0.0 Data Process accs0.trg 0.0~~Maintain~Automobile~Speed This is the central data process on the context diagram and represents all logicand processing for the automobile cruisecontrol system (ACCS). It functionally decomposes to the level #1 chart : accs0.trg. level 0 Context Diagram 1 Control Transform 1~~Monitor~Engine 2 Data Process accs2.trg 2~~Maintain~Active~Status 2.1 Control Transform 2.1~Determine~Mode Of~Operation 2.2 Data Process accs22.trg 2.2~Manage~Control~Mode 2.2.1 Control Transform a221.std 2.2.1~Control~Cruise~Control~Engagement 2.2.2 Data Process 2.2.2~Record~Rotation~Rate 2.2.3 Data Process 2.2.3~Increase~Speed 2.2.4 Data Process 2.2.4~Maintain~Constant~Speed 2.2.5 Data Process 2.2.5~Return to~Previous~Speed 2.3 Data Process accs23.trg 2.3~Manage~Learning~Mode Manages the learning mode function basedon the measurement of 1 mile under control of the start/stop measured mile commands from the driver. 2.3.1 Control Transform 2.3.1~~Control~Learning~Mode 2.3.2 Data Process 2.3.2~~Accumulate~Rotations Accumulates the number of engine rotat- ions counted between the start and end of the measured mile. 2.3.3 Data Process 2.3.3~~Set~Conversion~Factor 2.4 Data Process 2.4~Report~Current~Speed Accumulated Rotations Data Store Accumulated~Rotations Async Call Asynchronous Call Asynchronous Call Automobile Speed Data Flow Time Continuous Automobile Speed Brake External Entity Brake~Pedal This is the automobile's brake pedal. When depressed, it shall result in disengagement of the cruise control system. Brake Control Flow Time Discrete * Values : [Braking | Not Braking] * Braking Signal indicates whether the brake pedalis depressed or not. The cruise control system shall be disengaged if the brake pedal is depressed. Boolean Clutch External Entity Clutch~Pedal This is the automobile's clutch pedal. If depressed, thereby disengaging the clutch, the cruise control system shall be disengaged. Clutch Control Flow Time Discrete * Values : [Depressed | Not Depressed] * Clutch Pedal~Depressed Signal indicates whether the clutch pedal is depressed, thereby disengaging the clutch, or not. The cruise control system shall be disengaged if the brake pedal is depressed. Boolean Connect #1 STC Connection CONNECTION (Call) Cruise Control State Control Flow Time Discrete = [Cruise Control On | Cruise Control~ Off] Cruise Control~On/Off Signal indicates whether the cruise control system controller is turned on or off. Boolean Decrease Speed Control Flow Time Discrete Decrease Speed Signal indicating that the accs is to decrease the automobile's speed on command from driver. The speed shall be decreased by 1 mph each time the accel button is 'tapped' rather than held down. Boolean Displays Data Flow Time Discrete = Automobile Speed + Engine Speed +~ Fuel Level Instrument~Displays Used to indicate various data to the driver via the dash display. Includes vehicle speed, engine speed and fuel level. Drive Shaft External Entity Drive~Shaft The drive shaft transfers engine rotat- ions to the wheels, via the gearbox. A sensor mounted to the drive shaft, afterthe gearbox, is used to determine the road speed. Driver External Entity Driver The driver sits in the automobile and performs such functions as starting the engine, turning-on the cruise control, controlling the brake and clutch, controlling the radio, gesticulatin at other motorists and looking out for cops! Driver Commands Control Flow Time Discrete = Increase Speed + Decrease Speed +~ Resume + Cruise Control On/Off +~ Start/End Measured Mile Driver Commands Set of signals from the cruise control system console, controlled by the driver Boolean Enable/Disable 2.1 Control Flow Time Discrete Enable/Disable Enable/Disable 2.2 Control Flow Time Discrete Enable/Disable Enable/Disable 2.2.1 Control Flow Time Discrete Enable/~Disable Enable/Disable 2.2.3 Control Flow Time Discrete Enable/~Disable Enable/Disable 2.2.4 Control Flow Time Discrete Enable/~Disable Enable/Disable 2.2.5 Control Flow Time Discrete Enable/~Disable Enable/Disable 2.3 Control Flow Time Discrete Enable/Disable Enables and Disables the control transform for process 2.3. Enable/Disable Enable/Disable 2.4 Control Flow Time Discrete Enable/Disable Engine External Entity Engine This is the automobile's engine. The cruise control system shall only operatewhile the engine is turned-on and running. Engine State Control Flow Time Discrete * Values : [Running | Not Running] * Engine~Running Signal indicates whether the engine is turned on or off. The cruise control system shall operate only while the engine is turned-on and running. Boolean External External Device EXTERNAL~DEVICE Fuel Level Data Flow Time Discrete Fuel Level Indicates the current level of fuel in the