It is also possible to nest expressionsnest
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, one inside the other. Any valid
expression may may be enclosed in a pair of brackets, and included as the value of an attribute in
another expressionanother . For example, the
following expression describes following describes a medication product that has a single dose form, which is both a spray and a suspension:
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373873005 | |
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Pharmaceutical / biologic product|: |
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7946007 |Drug suspension|) |
In the example above, note the use of round brackets (i.e. "( )") to identify a nested expressionnested
, as opposed to braces (i.e. "{ }"), which is used to identify attribute groups.
The following examples show how complex expressions may complex
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may be build up from simple ones, a layer at a time. This
first expression describes first describes a left hip structure:
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24136001| |
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This next expression uses the "left hip" expression above
above to describe a procedure to replace it:
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397956004| |
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Prosthetic arthroplasty of the hip|: |
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Applying a further grouped refinement to grouped
to the above describes a procedure to replace a left hip by inserting a prosthesis. Note that this example mixes an ungrouped qualification and a grouped qualification. Where this is done, the
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of of the expression includes all ungrouped attributes before the grouped ones (
section 7.8.2.4.4.4.2 of the SNOMED CT Technical Implementation Guide [6]see Terminology Services Guide for more details). Please also note that in the previous version of this standard a comma was not permitted between the last ungrouped attribute and the first attribute group – however this comma is now optional to avoid unexpected syntax errors.
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397956004| |
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Prosthetic arthroplasty of the hip|: |
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Procedure site - indirect| |
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{ 363699004|Direct device| = 304120007|Total hip replacement prosthesis|,
260686004|Method| = 425362007|Surgical insertion - action|} |
Finally, the above expression may above
may be included within a contextual wrapper, to describe a procedure that has been performed on a patient to replace a left hip by inserting a prosthesis.
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243796009| |
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Situation with explicit context|: |
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Subject relationship context| |
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=
( 397956004|Prosthetic arthroplasty of the hip|:
405814001|Procedure site - indirect| = (24136001|Hip joint structure|:
272741003|Laterality| = 7771000|Left|)
{ 363699004|Direct device| = 304120007|Total hip replacement prosthesis|,
260686004|Method| = 425362007|Surgical insertion - action|} ) } |