Principles

[niquola]

Principles we follow while designing spec:

• Queries written against the spec should be portable between institutions
• Queries written against the spec should be translatable between database engines that have JSON support (i.e., avoiding features that are not widely implemented)
• Schemas and transformations should depend as little as possible on specific FHIR versions and profiles
• It should be possible to run transformations on raw data prior to loading it into a database (ETL) or within a database using SQL (ELT)
• Use $ prefix for all calculated elements to avoid clash with FHIR elements

[gotdan]

Per #45 the last bullet should be something supported by most DBs like sof_