tank, from which the amount of fuel remaining can be determined for display to the driver via the fuel gauge. Fuel Tank External Entity Fuel Tank Contains the fuel needed to run the engine. Function #1 Function FUNCTION~SYMBOL Function #2 Defined Function Level #~~PRE-DEFINED~FUNCTION~(Named) Function #3 Iterative Function REPETITIVE~FUNCTION~(ITERATIVE) Function #4 Decision Function DECISION~FUNCTION~(Transaction~Center) Function #5 Inclusive Function INCLUSIVE~FUNCTION Gearbox External Entity Transmission~Gearbox Transfers engine power to the wheels via the drive shaft. Indication is made as to whether or not top gear is selected. Increase/Decrease Speed Control Flow Time Discrete = Increase Speed + Decrease Speed Increase/Decrease~Speed Signals from the cruise control switch indicate whether the driver is request- ing an increase or decrease in speed Boolean Increasing Speed Control Flow Time Discrete = [Start Increasing Speed | Stop~ Increasing Speed] Start/Stop~Increasing Speed Signals used to indicate whether the cruise control system is to increase the automobile speed or not, on command of the driver. The accs shall increase speed in 1 mph increments while the accel button is depressed. Boolean Initial State State Initial~State Input Transition Transition Input (Initial) Transition~C:Initial Event~-----------------~A:Initial Action Measured Mile Control Flow Time Discrete = [Start Measured Mile | End Measured~ Mile] Start/End~Measured Mile Signals indicate whether the start or end of a measured mile is indicated allowing for calibration of the accs by measuring the time taken to travel one mile. Boolean Module #1 Module MODULE~SYMBOL Module #2 Defined Module Name/Level #~~MODULE~(Named) Output Transition Transition Final (Output) Transition~C:Final Event~--------------~A:Final Action Previous Speed Reached Control Flow Time Discrete Previous Speed~Reached Resume Control Flow Time Discrete Resume Signal indicates that the cruise controlsystem resume button has been pressed. The accs shall revert to taking over control of maintaining automobile speed, at the previously set speed. Boolean Rotation Rate Data Flow Time Continuous * Units : revolutions per minute (rpm) * Rotation Rate Indicates the rate of rotation of the drive shaft, from which can be determin-ed the road speed of the automobile. Vraiable Rotation Rate Setpoint Data Store Rotation~Rate~Setpoint Rotation Rate Setpoint Data Flow Time Discrete SM 147 Split/Merge SM 152 Split/Merge SM 181 Split/Merge Speed Data Flow Time Continuous * Units : miles per hour * Automobile~Speed Indication of the current speed of the automobile to the driver via the speedometer. Variable Speed Conversion Factor Data Store Speed~Conversion~Factor Speed Conversion Factor Data Flow Time Discrete * Units : # rotations per mile * Speed Conversion~Factor Conversion between the rotation rate of the wheels and the speed of the car. Used to calibrate automobile speed. Start/End Measured Mile Control Flow Time Discrete = [Start Measured Mile | End Measured~ Mile] Start/End~Measured Mile Signals from the driver indicating that a measured mile is being timed for calibration of automobile speed. Boolean State #2 State State #2 Store Store DATA STORE Throttle External Entity Throttle This is the engine throttle. Opening it increases the engine speed and hence there is a corresponding increase in automobile speed. Closing it has the opposite effect, decreasing automobile speed. Under control of driver or accs, if selected. Throttle Control Data Flow Time Continuous * Units : Percentage of maximum * Throttle~Control Used to open the engine throttle to the desired position, thereby increasing thespeed of the engine, in turn changing the automobile road speed. While the cruise control system is engaged, this is under it's control. Vraiable Throttle Position Data Flow Time Continuous * Units : percentage of maximum * Throttle Position Indicates the current position of the throttle from which the desired speed of the automobile can be determined. Variable Transition #1 Transition Transition #1~C:Event #1~-----------~A:Action #1 Transition #2 Transition Transition #2~C:Event #2~-----------~A:Action #2 Transition #3 Transition Transition #3~C:Event #3~-----------~A:Action #3 Transition #4 Transition Transition #4~C:Event #4~-----------~A:Action #4 Trigger 2.2.2 Control Flow Time Discrete Trigger c connect STC Connection c couple 1 Control Couple CONTROL FLOW~PARAMETER~(Down) c couple 2 Control Couple CONTROL FLOW~PARAMETER~(Up) connection STC Connection d couple 1 Data Couple DATA FLOW~PARAMETER~(Update) d couple 2 Data Couple DATA FLOW~PARAMETER~(Down) u connect STC Connection Explodes To Attribute object~explodes to Defines the underlying definition