Team Skill 1 Analyzing the Problem Systems Engineering (7) 1

Systems Engineering Systems Engineering approach to Software Engineering ▫Some of the same concepts can be applied Best way to solve a large problem? ▫Divide it into “logical” smaller sections In dividing the system in logical grouping you create subsystems that can encapsulate functionality ▫Mitigate Risk ▫Mitigate Change Impact ▫Adhere to Compliance/Regulations (credit card functionality) 2 Copyright Leffingwell, Widrig, & SIS Faculty

Systems Engineering Figure 7-3 ▫A system composed of 2 subsystems one of which contains 2 subsystems 3

Systems Engineering For example, a car has subsystems like: ▫Power train  Engine, Transmission  Axle, Differential ▫Suspension  Wheels  Tires  Shocks or Struts  Springs 4 Copyright Leffingwell, Widrig, & SIS Faculty

Systems Engineering Subsystems ▫Can be broken into layers  Done to organize specific functions Subsystems usually have specific functions to perform ▫Design Patterns – Encapsulation/Cohesion 5 Copyright Leffingwell, Widrig, & SIS Faculty

Systems Engineering Subsystems have many benefits ▫One is they can control the level of exposed functionality ▫Figure 7-4  Interface between 2 subsystems 6

Systems Engineering Requirements can be used to guide selection of commercial components for your system as well ▫Servers ▫Database ▫Networking Devices ▫… 7 Copyright Leffingwell, Widrig, & SIS Faculty

Systems Engineering Software is becoming a part of nearly every industry ▫Even areas which had no reason for software in the last few decades ▫So they now care about software requirements and software engineering ▫Software costs dominant balance sheet in many companies  Software success becomes a critical success factor for the company as a whole 8 Copyright Leffingwell, Widrig, & SIS Faculty

Systems Engineering Systems engineering places greater emphasis on ▫ Entire life cycle cost for a system  Maintenance  Sun setting ▫Previous models had left this out only focused on  Development costs/Initial Costs 9 Copyright Leffingwell, Widrig, & SIS Faculty

Systems Engineering How does this help with defining the system? ▫Understand subsystems and how they interact ▫Ability to hide information by using subsystems ▫Isolate high risk functionality ▫Add additional features as they arise as subsystems 10 Copyright Leffingwell, Widrig, & SIS Faculty

Systems Engineering Key for success in Systems Engineering ▫All subsystems must be compatible with the current system ▫Design subsystems so the can be created by reasonably sized teams ▫Logically distribute functionality across subsystems ▫Reliable testing can be performed on your subsystem  Libraries of Unit tests, integration tests, automated tests 11

Systems Engineering Best practices ▫Don’t go subsystem CRAZY! ▫Design Using Object Oriented principles and design patterns  Encapsulation  High Coupling  Low Cohesion ▫Manage your requirements!!  System Level requirements should trace down to subsystem level ▫Try to predict future change?  What we have right now changes enough  Design flexibly! 12

Systems Engineering Figure 7-6 ▫HOLIS with Actors ▫High-level problem statements on p

Systems Engineering Figure 7-7 ▫HOLIS with subsystems and actors ▫HOLIS constraints on p