Xtemplate is a package of ruby libraries and programs which formats a xml/html document according to a ruby's data structure which consists of hash and array. this idea comes from amrita. so we do not need to explicitly write iterations like for-loop in a template. such iterations are indicated by an expansion data. we can specify a data id in xpath like expression, and reconstruct a given data in a template without writing ruby programs. this mechanism provides interoperablity between a template and a ruby script. we can use xml/yaml documents as an expansion data, since it is automatically converted to a ruby's hash object.