Machines, systems and methods for providing a job description for execution in a computing environment, the method comprising receiving a job description, wherein the job description defines a set of job alternatives based on an order of priority and conditions associated with execution of the job alternatives; processing the job alternatives to determine whether resources for executing at least a first job alternative are available, considering respective first conditions defined in the job description for the first job alternative; selecting a first computing element implemented in a virtualized computing environment, wherein the selected first computing element has sufficient resources to satisfy resource requirements defined in the job description for the first job alternative; and submitting the job to the first computing element for execution.