISO/IEC 18025:2014 specifies labels and codes in the dictionaries.
