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Release data structures for the MAP are compliant with SNOMED CT Release Format 2 (RF2) datasets as defined in the SNOMED CT Release File Specification. SNOMED CT Release Files relevant to the MAP structures and definitions important to MAP deliverables identified below include:
Reference Set (Refset): which is defined as
a standard format for maintaining and distributing a set of references to SNOMED CT components.
Map member: a single Refset MAP data record which assembles knowledge-based data required to validate the link between a single SNOMED CT concept and at most one ICD-10 classification code. The Map member includes a link to the source SNOMED CT concept identifier, a mapGroup integer, a mapPriority integer, a mapCategoryId status concept reference, a mapRule, mapAdvice, and link to at most one mapTarget ICD-10 classification code.
mapGroup: an integer assigned to each set of Map members which are coordinated to specify one target ICD-10 code for the map, or the null map if the source concept does not require an additional ICD-10 code for proper classification. Each mapGroup collates and orders the rules, which are sequentially evaluated to yield at most a single target code. The first mapGroup designates the set of records used to specify the first (primary) target code. The second mapGroup identifies the set of data records for the second target code. These are repeated as required to specify a complete set of mapping target codes.
mapPriority: an integer which designates the sequence of run-time Map member processing within each mapGroup. Each data record may include a rule which is designed to be processed in order to provide knowledge-based mapping. Only the first Map member meeting the run-time criteria is taken for the target code within the mapGroup data records.
mapCategoryId: a SNOMED CT foundation metadata concept identifier which indicates the process state for run-time use including the editorial status of the Map member:
There are additional Map Categories that identify editorial process states but are published as a single Map member for the source concept for completeness, auditability and transparency of the MAP:
mapRule: A machine-processable truth statement created to evaluate to "true" or "false" at run-time, which determines whether the Map member should be validated as the correct link to the associated map target for the mapGroup being evaluated.
Formatting of the mapRule is specified in Augmented Bacchus Naur Form (ABNF) in Appendix A but generally is one of three forms:
IFA Concept.id [= VALUE]: a mapRule which evaluates for the existence of one or more SNOMED CT concept instances including their descendant concepts, or an observable and value found in the patient record. The concept is designated by the SNOMED CT Identifier for a clinical finding or observable entity and the SNOMED CT fully specified name. In the case of rules for age at onset of clinical finding or current chronological age, it may include a range of allowable "VALUES". If such an instance is found in the patient record at the time of rule evaluation, the rule is evaluated as "true" and the associated map target is selected for that mapGroup. Otherwise the rule evaluates as "false" and the run-time evaluation proceeds to the next Map member within the mapGroup. The mapAdvice for the record will include a readable statement relating the rule and map target.
mapAdvice : human-readable textual advice that a software vendor may employ to inform the clinician user or the classification expert during a semi-automated mapping session. The mapAdvice has three components separated by vertical bar ("|"):