Requirements Analysis of Real-Time Central Heating Control System V10

This paper presents a requirements analysis specification of a Real-Time System; Central Heating Control System V10. The result of the analysis is presented in form of Data Flow Diagrams (DFDs), Entity Relationship Diagrams (ERDs), RT-SASD modifications and components, Control Flow Diagram extensions (CFDs), Process Specifications (PSPECs), Data/Requirements Dictionary and Control Specifications (CSPECs).

Heating Control System V10
(CHCSV10)
Assignment 1
Real Time Analysis

Introduction
This paper presents a requirements analysis specification of a Real-Time System; Central
Heating Control System V10. The result of the analysis is presented in form of a;
 Data Flow Diagrams (DFDs)
 Entity Relationship Diagrams (ERDs)
 RT-SASD modifications and components
 Control Flow Diagram extensions (CFDs),
 Process Specifications (PSPECs)
 Data/Requirements Dictionary
 Control Specifications (CSPECs)
Entity Relationship Diagram

Control/Data Flow Diagram (Level 0)

Control/Data Flow Diagram (Level 1)

Process 1 Control/Data Flow Diagram (Level 2): Heating
Ducts
Process 2 Control/Data Flow Diagram (Level 2): Gas Meter
Supply

Process 3 Control/Data Flow Diagram (Level 2): Heating
Unit

Process 4 Control/Data Flow Diagram (Level 2): Heating
Unit Fan
Process 5 Control/Data Flow Diagram (Level 2): System
Clock

Process 6 Control/Data Flow Diagram (Level 2):
Temperature Detector
Process 7 Control/Data Flow Diagram (Level 2): Display

Control Specification (Process Activation Table)
 Only for starting the heating when temperature falls below the set value AND
stopping the heating when the temperature goes beyond the specified value during
the heating process.
Current temp below
specified level?
Activate Activate Activate Activate Activate
TRUE 1.2 2.2 3.3 4.2 7.1
FALSE - - - - -
New temperature is
above specified level
Activate Activate Activate Activate Activate
TRUE 1.3 2.3 - 4.3 7.1
FALSE 7.1 - - - -
Duck was manually
closed?
Activate Activate Activate
TRUE 7.1 - -
FALSE 1.2 7.1 -
Duck available Activate Activate Activate
TRUE 1.2 7.1 -
FALSE 7.1 - -
Gas meter available? Activate Activate Activate
TRUE 2.2 7.1 -
FALSE 7.1 - -

State Machine Diagrams
Heating Unit Process

Gas Meter Supply Process
Heating Unit Fan

Process Specification
 Verify If current temperature is below the specified value
get specified_temp_level;
Read current_temp
if(current_temp < specified_temp_level)
activate_heating_unit = true
else
activate_heating_unit = false
Current temperature is compared with the specified temperature;
if the current temperature falls below the specified value; the heating process
is activated; which requires a number of processes.
Verify availability of heating components to activate heating
get heating_unit_fans_status
get heating_unit_status
get gas_meter_supply_status
get heating_ducts_status
get time
get day
if(heating_unit_fans_status = available
AND heating_unit_status = available
AND gas_meter_supply_status = available
AND heating_ducts_status != manually_closed){
open_ducts = true
start_gas_flow =true
start_fans =true

start_heating_unit=true
}
Heating can only start if the temperature falls below the specified value, and the components
are available. This is dependent on time and day.
Combined process to initiate heating
get specified_temp_level;
Read current_temp
while(current_temp < specified_temp_level) {
get heating_unit_fans_status
get heating_unit_status
get gas_meter_supply_status
get heating_ducts_status
get time
get day
if(heating_unit_fans_status = available
AND heating_unit_status = available
AND gas_meter_supply_status = available
AND heating_ducts_status != manually_closed){
open_ducts = true
start_gas_flow =true
start_fans =true
start_heating_unit=true
}
Read current_temp
if(manual_Input)
break;
}

