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.
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 equals .
[[+]]: 272741003 |Laterality| = 24028007 |Right| |
If the following values are provided to complete the slot:
182245002 |Entire upper limb| 182281004 |Entire lower limb| 244486005 |Entire eye| 1910005 |Entire ear| |
then the expressions that result from processing the template would be:
182245002 |Entire upper limb|: 272741003 |Laterality| = 24028007 |Right| 182281004 |Entire lower limb|: 272741003 |Laterality| = 24028007 |Right| 244486005 |Entire eye|: 272741003 |Laterality| = 24028007 |Right| 1910005 |Entire ear|: 272741003 |Laterality| = 24028007 |Right| |
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 and a refinement which uses the attribute The value of the attribute may be replaced by any valid value at a future time.
404684003 |Clinical finding|: 363698007 |Finding site| = [[+]] |
If the following value is provided to complete the slot:
53120007 |Upper limb structure| |
then the expression that results from processing the template would be:
404684003 |Clinical finding|: 363698007 |Finding site| = 53120007 |Upper limb structure| |
If, however, the value provided to complete the slot was the expression:
53120007 |Upper limb structure|: 272741003|Laterality| = 7771000 |Left| |
then the result of processing the template would be:
404684003 |Clinical finding|: 363698007 |Finding site| = (53120007 |Upper limb structure|: 272741003|Laterality| = 7771000 |Left|) |
Please note that the template processor must add round brackets around the subexpression to ensure that the resulting expression is syntactically valid.
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 and a refinement whose value equals The attribute name in the expression may be replaced by any valid attribute concept at a future time.
404684003 |Clinical finding|: [[+]] = 80166006 |Streptococcus pyogenes| |
If the following values are provided to complete the slot:
42752001 |Due to| 255234002 |After| |
then the expressions that result from processing the template would be:
404684003 |Clinical finding|: 42752001 |Due to| = 80166006 |Streptococcus pyogenes| 404684003 |Clinical finding|: 255234002 |After| = 80166006 |Streptococcus pyogenes| |