> For the complete documentation index, see [llms.txt](https://infosys.selmotech.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://infosys.selmotech.com/selmo-solution/selmo-solution-en/selmo-documentation/5-logic-and-layers-dynamic/parameter-layer.md). # Parameter layer ## Flexibility without breaking the logic The **Parameter layer** supplements the Selmo model with **variable values**,\ without changing the logical flow or the behavior. The purpose of the parameter layer is to **enable flexibility**,\ without: * complicating logic * blurring states * losing determinism > **Parameters change values –**\ > **not the behavior.** *** ### Basic principle of the parameter layer In the Selmo model there is a clear separation: * **Logic layer**\ defines *when* something happens * **System layer**\ defines *what* is expected or monitored * **Parameter layer**\ defines *with which values* is worked The parameter layer: * contains **no logic** * contains **no states** * makes **no decisions** It provides exclusively **data**. *** ### times #### meaning Time parameters describe **process-relevant time values**, e.g.: * hold times * wait times * delays * time limits These times: * are used in the logic layer (e.g. in timer states) * influence the flow **quantitatively**, not qualitatively *** #### When it makes sense to parameterize times * when time is part of the process * when values vary depending on project or product * when adjustment should be possible without changing the model #### When times should not be parameterized * to compensate for unstable technology * as a substitute for missing feedback * to “fix” an incorrect model > **Time parameters must not mask logic.** *** ### Positions #### meaning Position parameters describe: * target positions of axes * reference points * mechanical end positions * setpoints for movements These values: * are used by zones and the system layer * do not **change**, *that* a movement takes place * only change *where to* or *how far* *** #### Purpose of position parameters * adaptation to different products * fine adjustment without changing the model * reusability of sequences > **The movement remains the same –**\ > **only the target value changes.** *** ### Repetitions #### meaning Repetition parameters define: * number of loop iterations * maximum retry attempts * test cycles They are typically used in: * repeater elements in the logic layer * controlled iterations *** #### Rules for repetitions * Repetitions must **be** limited * the meaning of the repetition must be explainable from a domain perspective * the parameter does not change **the flow**, but its scope Not allowed are: * infinite repetitions * parameter-driven flow changes *** ### Displays & inputs #### meaning The parameter layer can contain values that: * are displayed in the HMI * are entered by the operator * serve process monitoring These parameters: * are **not control elements for logic** * do not change state transitions * do not influence safety decisions *** #### Distinction from operator logic Inputs in the parameter layer: * are values, not commands * are validated, not interpreted * only take effect within defined limits > **The operator changes parameters –**\ > **not the model.** *** ### Determinism and parameters Despite parameterizable values, the system remains: * deterministic * reproducible * explainable Because: * logic is fixed * behavior is fixed * only numerical values change > **Same parameters + same states**\ > **always lead to the same behavior.** *** ### Typical mistakes in dealing with parameters Common mistakes are: * parameters replace logic * parameters control flow decisions * safety-relevant values are parameterizable * parameters are not limited or validated Rule of thumb: > **If a parameter changes the flow,**\ > **it is used incorrectly.** *** ### Summary The parameter layer: * enables flexibility * protects the logic * prevents model breakage * increases reusability It is: * not a shortcut * not a replacement for configuration * not a decision-making mechanism > **Parameters make models adaptable –**\ > **not unclear.** --- # Agent Instructions This documentation is published with GitBook. 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