Replacement slots serve as a placeholder for a value that is not known at the time of authoring, but which can be completed at a subsequent time using data recorded elsewhere (such as in an information model or entered into a data entry form). A slot indicates that it may be replaced by a value by including a plus sign ( + ) as the first symbol within the slot. Replacement slots may be used in an expression template wherever a concept, expression or symbol may appear within an expression. 

Focus concept

A replacement slot may be used to delay the selection of a focus concept in an expression. For example, the expression template below uses a slot to indicate that the focus concept in the expression can be replaced with any appropriate SNOMED CT expression. This expression template represents any expression with a single refinement in which the 272741003 | Laterality| equals 24028007 | Right| .

Attribute Value

A replacement slot may also be used to replace an attribute value in an expression. For example, the expression template below represents any expression with a focus concept of  404684003 | Clinical finding|  and a refinement which uses the attribute 363698007 | Finding site| . The value of the 363698007 | Finding site|  attribute may be replaced by any valid value at a future time.

Attribute Name

A replacement slot may also be used to replace an attribute name in an expression. For example, the expression template below represents any expression with a focus concept of  404684003 | Clinical finding|  and a refinement whose value equals 58718002 | Rheumatic fever| The attribute name in the expression may be replaced by any valid attribute concept at a future time.