A programmable object model includes a plurality of object-oriented message calls for application programming interfaces allowing a user to programmatically access the schema validation model of an application by sending message calls and required parameters to the schema validation model to customize or otherwise modify the operation of the schema validation model as desired by the user. Once the user has access to the schema validation model of an application, the user may attach Extensible Markup Language (XML) schema files to a document and control definitions, grammatical rules, and other settings dictated by the attached XML schema file. The user also is allowed to customize the application's native schema validation functionality with user-defined rules and error text. The XML schema validation model of an application may be accessed from a user-created program written according to a variety of different languages such as C, C++, C#, and Visual Basic.