The V-model is a graphical representation of a systems development lifecycle. It is used to produce rigorous development lifecycle models and project management models. The V-model falls into three broad categories, the German V-Modell, a general testing model and the US government standard. The V-model summarizes the main steps to be taken in conjunction with the corresponding deliverables within computerized system validation framework, or project life cycle development. It describes the activities to be performed and the results that have to be produced during product development. The left side of the "V" represents the decomposition of requirements, and creation of system specifications. The right side of the "V" represents integration of parts and their validation. However, requirements need to be validated first against the higher level requirements or user needs. Furthermore, there is also something as validation of system models. This can partially be done at the left side also. To claim that validation only occurs at the right side may not be correct. The easiest way is to say that verification is always against the requirements (technical terms) and validation always against the real world or the user needs. The aerospace standard RTCA DO-178B states that requirements are validated—confirmed to be true—and the end product is verified to ensure it satisfies those requirements. Validation can be expressed with the query "are you building the right thing?" and verification with "are you building it right?" Types There are three general types of V-model. V-Modell "V-Modell" is the official project management method of the German government. It is roughly equivalent to PRINCE2, but more directly relevant to software development. The key attribute of using a "V" representation was to require proof that the products from the left-side of the V were acceptable by the appropriate test and integration organization implementing the right-side of the V. General testing Throughout the testing community worldwide, the V-model is widely seen as a vaguer illustrative depiction of the software development process as described in the International Software Testing Qualifications Board Foundation Syllabus for software testers. There is no single definition of this model, which is more directly covered in the alternative article on the V-Model (software development). US government standard The US also has a government standard V-model which dates back about 20 years like its German counterpart. Its scope is a narrower systems development lifecycle model, but far more detailed and more rigorous than