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AQL syntax supports parameterization. AQL parameters are used to indicate a criteria, which will be substituted with real criteria value at run time. Supporting parameterization is one of the mechanism used to realise sharing AQL statements within a system or cross system boundaries.
The parameters can be EHR specific (such as the parameter of EHR identifier or EHR creation date time), archetype specific (such as parameter of an archetype identifier, or archetype constraints), or template specific (such as parameter of a template identifier or template constraints).
When parameters are needed
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There is no specific guidelines on how to resolve query parameters. Generally speaking, a parameter name is used as a key (or a key is associated with a parameter within a query contextname) and the key needs to be unique within the boundary where the parameters are resolved. The EHR system or application needs to have the API functions to get the real value with a given parameter name or key.
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