From XML Schema to JSON Schema: Translation with CHR

ABSTRACT. Despite its rising popularity as data format especially for web services, the software ecosystem around the JavaScript Object Notation (JSON) is not as mature as that of XML, the Extensible Markup Language. For both data formats exists schema languages to specify the structure of instance documents, but there is currently no way to translate already existing XML Schema documents into equivalent JSON Schemas.

In this paper we introduce an implementation of a language translator. It takes an XML Schema Definition (XSD) and creates its equivalent JSON Schema document. Our approach is based on Prolog and Constraint Handling Rules (CHR). By unfolding the XML Schema document into CHR constraints, it is possible to specify the concrete translation rules in a declarative way.