of a chart object. May be a lower level chart filename in the case of a symbol, or a composite record structure in the case of a flow. May also be a text file. Description Attribute object~description Textual description of an object on the chart and defined in the data dictionary Type Attribute object type Defines the type of an object on a chart. This is the sub-key field for a data dictionary entry, used for finding and extracting the object record for a specific object type. Sub-key Label Attribute object~label This is the text (formatted) label which appears inside (for symbols) or next to (connections and couples) an object on the chart. It is inherited from the D/D record entry for an identified object. Identifier Attribute object~identifier This is the attribute which, along with the object type, is used to uniquely define an object entry in the data dictionary. This allows object record definitions (attributes) to be used on any other (similar type) object on any other chart. Key Object Entity Objects An object is a symbol (data process, data store etc.) or connection (data flow, connection etc.) or couple (data or control) flow which can appear on anychart type. Each chart type has a set ofobjects which can be added, manipulated and accociated DFD Entity Data Flow~Diagram A Data Flow Diagram (DFD) is made up of a set of data processes, data stores, terminators etc. connected by data flowsand interfaces. DFDs are udes to depict the functional breakdown of a system andthe internal and external flow of information. Store Entity Store A data store may appear on a data flow diagram and is used to store the data output by a process until another process needs it. Data Process Entity Process A data process transforms input data flows into output data flows and represents a particular function of the system being defined by the DFD. Data Flow Entity Flow A data flow is used to pass 'packets' ofdata between data processes, stores and terminators. Terminator Entity Terminator A terminator represents a 'real world' entity, external to the system, with which the system exchanges data. Interface Entity Interface An interface data flow is an off-page data flow and represents data flows which are exchanged either with externaldevices (terminators) or processes or stores defined on another DFD. defines Relationship defines A Data Flow Diagram (DFD) is made up of a collection of objects such as data processes, data stores, terminators and data flows. is Relationship is A DFD may itself be defined to be an object if it is the 'child' chart of a process defined on the higher level 'parent' chart. is store Relationship object~is store A DFD may contain one or more a data store objects. is process Relationship object is~process A DFD may contain one or more data process objects. is flow Relationship object~is flow A DFD may contain one or more data flow and/or interface objects. is terminator Relationship object is~terminator A DFD may contain one or more terminatorobjects, normally restricted to the top level context diagram only. is text Relationship object~is text~block A DFD may contain one or more text blockobjects used for annotation or title etc. purposes. Text Entity Text Block Text blocks may be palced anywhere on a DFD for use as a title, annotating the chart etc. Text blocks are not associated with any other chart objects. Floppy Disk Drive External Entity Floppy Disk~Drive(s) Mouse External Entity Mouse Hard Disk External Entity Hard Disk~Drive and~Controller Disk Cache Data Store Disk Cache Keyboard External Entity Keyboard PC Data Process Personal~Computer~System Keyboard Buffer Data Store Keyboard~Buffer Joystick External Entity Joystick Modem External Entity Modem Printer External Entity Printer Video Display External Entity Video~Display Plotter External Entity Plotter Print Spooler Data Store Print~Spooler Maintaining Speed State Maintaining~Speed Increasing Speed State Increasing~Speed Start Increasing Speed Transition C:Start Increasing Speed~A:Disable Maintain Constant~ Speed~ Enable Increase Speed Stop Increasing Speed Transition C:Stop Increasing Speed~A:Disable Increase Speed,~ Trigger Record Rotation Rate,~ Enable Maintain Constant Speed Enabled Transition C:Enabled~A:Trigger Record Rotation Rate~ Enable Maintain Constant Speed Interrupted State Interrupted Braking Transition C:Braking~A:Disable Increase Speed Resuming Transition C:Resume~A:Enable Return to~ Previous Speed Braked Transition C:Brake~A:Disable Return to~ Previous Speed Brake Transition C:Brake~A:Disable 'Maintain~ Constant Speed' Resuming Speed State Resuming~Speed Reached Previous Speed Transition C:Previous Speed Reached~A:Disable Return to Previous~ Speed, Enable Maintain~ Constant Speed
