The figures in this section illustrate some terms used to describe different parts of an in the discussion of , the guidance on and on .

Focus concepts and refinements
As illustrated by , an consists of one or more conceptIds plus optional . The may include any number of attributes. are expressed as name-value pairs and may apply independently or as part of a group.

The name part of the  is a conceptId that refers to a that names the characteristic that is refined by this attribute. The value part of the  is an . In simple cases, this is just a conceptId referring to a that represents the appropriate value for this attribute. However, it may also be a nested as shown in .

 illustrates the potential for nesting of  and the naming conventions applied in this guide to distinguish different parts of an at different levels. The top level of an  is referred to as the "focus expression". It consists of a set of one or more  and a . The values of the attributes in the   are a "nested expression" that consist of one or more "value concepts" optionally refined by a nested . may be nested recursively so there may be further levels of "nested expressions" with "nested refinement". If it is necessary to distinguish the level of nesting, the following naming convention is applied.

Expression Nesting 

Level number


level 0


level 1



Annested inside a level ( N - 1)


Illustration of the names used to refer to parts of a nested expression
The general pattern shown in  applies to all whether or not they include  information.  illustrates the specific features of an that includes a representation of .

The "focus expression" of a context containing is the  and may include a "context refinement" consisting of a set of context attributes:

In a normalized context , all context attributes are grouped. Each group in a normalized contains a complete set of four context attributes [1 .

The value of the or is a "nested expression" which is referred to as the "clinical kernel".

During some stages of processing, the "clinical kernel" is separated from the "nested expression". When separated from its context the "clinical kernel" is the "focus expression" of a context-free .


Illustration of the names used to refer to parts of an expression that represent context