4.5.10 The project manager shall validate the software system on the targeted platform or high-fidelity simulation.
Typically, a high-fidelity simulation has the exact processor, processor performance, timing, memory size, and interfaces as the target system.
1.2 Applicability Across Classes
Validation is a process of evaluating work products to ensure that the right behaviors have been built into the work products. The right behaviors adequately describe what the system is supposed to do and what the system is supposed to do under adverse conditions. They may also describe what the system is not supposed to do.
Validation is performed to assure that the specified software systems fulfill their intended use when placed on the targeted platform in the target environment (or simulated target environment). The methods used to accomplish validation on the actual target platform or in a high fidelity simulator may include aspects that were applied to previous software work products (requirements, designs, prototypes, etc.). The use of these methods provides continuity of results through the assembling system. The use of the high-fidelity or targeted system allows the software developers to check systems level interfaces, memory performance and constraints, event timing, and other characteristics that can only be evaluated properly in the real system or near-system environment (see SWE-055). Validation activities include preparation, performance, analysis of results, and identification of corrective action. Validation at the systems level ensures that the correct product has been built.
The basic validation process is shown below with the steps addressed by this requirement highlighted:
Validation, as used in this requirement, addresses the following:
See SWE-055 for additional information on requirements validation during the concept, design, coding, and initial testing phases of the software development life cycle.
Once the software work products have been integrated into a software system, validation activities are concentrated on systems-level effects, interactions, interfaces, and the overall behavior of the system (i.e., whether the system is providing for and meeting the needs of the customer). This level of validation can be accomplished in either an actual operational environment with the use of the targeted platform, or if this combination is not viable, on a high-fidelity simulator. A high-fidelity simulation typically has the exact processor, processor performance, timing, memory size, and interfaces as the flight unit.
The following scenarios provide additional considerations for selection of the most appropriate validation approach at the systems level:
Also, consider user-created operational scenarios, when appropriate. They can be a valuable tool in either simulated or operational environments.
4. Small Projects
The small project does not normally involve highly complex platforms, so it is generally easier and cheaper to validate software systems on the targeted platform. However, the environment for space systems will typically need to be simulated during validation for projects regardless of size. When using simulated platforms, small projects are advised to look for existing tools rather than creating their own.
6. Lessons Learned
The NASA Lessons Learned database contains the following lessons learned related to simulations: