1. A computer-implemented method of automatically deploying an information technology (IT) system instance having hardware and software components, said method comprising: a computer system generating an application model of said software components based on use cases associated with a plurality of requirements that includes functional and non-functional requirements of said IT system instance, wherein said generating said application model includes representing said software components in a software component modeling language; said computer system generating an infrastructure model based on said application model, wherein said generating said infrastructure model includes representing said hardware components in said software component modeling language; said computer system generating a computer file in a markup language, wherein said computer file includes a design of said IT system instance, 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 said first assets specify said hardware components and said second assets specify said software components; and said computer system exporting said computer file in said markup language to a deployment tool, wherein a result of said exporting said computer file to said deployment tool is an automatic deployment of said IT system instance based on carrying out said first and second instructions included in said computer file to access said first and second assets stored in said infrastructure runtime source library and said software source library, respectively.