Verifying the validity of a parametric solution might still require testing every single case. So, the challenge of building a parametric model is to untangle the interdependencies created by different requirements and find a set of rules that is as simple as possible while remaining flexible enough to accommodate every occurring case. This usually starts with finding the extreme cases – for example, the joints with extreme angles or the members with highest loads – and developing a parametric solution that can handle those as well as all intermediate cases. And, as soon as the underlying grid becomes non-regular, both components and joints must be adjusted to the geometrical situation at every grid position, rendering every piece unique. To save designers from manually modelling thousands of components, the concept of ‘parametric modelling’ was introduced: instead of describing the final result as a model, the process of modelling itself is described. A sequence of instructions (an algorithm) generates output (a detailed model) based on input (a set of parameters). Abstraction in this context means to systematically develop a general solution suiting all individual components. By varying the input values, different output can be generated.