A field that is a combination of other meaningful data fields. Each portion is called a component. The specific components of CM fields are defined within the field descriptions. Certain other composites have been separately identified and are described below. The CM data type is maintained strictly for backward compatibility and may not be used for the definition of new fields. Wherever a component of an HL7 field is itself an HL7 data type which contains components, its delimiters are demoted by one. Thus a component designated as a CE data type should be encoded as <identifier & text & name of coding system> (see Section 2.8.3, "CE - coded element"). Note that since HL7 delimiters are not recursive, an HL7 data type containing components cannot be a sub-component. When this level of detail is needed, each component of the HL7 data type can be encoded as a separate subcomponent. For an example of this, see the encoding of the filler order number in the order sequencing component of the Timing/Quantity data type.