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   1 # ♓️🪡 सूत्र ∷ X·S·D
   2
   3 ♓️🪡 सूत्र ∷ X·S·D provides an implementation of the
   4 [X·M·L Schema Definition Language][XSD-1], including the
   5 [X·M·L Schema Definition Datatypes][XSD-2], for Ecmascript.
   6
   7 ## Notes
   8
   9 ### Typechecking
  10
  11 All of the functions provided by `./functions.js` will throw an error
  12 if they are given arguments which do not match the expectations
  13 established by the X·S·D spec. No type coersion occurs.
  14
  15 ### Efficiency
  16
  17 ♓️🪡 सूत्र ∷ X·S·D emphasizes algorithm correctness and takes a somewhat
  18 extreme stance with regards to spec adherence. This means that the
  19 algorithms used may be somewhat slow, although native platform features
  20 will be leveraged when possible.
  21
  22 ### Numeric values
  23
  24 ♓️🪡 सूत्र ∷ X·S·D treats all numeric values as native Ecmascript
  25 numbers. This may lead to rounding errors for decimals and extreme
  26 values.
  27
  28 This behaviour may change in the future; see
  29 <https://github.com/tc39/proposal-decimal> for progress on getting a
  30 more precise decimal type into Ecmascript.
  31
  32 ### Positive and Negative Zero
  33
  34 X·S·D only formally distinguishes positive and negative zero for floats
  35 and doubles, but it allows them to be represented lexically in all
  36 other signed numeric types. ♓️🪡 सूत्र ∷ X·S·D silently coerces negative
  37 zero to positive zero for numeric datatypes in which it is not an
  38 explicit part of the value space, as well as for numeric components of
  39 other datatypes (e·g durations).
  40
  41 ### Date∕times and Durations
  42
  43 ♓️🪡 सूत्र ∷ X·S·D does not provide actual classes for X·S·D
  44 date/timeSevenPropertyModel values or durations, treatings both as
  45 simple objects. This approach was taken to maximize compatibility with
  46 other modules. Formally :—
  47
  48 1. A duration is any object for which getting the `months` property
  49    returns an integer, getting the `seconds` property returns a finite
  50    number, and these two values have the same sign. (Positive and
  51    negative zero are treated as having the same sign for this
  52    comparison.)
  53
  54    Note that `months` and `seconds` **must not** be undefined.
  55
  56 2. A date/timeSevenPropertyModel value is any object for which getting
  57    the `year`, `month`, `day`, `hour`, `minute`, `second`, and
  58    `timezoneOffset` properties returns values within the bounds
  59    specified in the X·S·D specification. Absent values can be
  60    represented with undefined, and need not actually be defined on the
  61    object).
  62
  63 Functions which return durations or date/timeSevenPropertyModel values
  64 will always return a plain, extensible object which :—
  65
  66 - Inherits from `%ObjectPrototype%`,
  67 - Has all of the applicable properties defined as enumerable,
  68   configurable, writable own data properties (absent properties will be
  69   defined with a value of undefined), and
  70 - Has no other own properties.
  71
  72 [XSD-1]: <https://www.w3.org/TR/xmlschema11-1/>
  73 [XSD-2]: <https://www.w3.org/TR/xmlschema11-2/>