Abstract: Apparatus and methods are disclosed for identifying differences in objects of a computing device using definitions expressed in vulnerability assessment languages such as Open Vulnerability and Assessment Language (OVAL). In one example of the disclosed technology, a method includes receiving criteria for evaluating the computing device using an agent. The criteria specify object tests used to generate associated state values based on states or status of the tested objects. The criteria are evaluated and first state values generated by performing the object tests are stored as expected values for object tests. The criteria are then evaluated by re-performing the object tests, and second state values thereby generated are compared to the first state values. One or more differences between the first and second state values can be identified and reported to, for example, a monitor server.