How to create and update user defined attribute(UDA) using API

Hi Dear All,

    now I am working on a project and I should create the user defined attribute(UDA) using API in PA module,I have checked the procedure PA_PROJECT_PUB.update_project which in turn call PA_USER_ATTR_PUB.Process_User_Attrs_Data and EGO_USER_ATTRS_DATA_PUB.Process_User_Attrs_Data .As no documents ,I dont know how to create and update the user defined attributes ,any one have the documents or sample code about it ,appreciate it very mush,thanks .

regards .

Frank