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, 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.
8. The method of claim 1 , wherein the step of generating the infrastructure model includes generating a Unified Modeling Language (UML) model of an infrastructure required to implement the IT system instance, the infrastructure including the hardware components, wherein the UML model of the infrastructure includes: a first node that represents an instantiation of a first physical device required in the infrastructure; a second node that represents an instantiation of a second physical device required in the infrastructure; a first artifact that represents one or more hardware specifications of the first physical device; a second artifact that represents a software package required to be installed on the first physical device; one or more attributes that provide information about a configuration of the first node, the second node, the first artifact or the second artifact; a communication path that represents a connectivity between the first and second nodes and indicates a communication protocol required for the connectivity; association lines that indicate that the first and second artifacts are part of the first node; a deployment specification that represents a security zone or a location of the infrastructure; and an execution environment that represents an operating system or a bundle of software packages represented by artifacts of the UML model.