To be a 'compliant' parser, you generally have to implement the whole spec. The bigger the spec, the more complicated the parser. The less stuff from the spec

To be a 'compliant' parser, you generally have to implement the whole spec. The bigger the spec, the more complicated the parser. The less stuff from the spec you use, the less gets tested. What's silly is picking a 'standard' and thinking because you only use a little bit, you're safe.