| Useful simplification | A small model makes comparison affordable, while omitted observations or shared resources can reverse it. |
| Local and combined adequacy | Each contribution can satisfy its own conditions while their connection fails. |
| Result and history | Equal final values can accompany different intermediate answers, delays or failures. |
| Composition and allocation | Independent operations can overlap in principle while competing for the same equipment or attention. |
| Mathematical and practical grounds | A derivation establishes what follows from the model; reliance on the work requires the correspondence and assumptions to hold. |
| Comparison and development | A result can reject or retain an arrangement without constructing a replacement or requiring a new trial. |