DESIGN
======

Below is a list of design decisions. The justification is to be consulted
whenever a change is considered, to avoid regressions.

### Data type for DB storage of numeric values (`decimal` vs `float`)

* among database engines supported (by Rails), SQLite offers storage of
  `decimal` data type with the lowest precision, equal to the precision of
  `REAL` type (double precision float value, IEEE 754), but in a floating point
  format,
    * decimal types in other database engines offer greater precision, but store
      data in a fixed point format,
* biology-related values differ by several orders of magnitude; storing them in
  fixed point format would only make sense if required precision would be
  greater than that offered by floating point format,
    * even then, fixed point would mean either bigger memory requirements or
      worse precision for numbers close to scale limit,
        * for a fixed point format to use the same 8 bytes of storage as IEEE
          754, precision would need to be limited to 18 digits (4 bytes/9 digits)
          and scale approximately half of that - 9,
    * double precision floating point guarantees 15 digits of precision, which
      is more than enough for all expected use cases,
        * single precision floating point only guarntees 6 digits of precision,
          which is estimated to be too low for some use cases (e.g. storing
          latitude/longitude with a resolution grater than 100m)
* double precision floating point (IEEE 754) is a standard that ensures
  compatibility with all database engines,
    * the same data format is used internally by Ruby as a `Float`; it
      guarantees no conversions between storage and computation,
    * as a standard with hardware implementations ensures both: computing
      efficiency and hardware/3rd party library compatibility as opposed to Ruby
      custom `BigDecimal` type