Parser behaviour

The parser permits non-SGF content to appear before the beginning and after the end of the game. It identifies the start of SGF content by looking for (; (with possible whitespace between the two characters).

The parser accepts at most 64 letters in PropIdents (there is no formal limit in the specification, but no standard property has more than 2; strings as long as 9 letters have been found in the wild).

The parser doesn’t perform any checks on property values. In particular, it allows multiple values to be present for any property.

The parser doesn’t, in general, attempt to ‘fix’ ill-formed SGF content. As an exception, if a PropIdent appears more than once in a node it is converted to a single property with multiple values.

The parser doesn’t permit lower-case letters in PropIdents (these are allowed in some ancient SGF variants).