9. A computer program product, comprising: a computer readable hardware memory; and a computer readable program code stored in the computer readable memory, the computer readable program code containing instructions that are carried out by a processor of a computer system to implement 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 system, an application model of the software components; based on the application model and the use cases, generating, by the computer system, an infrastructure model of infrastructure components; based on the application model and the infrastructure model, generating, by the computer system, a computer system file in a markup language, wherein the computer system 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 system, the computer system file in the markup language to a deployment tool, wherein a result of the exporting the computer system 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 system file to access the first and second assets stored in the infrastructure runtime source library and the software source library, respectively, wherein the step of generating the application model, the step of generating the infrastructure model based on the application model, the step of generating the computer file in the markup language, the step of exporting the computer file to the deployment tool, and the automatic deployment of the IT system instance resulting from the step of exporting the computer file to the deployment tool are steps performed automatically in succession without a human-performed step being performed between any of the steps.
10. The program product of claim 9 , wherein the step of generating the application model includes representing the software components in a software component modeling language, wherein the step of generating the infrastructure model includes representing the hardware components in the software component modeling language, and wherein the design of the IT system instance is a single system model that links the infrastructure model and the application model based on the software component modeling language representing the hardware and software components.