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Embed design intent in a model by using project-wide parameters to drive dimension and element instance parameters with the Global Parameters feature in Revit 2016 R2. A global parameter can measure dimensions and calculate formulas to drive dimensions and parameter values in other elements in the project.
Global Parameters comprise two classes: driving (DGP) parameters pushes its value into an element or instance parameter. A reporting (RGP) parameter can pull a value from a dimension and use that value in other global parameters via equations. With Global Parameters, you can use equality dimensions to constrain any dimensions, including those that are non-adjacent. Automate the positioning of one element based on the size of another element. Use Global Parameters to capture formulaic relationships directly in a model.