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where [sctid] is the concept id that identifies the given SNOMED CT edition (based on the identifier of the most dependent module), and "YYYYMMDD" is the date of release. Examples of sctids that identfy identify a specific edition are shown in the table below:
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32506021000036107
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20611000087101
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4.2.1.0.3 Display
TODO Advice on the following (requested from LP in comments): What is the guidance when we need to refer to the language refset? what is the guidance when and if we want to define a display term for an expression? What if another term than the preferred term is selected for the display term?
Any number of terms in additional languages and dialects can be specified for a given code in the "Designation" field (eg ValueSet.compose.include.concept.designation ) where the particular language refset to be referred to can be mapped from the language code field "Language"(eg ValueSet.compose.include.concept.designation.language) and the type of the term (ie FSN, Synonym, Definition) is held in the "Use" field ValueSet.compose.include.concept.designation.use.
4.2.1.0.4 Copyright and Licenses 
Note that many implementations are in the habit of simply using the date of release in the form YYYYMMDD (e.g. "20140531"), and assuming that the edition is known. However this is not always safe, so implementations that populate the version element must use the URI form.
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.
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This specification includes content from SNOMED Clinical Terms® (SNOMED CT®) which is copyright of the International Health Terminology Standards Development Organisation (IHTSDO). Implementers of these specifications must have the appropriate SNOMED CT Affiliate license - for more information contact http://www.snomed.org/snomed-ct/get-snomed-ct 
or info@snomed.org.
4.2.1.0.
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5 RDF
The SNOMED International URI specifications use the namespace http://snomed.info/sct for the code system, and the URI http://snomed.info/id for the individual concepts in the code system. This means that when a SNOMED CT concept is converted from the system::code pair, where the system is http://snomed.info/sct, to the RDF ontological form, the representation is http://snomed.info/id/[concept-id]. Expressions are represented using the URI pattern http://snomed.info/scg/[expression]. Expressions represented in this way SHALL not contain whitespace, terms, or comments.
4.2.1.0.
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6 SNOMED CT Properties
In addition to the standard properties, the following properties are defined for SNOMED CT:
| inactive | boolean | Whether the code is active or not (defaults to false). This is derived from the active column in the Concept file of the RF2 Distribution (by inverting the value) |
| sufficientlyDefined | boolean | True if the description logic definition of the concept includes sufficient conditions. This is derived from the definitionStatusId value in the Concept file of the RF2 distribution (i.e. If 900000000000073002 |Sufficiently defined concept definition status| then true). |
| moduleId | code | The SNOMED CT concept id of the module that the concept belongs to. |
| normalForm | string | Generated Normal form expression for the provided code or expression, with terms |
| normalFormTerse | string | Generated Normal form expression for the provided code or expression, conceptIds only |
| . |
In addition, any SNOMED CT relationships where the relationship type is subsumed by 410662002 |Concept model attribute| automatically become properties. For example, the laterality property is represented using the conceptId for 410662002 |Laterality|:
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Note that when a $lookup operation is performed on a SNOMED CT concept, servers SHALL return the full URI for the edition and version being used (see above) in the version property. Other properties are at the discretion of the server and the client.
4.2.1.0.
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7 SNOMED CT Filters
This section documents the property filters that can be used with the SNOMED CT code system in value set composition statements.
For implementer convenience, some of the property filters are documented in terms of the SNOMED CT Expression Constraint Language, but this does not imply that its use is required.
4.2.1.0.
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7.1 By Subsumption
| Description | Select a set of concepts based on subsumption testing |
| Property Name | concept |
| Operations Allowed | is-a |
| Values Allowed | [concept id] |
| Comments | Includes all concept ids that have a transitive is-a relationship with the concept Id provided as the value (including the concept itself) |
| Example | Administration Methods |
<< [concept] (Long syntax: descendantOrSelfOf [concept]) |
4.2.1.0.
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7.2 By Reference Set
| Description | Select a set of concepts based on their membership of a SNOMED CT reference set |
| Property Name | concept |
| Operations Allowed | in |
| Values Allowed | [concept id] |
| Comments | Includes all concept ids that are active members of the reference set identified by the concept Id provided as the value |
^ [concept] (Long syntax: memberOf [concept]) |
4.2.1.0.
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7.3 By SNOMED Expression Constraint
| Description | Select a set of concepts based on a formal expression constraint |
| Property Name | constraint |
| Operations Allowed | = |
| Values Allowed | [expression constraint] |
| Comments | The result of the filter is the result of executing the given SNOMED CT Expression Constraint "compose": {
"include": [
{
"system": "http://snomed.info/sct",
"filter": [
{
"property": "constraint",
"op": "=",
"value": "<< 30506011000036107 |Australian product|: 700000101000036108 |hasTP| = 17311000168105 |Panadol|"
}
]
}
]
}
|
4.2.1.0.
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7.4 By whether postcoordination is allowed
| Description | Specify whether postcoordination is allowed or not |
| Property Name | expressions |
| Operations Allowed | = |
| Values Allowed | true or false |
| Comments | Expressions, if allowed, are subject to the same rules as precoordinated concepts. (Note: simple reference sets do not include expressions). |
| Example | Administration Methods |
n/a |
4.2.1.0.
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8 Implicit Value Sets
Implicit value sets are those whose specification can be predicted based on the grammar of the underlying code system, and the known structure of the URL that identifies them. SNOMED CT has two common sets of implicit value sets defined: By Subsumption, and By Reference Set. These implicit value sets do not use complex queries. This allows a single URL to serve as a value set definition that defines a value set, and can serve as the basis for the $expansion operation.
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<ValueSet xmlns="http://hl7.org/fhir">
<text>
<status value="generated"/>
<div xmlns="http://www.w3.org/1999/xhtml">
[Some HTML that describes this value set as all concepts in the reference set identified by conceptid]
</div>
</text>
<url value="[edition/version]?fhir_vs=refset/[sctid]"/>
<version value="[edition/version]"/>
<name value="SNOMED CT Reference Set [conceptid]"/>
<description value="All SNOMED CT concepts in the reference set [concept id or preferred description]"/>
<copyright value="This value set includes content from SNOMED CT, which is copyright © 2002+ International Health Terminology Standards Development Organisation (IHTSDO), and distributed by agreement between IHTSDO and HL7. Implementer use of SNOMED CT is not covered by this agreement"/>
<status value="active"/>
<compose>
<include>
<system value="http://snomed.info/sct"/>
<filter>
<property value="concept"/>
<op value="in"/>
<value value="[conceptid]"/>
</filter>
</include>
</compose>
</ValueSet>4.2.1.0.
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9 Implicit Concept Maps
Implicit concept maps are those whose specification can be predicted based on the grammar and/or content of the underlying code system, and the known structure of the URL that identifies them. This allows a single URL to serve as a concept map definition that defines a mapping between two sets of concepts, and which can serve as the basis for the $translate operation. SNOMED CT has two common sets of implicit concept maps defined:
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We've added a new section for Expressions. Bringing other text on the page into line with SNOMED International's definition of what constitutes valid SNOMED CT compositional grammer, we've removed advice about including or not including text definitions - both are considered equally valid, although there may be an argument for including the orginal text selected by the end user.
SNOMED CT Properties
The following property has been removed since "NormalForm" covers this case in that SNOMED CT Expressions are considered valid with our without terms. These can be added or stripped out as required, locally and programmatically, for display purposes.
| normalFormTerse | string | Generated Normal form expression for the provided code or expression, conceptIds only |