Basic Customization > User Interface Customization > Customizing HTML Clients Using the Windchill JSP Framework > Adding Validation Logic for Actions and Properties > Structure
  
Structure
All of the classes in the UI Validation Service (except where noted) are defined in the com.ptc.core.ui.validation package.
A Validator developer will not need to interact with all of the classes in this diagram, but many of them are applicable. The various classes will be discussed throughout this document, but to begin with, a developer writing a Validator should always define their Validator class to extend DefaultUIComponentValidator.
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It is also important to note that as requirements evolve, these classes may be updated. To get the latest set of methods and attributes defined in each of the classes see the Windchill Javadoc.