The Object-Role Modeling (ORM) standard version 2, associated schemas and generation tools, and a reference implementation in the form of the Natural Object-Role Modeling Architect for Visual Studio (NORMA) product.
XMLminus is a utility for saving and loading data in a format based on XML, but slightly modified for simplicity. XMLminus is not suited for writing documents, but is excellent for data serialization. XMLminus is written in modern C++.
ooRuleML library is the object oriented C# implementation of the Rule Markup Language (RuleML).