Software Requirements Engineering for RTS and Embedded Systems

Software Requirements Engineering for RTS and Embedded Systems B. Ramamurthy Page 1 9/9/2020

Topics • • Requirements engineering process State machines Event-driven programming Table-driven methods Page 2 9/9/2020

Requirements-Engineering Process • Deals with determining the goals, functions, and constraints of systems, and with representation of these aspects in forms amenable to modeling and analysis. Page 3 9/9/2020

Types of requirements • • Standard scheme for realtime systems is defined by IEEE standard IEEE 830. It defines the following kind of requirements: I. Functional II. Non-functional 1. 2. 3. 4. 5. Page 4 External interfaces Performance Logical database Design constraints (ex: standards compliance) Software system attributes Reliability, availability, security, maintainability, portability 9/9/2020

Design methods: Finite state machines • Finite state automaton (FSA), finite state machine (FSM) or state transition diagram (STD) is a formal method used in the specification and design of wide range of embedded and realtime systems. • The system in this case would be represented by a finite number of states. • Lets design the avionics for a drone aircraft. Page 5 9/9/2020

Drone aircraft avionics (simplified) else TAK MA else NAA Page 6 LO MA: Mission Assigned else TD: Target Detected LO: Locked On EE: enemy Evaded NAV ED: Enemy Destroyed MC: Mission Complete TD NAE MC ED LAN EE TAK: Take off NAV: Navigate NAE: Navigate & Evade NAA: Navigate & Attack LAN: Land 9/9/2020

Finite State Machine (FSM) • M = five tuple { S, i, T, Σ, δ } • S = set of states • i = initial state • T = terminal state (s) • Σ = events that bring about transitions • δ = transitions • Lets do this exercise for the avionics for fighter aircraft Page 7 9/9/2020

State Transition table MA TAK LO NAA MC NAE LAN EE ED NAE NAV NAV NAE TD NAA LAN Page 8 9/9/2020

Lets write the embedded system • Use the table to code a function with case statement • Or write a table-driven code • Which is better and why? • Try your binary game using FSM method Page 9 9/9/2020