1. A method of automatically deploying an information technology (IT) system instance having hardware and software components, the method comprising the steps of: based on components consisting of system context diagrams, component models, operational models, data flow diagrams, and use cases describing functional requirements of the IT system instance, generating, by the computer, an application model of the software components; based on the application model and the use cases, generating, by the computer, an infrastructure model of infrastructure components; based on the application model and the infrastructure model, generating, by the computer, a computer file in a markup language, wherein the computer file includes a design of the IT system instance having the hardware and software components, and further includes first instructions for accessing first assets stored in an infrastructure runtime source library and second instructions for accessing second assets stored in a software source library, and wherein the first assets specify the hardware components and the second assets specify the software components; and exporting, by the computer, the computer file in the markup language to a deployment tool, wherein a result of the exporting the computer file to the deployment tool is an automatic deployment of the IT system instance based on carrying out the first and second instructions included in the computer file to access the first and second assets stored in the infrastructure runtime source library and the software source library, respectively.