# Glossary

- Sampling
- In the context of the GUI a Sampling is the same as a Case. It is based on a unique subset of variables.

In general, Sampling is synonymous with Point Selection or Experimental Design. - Saturated design
- An experimental design in which the number of points equals the number of unknown coefficients of the approximation. For a saturated design no test can be made for the lack of fit.
- Scale factor
- A factor which is specified as a divisor of a response in order to normalize the response.
- Sensitivity
- See Design sensitivity.
- Sequential Random Search
- An iterative method in which the best design is selected from all the simulation results of each iteration. A Monte Carlo based point selection scheme is typically applied to generate a set of design points.
- Simulation
- The analysis of a physical process or entity in order to compute useful responses. See Function evaluation.
- Slack constraint
- A constraint with a slack variable. The violation of this constraint can be minimized.
- Slack variable
- The variable which is minimized to find a feasible solution to an optimization problem, e.g. e in: min e subject to g j ( x) ≤ e; e ≥ 0. See Strictness.
- Solver
- A computational tool used to analyze a structure or fluid using a mathematical model. See Discipline.
- Space Filling Experimental Design
- A class of experimental designs that employ an algorithm to maximize the minimum distance between any two points.
- Space Mapping
- A technique which uses a fine design model to improve a coarse surrogate model. The hope is, that if the misalignment between the coarse and fine models is not too large, only a few fine model simulations will be required to significantly improve the coarse model. The coarse model can be a response surface.
- Stage
- A distinct step or operation in a process which typically reads input, processes the input and produces a result. Example: run a solver.

Different stages can be dependent on one another. - Stage directory
- A subdirectory of the work directory that bears the name of a solver and where database files resulting from extraction and the optimization process are stored.
- Stochastic
- Involving or containing random variables. Involving probability or chance.
- Stopping Criterion
- A mathematical criterion for terminating an iterative procedure.
- Strictness
- A number between 0 and 1 which signifies the strictness with which a design constraint must be treated. A zero value implies that the constraint may be violated. If a feasible design is possible all constraints will be satisfied. Used in the design formulation to minimize constraint violations. See Slack variable.
- Subproblem
- The approximate design subproblem constructed using response surfaces. It is solved to find an approximate optimum.
- Subregion
- See region of interest.
- Successive (or Sequential) Approximation Method
- An iterative method using the successive solution of approximate subproblems.
- System identification
- A procedure in which a numerical model is calibrated by optimizing selected parameters in order to minimize the residual error with respect to certain targeted responses. The targeted responses are usually derived from experimental results.