As a set of standards, Medical Markup Language (MML) has been developed over the last 8 years to allow the exchange of medical data between different medical information providers MML version 2.21 was characterized by XML as metalanguage and was announced in 1999, at which time full-scale implementation tests were carried out; subsequently, various information and functional inadequacies were discovered in this version. MML was therefore updated to version 2.3 in 2001. At present, MML contains 12 MML modules including the new referral, test result, and report modules. In version 2.3, the group ID element was added; the access right definition and health insurance module were amended.