According to Foster, an ER (Entity Relationship) is a kind of flowchart that illustrates how concepts or objects relate to each other in the system. ERDs provide a graphical starting point for software or database design. They can also be deployed to regulate information system necessities throughout a corporate. After a software has been deployed, the EERD can still be used referral in case any kind of business progression reengineering or debugging if required later (Foster, 2014).
In the figure below, is an EERD representing the Central Heating Control System V10 (CHCSV10) Project Real Time System. It indicates relationships of the heating system – CHCSV10 and other external objects such as operators/user. It depicts relationships of different entities with other entities. In addition, it provides cardinalities and modalities of the objects with respect to each other.
Thalheim defines cardinality in the framework of Entity Relationship Diagram as the amount of instances an entity must or can be linked to every instance of a different entity. For example in our ERD below, consider gas meter and heat unit as different entities, it can be clearly be seen the gas meter can supply large volumes of gas or at one point it may supply none (Thalheim, 2013). This can happen in case where gas is not available or gas is available but the supply is intentionally stopped.
Whereas cardinality denotes maximum number of connections among records of tables, modality denotes to the smallest number of record connections. Modality has only two options, that is, 1 being the least or 0 being the least. In our diagram, between gas meter and heat unit, we have a nullable modality which implies that gas can either be available or unavailable at one point.
Data and Control Flow Diagrams (DFD/CFDs)
Laplante & Ovaska defines a DFD (Data Flow Diagram) as graphical depiction of flow of information/data in a computerized system. It is normally used for Visualization of Information Processing in a system and is mostly used when analyzing a problem (Laplante & Ovaska, 2012). Douglass says a DFD can be deployed to provide end user of a system with physical idea of location of data they input has an effect upon structure of the entire system from order dispatch to top off (Douglass, 2014).
Process specifications (PSPECs)
The Dermaco notes that a process specification is created for data flow diagram and primitive processes of higher level. Process logic is represented in decision tables, structured English, specified formulas, decision trees, pseudocode or algorithms and is used in communication engineering requirements. In our PSPECS below, we use pseudocodes (DeMarco & DeMarco, 1999). Jorgensen defines pseudocode as detailed readable explanation of what algorithm or computing device program can do. They are formally-formatted ordinary language instead of programming language. A pseudocode are sometimes used as detailed step-by-step process of program development. In our automatic heating system environment, we have the following pseudocode for each process activity (Jorgensen, 2013).
Heating duct
IF heating duct closed manually
THEN
Open manually
ELSE IF heating duct closed by CHCSV10
THEN
Open by CHCSV10
END IF
IF central heating system operational
THEN
Heating duct report current state
ELSE IF
No reporting
END IF
IF new status is determined
THEN
Display new status on display
ELSE
Display previous status
END
GAS METER SUPPLY
IF gas available
THEN
Record number of cubic meters used
ELSE IF
Gas unavailable
THEN
Number of cubic meters used not recorded
ELSE IF
Gas available
Gas available
THEN
Gas supply stopped
ELSE
Gas unavailable
THEN
Gas supply stopped
IF central heating system operational
THEN
Gas meter supply reports current state
ELSE
Previous state is reported
END IF
Heating unit
IF heating unit is available
THEN
Central heating system is operational through CHCSV10
ELSE IF
Central heating system is operational through manual
ELSE IF unavailable
THEN
Central heating system not operational through CHCSV10
ELSE
Central heating system NOT operational through manual
END IF
IF new status determined
THEN
Display new information on the screen
ELSE
Previous information displayed on screen
END
System clock
If power available
Then
System clock on
Else if
Power backup energy is available
Then
System clock is on
End
If heating system is operational
Then
System clock send current status
Else
Don’t send message
End if
If system powered
Then
System clock requested date and day after 24hrs 12:00
Else
No request made.
End
System temperature detector
If power is available
Then
System temperature detector is on
Else if
Power back is available
Then
System temperature detector is on
End if
If central system is operating
Then
Temperature detector send current temperature status to display
Else
End
System display
System control parental
If
It is between 12:00:00 am and 5:59:00am
Then
Temperature range of 5 to 10 degrees Celsius
Else
Turn on heating system
End if
It is between 7:00:00am and 5:59:00pm
Then
Inclusive temperature of 15 to 20 degrees Celsius should be maintained.
