At this level, the terminology server requires all submitted expressions to already be in valid classifiable form. This form is a syntactically valid and concept model compliant representation expression that can be directly used as input to the classifier, enabling expressions to be classified together with other SNOMED CT content.
For more details on the Machine Readable Concept Model, please see http://snomed.org/mrcm.
Implementation Advice
To enable postcoordination at Level 0, it is important that the system used to create the expressions supports any transformation needed to represent the expressions in their classifiable form. This may be enabled using one of the following techniques:
These techniques will support the creation of expressions that fully comply with the concept model rules and avoid some of the common mistakes created. For example using attributes that are incorrect for the domain or incorrectly grouped.
Incorrect Attributes
Consider the situation where the following expression is created to represent the meaning of a "Disorder of left lung":
At level 0, this expression would not be accepted by the terminology server, because the MRCM only permits those concepts that are both within the
<<
91723000 |Anatomical structure (body structure)|
domain and also listed in the
723264001 |Lateralizable body structure reference set|
to be qualified using
272741003 |Laterality (attribute)|
. The focus concept of the expression is neither.
As a result of this rule, the action required to make the expression classifiable, is to add a nested expression where the laterality is applied to the value of the 363698007 | Finding site (attribute)| attribute that is part of the NNF for the same focus concept, 19829001 | Disorder of lung (disorder)| , as follows:
Incorrectly Grouped Attributes
Consider the situation where the following expression is created to express the meaning of a "Procedure on left lung":
At level 0, this expression would not be accepted by the terminology server, because
363704007
|
Procedure site (attribute)|
is specified as being 'grouped', which requires a role group to be explicitly stated. As a result of this rule, the action required to make the expression classifiable, is to place the attribute in a group, as follows:
Examples
Terminology servers at level 0 will reject any expressions not conforming to the classifiable form.
Table 5.3.1-1 provides examples of a set of expressions with an indication of their acceptability and potential issues at level 0.
Expression | Classifiable | Issue |
|---|---|---|
No | Attribute 363698007 | Finding site| should be in a group | |
Yes | ||
Yes | Although this expression complies with the concept model rules, the expression will not classify as probably desired, as a subtype of 188060000 |Malignant melanoma of shoulder (disorder)| The reason for this is that the stated group does not include the required attribute: 116676008 |Associated morphology (attribute)| = 1162635006 |Malignant melanoma (morphologic abnormality)| | |
No | Attribute 363698007 | Finding site| should be in a group | |
Yes | ||
No | Attribute 272741003 | Laterality| does not apply to the domain | Malignant melanoma of shoulder| |
Table 5.3.1-1: Example expressions with an indication of their acceptability and potential issues at level 0
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