include all forms of non volatile memory media and memory devices including by way of example semiconductor memory devices e g eprom erasable programmable read only memory eeprom electrically erasable programmable read only memory and flash memory devices magnetic disks e g internal hard disks or removable disks magneto optical disks and cd rom and dvd rom disks the processor and the memory can be supplemented by or incorporated in special purpose logic circuitry to provide for interaction with a user embodiments of the subject matter described in this specification can be implemented on a computer having a display device e g a crt cathode ray tube or lcd liquid crystal display monitor for displaying information to the user and a keyboard and a pointing device e g a mouse or a trackball by which the user can provide input to the computer other kinds of devices can be used to provide for interaction with a user as well for example feedback provided to the user can be any form of sensory feedback e g visual feedback auditory feedback or tactile feedback and input from the user can be received in any form including acoustic speech or tactile input the computing system can include clients and servers a client and server are generally remote from each other and typically interact through a communication network the relationship of client and server arises by virtue of computer programs running on the respective computers and having a client server relationship to each other embodiments of the subject matter described in this specification can be implemented in a computing system that includes a back end component e g as a data server or that includes a middleware component e g an application server or that includes a front end component e g.