Design

While mentioning design for projects in the guidance of DO-178B, it is worth mentioning og DO-331Model Based Development and Verification document with the new established DO-178C document because model based development will be involved in current and future designs. If we follow the model based development, we will have to keep to DO-331. Because modeling is an issue on its own, we should try to elaborate on description of the modeling and how to use it in DO-331 document rather than modeling details. Whether a model based approach is followed or not , design consists of 2 parts in the projects in guidance of DO-178B/C  they are called as software design and low level requirements. 

Software design is a text and modal expression that most of us are familiar. Software low level requirements are colloquially mortar of design, and they are where the question of how the work based on function is answered. At this point, model elements can be used for elucidating all or some of requirements or design steps of software system. This usage divided into two part like “Specification” and “Design”. High level abstract models for functionality, performance and safety are created in Specification part. Created model elements in this part don’t express detailed parts such as data structure, data transfer, control transfer, but they elaborate functionality and express functionally proceedings of the system. To give an example on behalf of simplistic, if our modeled system is a microwave oven, main design elements are modeled for its shutter, emitter, timer, and detailed indicators are not expressed such as how many watt microwave’s emitter will be, how many digits will be on the clocks’ digital screen, etc. in this part. 

To sum up, any model projection relating to design details should not be created in the Specification. In case of using models that we created in Specification as high level requirements, all the conditions that should be completed for high level requirements mentioned in DO-178B/C documents are valid as same as model elements. Additionally, all the “specification” models should be “traced” to software high level requirements.