1. A method for implementing a command interface for a software application on a client computer, comprising: receiving a first definition of the command interface from a server computer, the first definition including rules for encoding the command interface on a web browser, the command interface including a command structure for executing commands for a first customer relationship management (CRM) application; performing a conversion of the first definition to a second definition, the second definition including first language for encoding the command interface on a user interface of an email application on the client computer, the first definition including one or more rule attributes that determine whether one or more elements in the first definition are to be configured to a corresponding element in the second definition, the email application on the client computer including support for a second CRM application that is integrated into the email application; determining whether the user interface on the email application on the client computer supports a ribbon interface; when it is determined that the user interface on the email application on the client computer supports the ribbon interface, using the second definition to render the command interface as a ribbon on the email application; when it is determined that the user interface on the email application does not support the ribbon interface, performing a conversion of the second definition to a third definition, the third definition including second language for encoding the command interface as a command bar on the user interface of the email application; and using a command interpreter to process execution of commands selected by a user on the command interface of the email application.