Else if
It is between 6:00:00 and 11:59:00pm
Then
Temperature of 5 and 10 should be maintained
Else if
Manual heating is set
Then
Override automatic heating
Until
Heating program is scheduled to begin
Else if
Turn off Fan and heating Unit
Then
Turn on automatic heating system
Else
Update system display
End
Data storage
CHCSV10
If
<50% of ducts of total number of ducts open
Then
Turn on heating system
Else if
Temperature is below minimum of stipulated temperature range
Then
Premises heated
Until
Measured temperature is above range
Else
Status of one of the devices notifies that it is not heating
Else
System responds to a manually change heating command
Else
Turn of command is selected
End
Control Specifications (CSPECs)
As explained by Hatley & Pirbhai, CSPEC (control specification) refer to representation of the system behavior from a level from which it has been referenced. The control specification entails a state transition drawing that is usually sequential description of a behavior. In addition, it also entails a program activation table defined as the combinatorial specification of behavior (Hatley & Pirbhai, 2013).
The table below depicts the Process activation table whereas the figure depicts the state transition diagram of our CHCSV10 heating system.
Process Activation Table
|
Input Activities |
||||||
|
Gas notification |
0 |
0 |
1 |
1 |
0 |
0 |
|
Sensor event |
0 |
0 |
0 |
0 |
1 |
0 |
|
Start or Stop |
0 |
1 |
0 |
0 |
0 |
0 |
|
Display event status finished |
0 |
0 |
0 |
1 |
0 |
0 |
|
Time off |
0 |
0 |
0 |
0 |
0 |
1 |
|
Display action status Incomplete |
0 |
0 |
1 |
0 |
0 |
0 |
|
Output |
||||||
|
Temperature Signal |
0 |
0 |
0 |
0 |
1 |
0 |
|
Event activation |
||||||
|
Observe and regulate system |
0 |
1 |
0 |
0 |
1 |
1 |
|
Display statuses and messages |
1 |
0 |
1 |
1 |
1 |
1 |
|
User interaction |
1 |
0 |
0 |
1 |
0 |
1 |
|
Trigger/Neutralize heating system |
0 |
1 |
0 |
0 |
0 |
0 |
State Machine
Data Dictionary
Kendall defines data dictionary as a set of explanations of the information entities in a data model for advantage of program coders who need a reference point. Below are our data dictionary for our system (Kendall, 2014 ) (Creating the Data Dictionary, 2018)
(Litchfield, Berryman, & Thomas, 2013)
|
Data Structure |
|
|
Gas supply |
Gas supply = natural ordinary gas |
|
Gas supplied |
Gas supplied = ——— Flow rate: as needed Volume : as needed in cubic meters Other versions: filtered |
|
Gas Burnt |
Gas burnt = ——- Temperature: as needed in degrees Celsius Volume: as required Flow rate: moderate in m/s |
|
Fanned gas |
Temperature: as needed in degrees Celsius Volume: as required Flow rate: moderate in m/s |
|
Circulating gas |
Temperature: as needed in degrees Celsius Volume: as required Flow rate: moderate in m/s |
References
Creating the Data Dictionary. (2017, August 22).
DeMarco, P., & DeMarco, G. (1999). Building Architectural Models. Atglen: Schiffer Pub.
Douglass, B. P. (2014). Real-Time UML Workshop for Embedded Systems. Oxford: Newness.
Foster, E. (2014). Software Engineering: A Methodical Approach. New York City: Apress.
Hatley, D., & Pirbhai, . (2013). Strategies for Real-Time System Specification. Boston: Addison-Wesley.
Jorgensen, P. C. (2013). Software Testing: A Craftsman’s Approach, Third Edition. Boca Raton: CRC Press.
Kendall, K. &. (2014 ). Systems Analysis and Design, 9e. London, England: Pearson Education Inc. Publishing as pearson prentice hall.
Laplante, P. A., & Ovaska, . J. (2012). Real-Time Systems Design and Analysis: Tools for the Practitioner. Hoboken: John Wiley & Sons.
Litchfield, N. J., Berryman, K., & Thomas, R. (2013). Data dictionary: report produced in the context of the GEM. Lower Hutt: Institute of Geological and Nuclear Sciences.
Pressman, R. S. (2010). Software Engineering: A Practitioner’s Approach. New York City: McGraw-Hill Education.
Thalheim, B. ( 2013). Entity-Relationship Modeling: Foundations of Database Technology. Berlin/Heidelberg: Springer Science & Business Media.
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