This section explains the correct order of operation for unary operators, binary operators, filters and supplements.

Unary Operators

Unary operators (e.g. descendantOf, descendantOrSelfOf, ancestorOf, ancestorOrSelfOf, memberOf) are applied from inside to out (i.e. from right to left). For example, when the following expression constraint is processed, the memberOf operator is applied first to the Example problem list concepts reference set, and then the descendants of the referenced components are determined. 

	< ^ 700043003 |Example problem list concepts reference set|

Binary Operators

Whenever potential ambiguity in binary operator precedence may occur, round brackets must be used to clearly disambiguate the order in which these operators are applied. For example, the following expression constraint is not valid:

...

Please note that unary operators are always applied before binary operators.

Filter Constraints

Filter constraints (e.g. concept, description, or member filters) apply only to the sub-expression constraint part that is directly to the left of the filter.

For example, the following expression constraint will apply the term filter to only the descendants or self of 

<  404684003 |Clinical finding| :
         363698007 |Finding site|  = <<  39057004 |Pulmonary valve structure| , 
         116676008 |Associated morphology|  = <<  415582006 |Stenosis| {{ term = "insufficiency" }}

To apply a filter to a sub-expression constraint, which includes a refinement or binary operators, the subexpression must be enclosed in brackets. For example, the following expression constraint will find all the descendants of clinical finding, with a finding site that is a descendant or self of 

(<  404684003 |Clinical finding| :
         363698007 |Finding site|  = <<  39057004 |Pulmonary valve structure| , 
         116676008 |Associated morphology|  = <<  415582006 |Stenosis|) {{ term = "insufficiency" }}

History Supplements

History supplements are applied only to the sub-expression constraint part that is directly to its left, after any filter constraints on this sub-expression constraint part have been applied.

For example, the following expression constraint will match all concepts that are both an active member of the 

	^ 734139008 | Anatomy structure and part association reference set| 
		AND ^ 734138000 |Anatomy structure and entire association reference set|  
			{{ + HISTORY (900000000000527005 |SAME AS association reference set|) }}

To apply the history supplement to the entire sub-expression constraint above, the sub-expression constraint must be enclosed in round brackets. For example, the following expression constraint will match concepts that are both members of the 

	( ^ 734139008 | Anatomy structure and part association reference set| 
		AND ^ 734138000 |Anatomy structure and entire association reference set| )
			{{ + HISTORY (900000000000527005 |SAME AS association reference set|) }}