This code block uses a while loop to represent the continuous nature of the process of
checking the temperature, and taking corrective measures if the temperature falls below the
set limit. The code runs in an endless loop and can only be interrupted if a manual input is
encountered; in which case the execution breaks the loop.
Store New Temperature Value
Get current_temperature;
new_temperature = current_temperature
This updates the new temperature value with the current temperature.
Open Heating Duct
Get heating_duct_status
if(heating_duct_status != manually_closed)
heating_duct_status = open
A heating duct can only be opened if it was not manually closed. This code checks if the duck
was closed manually before opening the duck.
System Control Panel
 Listening and executing commands
new_command = command
switch(command)
{
case Configure Temperature Detector:
display options: Celsius , Fahrenheit
get user_selection;
set temperature_metrics = user_selection
break;
Case Set Heating Program:
set day = get selected_day;
set time_period = get_time_period;

set min_temp = get_ temp_lower_limit;
set max_temp = get_temp_upper_limit;
save settings;
break;
Case Manually Change Heating program:
set day = get selected_day;
set time_period = get time_period;
set min_temp = get_temperature_entered;
Case Turn System Off:
close_ducts
stop_gas_supply
stop _heating_fan
stop_heating_unit
set heating_fan_status = unavailable
set heating_unit_status = unavailable
display ducts_status
display gas_supply_status
display heating_fan_status
display heating_unit_status
break;
Case Turn System On:
open_ducts
set heating_fan_status = available
set heating_unit_status = available
display ducts_status
display gas_supply_status
display heating_fan_status
display heating_unit_status
}
Data Dictionary

Schedule Events
Name Description
Every 5 minutes, for duck
current state
An event initiated by the system after every 5 minutes to
check the status of the heating duck
Every 30sec, for Gas Meter
Supply Status
An event initiated by the system after every 30 seconds to
retrieve the status of the Gas Meter Supply Status
Every 30 Sec for Heating Unit
status
An event initiated by the system after every 30 seconds to
retrieve the current status of the heating unit
Dictionary for all processes
close_duct Command to initiate closing of the duct
open_duct Command to initiate opening of the duct
duct_status Data representing current state of the heating duct
manually_closed Data that represents state of the heating duct that was
manually closed and cannot be opened by the system
command User inputs through the control panel
start_gas_flow Command to initiate flow of gas into the heating unit
stop_gas_flow Command to inform the gas meter to shut the gas flow
current_gas_supply_status State of the gas supply meter
current_date, Data representing the day's date
current_time Data representing time
set_heating_unit_fan_state Command to set the state of the heating unit
fan_state Data representing the current state of the fan
set_heating_unit_state Command to set the state of the heating unit
current_heating_unit_state Data representing the current state of the heating unit
current_temp Data representing the current temperature
message Information sent to the display board for display purposes.
System Control Panel The interface that will allow users to enter configurations
and interact with the system
System Display The system's point of outputting the status and other
information to the user
System Temperature Detector Component to detect the environmental temperature
System Clock Component that provides the system with the current time ,
date and day.
Heating Unit Fan Component that aids in circulating the heat, emitted to
regulate the temperature
Heating Unit The unit responsible for generating heat that is used to raise
the temperature of a room, when temperatures fall below
specified limit
Gas Meter Supply Component that interfaces the system to the external gas
supply, and records gas usage
Heating Duct Component used to blow heated air
Conclusion

An analysis of a real-time system requirements has been presented in this paper. The system
under review is a Central Heating Control System V10. The result of the analysis is presented
in form of a; Data Flow Diagrams (DFDs) , an Entity Relationship Diagrams (ERDs), RT-
SASD modifications and components , Control Flow Diagram extensions (CFDs), Process
Specifications (PSPECs) , Data/Requirements Dictionary and a Control Specifications
(CSPECs).

References
Pressman, R. S. (2010). Software engineering: a practitioner's approach. Palgrave
Macmillan.
Kendall, K. E., & Kendall, J. E. (2010). Systems analysis and design. Prentice Hall Press.
Laplante, P. A., & Ovaska, S. J. (2011). Real-time systems design and analysis: tools for the
practitioner. John Wiley and Sons.