Provided is a method, system, program, and data structure for applying a patch to a computer system, wherein the patch includes content to add to the computer. A computer object is generated to include configuration information on the determined installed components. At least one patch includes content to add to the computer and is capable of being associated with at least one realization, wherein each realization defines a state of the computer. For each realization, a determination is made from the configuration information in the computer object as to whether the state defined by the realization exists in the computer. Data is written to the computer object indicating whether the state defined by the realization exists on the computer. The computer object is used to determine whether each patch is compatible with the installed components of the computer.