Interface Design
Interface design of the system needs to stabilize very early in the development process in order to begin creating the stubbed-out function tests that call the API functions that are part of the system's external interface (V-Development).
Note: At this point in the software development process flow, many of the examples will be scoped to a particular part of the overall system under development. Interface artifacts and detailed design artifacts are going to contain a large amount of content and would likely negatively affect the comprehensibility of the content published on this website. The purpose of these examples is to provide additional information on what constitutes a software development process as opposed to providing a complete set of system development artifacts.
Interfaces can be specified in a variety of ways. The specification can be text only, a graphical model such as a UML class diagram, or a combination of text and graphics. I prefer using a combination of text and graphics so that data characteristics, syntax, and semantics can be specified using the most appropriate means of conveyance.
On this page, I will provide examples of the following interface specification artifacts:
- Component Interface / Interconnection View Diagram
- UML Class Diagram
- Interface Specification Document
At the end of this web page, the V-Model is again referenced with respect to how it applies to interface design.
Component Interface / Interconnection View Diagram
The following diagram is a high-level component-and-connector view diagram that represents interfaces as annotated ports. This diagram is similar to a data-flow diagram and is referred to as a Component Interface / Interconnection View diagram. It models the microwave oven example.
Component Interface / Interconnection View diagram
Data Dictionary:
|
Term |
Description |
Type |
Requirements
Trace |
|
Beeper |
Beeper
component that encapsulates beeper functionality. |
Component |
|
|
Beeper
Signal-out |
Output
from the Output Processing System component that contains signals to
the beeper device. |
Output
Data |
|
|
Command
Processing System |
Controller
component that encapsulates controller functionality. |
Component |
|
|
Cooking
Function Description |
Cooking
function description data that flows from the Command Processing System
component to the Oven Control System component. This data identifies
the cooking function selected. |
Data
Flow |
|
|
Cooking
Function Desc-in |
Oven
Control System input cooking data. |
Input
Data |
|
|
Cooking
Function Desc-out |
Command
Processing System component output cooking data. |
Output
Data |
|
|
Display |
Display
component that encapsulates display functionality. |
Component |
F3, F4, F4.1.1, F4.1.2, F4.1.3, F4.1.4, F4.1.5, F4.1.6, F4.1.7, F4.1.8, F4.1.9, F4.2.1, F4.2.6, F4.2.7, F4.3.1, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.4, F4.4.5, F4.4.6, F4.5.5, F4.5.7, F4.5.8, F5, F6 |
|
Display
Desc |
Data
that flows from the Output Processing System component to the Display
component that contains signals to the display device. |
Data
Flow |
F3, F4, F4.1.1, F4.1.2, F4.1.3, F4.1.4, F4.1.5, F4.1.6, F4.1.7, F4.1.8, F4.1.9, F4.2.1, F4.2.6, F4.2.7, F4.3.1, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.4, F4.4.5, F4.4.6, F4.5.5, F4.5.7, F4.5.8, F5, F6 |
|
Display
Desc-out |
Output
from the Output Processing System component that contains signals to
the display device. |
Output
Data |
F3, F4, F4.1.1, F4.1.2, F4.1.3, F4.1.4, F4.1.5, F4.1.6, F4.1.7, F4.1.8, F4.1.9, F4.2.1, F4.2.6, F4.2.7, F4.3.1, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.4, F4.4.5, F4.4.6, F4.5.5, F4.5.7, F4.5.8, F5, F6 |
|
Door |
Door
component that encapsulates door functionality. |
Component |
|
|
Door
Sensor |
Input
data to theCommand Processing System (Controller) component that
contains door status data. |
Input
Data |
|
|
Door
Status Data |
Data
that flows from the door latch sensor to the Command Processing System
(Controller) component. |
Data
Flow |
|
|
Generator
Control-out |
Oven
Control System component output that contains the control codes for the
generator. |
Output
Data |
|
|
Input
Data Stream |
Data
that flows from the Keypad component to the Command Processing System
(Controller) component. This data contains keycode
data from the keypad. |
Data
Flow |
|
|
Keypad |
Keypad
component that encapsulates keypad functionality. |
Component |
|
|
Keypad-in |
Input
data to the Command Processing System (Controller) component that
contains keycode
data from the keypad. |
Input
Data |
|
|
Microwave
Generator |
Microwave
Generator (cavity magnetron) component that encapsulates generator
functionality. |
Component |
|
|
On/Off
and Power Level |
Data
that flows from the Oven Control System component to the Microwave
Generator component. This data that contains the current status and
power level of the generator. |
Data
Flow |
F4.3.1, F4.3.2, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.6, F4.5.1, F4.5.2, F4.5.6, F4.5.7, F4.5.9, F4.5.10, F4.5.12 |
|
On /
Off Signal |
Data
that flows from the Output Processing System component to the Beeper
component. This data contains the status of the beeper device. |
Data
Flow |
|
|
Output
Processing System |
Output
Processing System component that encapsulates output processing system
functionality. |
Component |
F3, F4, F4.1.1, F4.1.2, F4.1.3, F4.1.4, F4.1.5, F4.1.6, F4.1.7, F4.1.8, F4.1.9, F4.2.1, F4.2.6, F4.2.7, F4.3.1, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.4, F4.4.5, F4.4.6, F4.5.5, F4.5.7, F4.5.8, F5, F6 |
|
Oven
Control System |
Oven
Control System component that encapsulates oven control functionality. |
Component |
|
|
Process-Desc |
Process-related
data that flows from the Command Processing System component to the
Output Processing System component. |
Data
Flow |
F3, F4, F4.1.1, F4.1.2, F4.1.3, F4.1.4, F4.1.5, F4.1.6, F4.1.7, F4.1.8, F4.1.9, F4.2.1, F4.2.6, F4.2.7, F4.3.1, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.4, F4.4.5, F4.4.6, F4.5.5, F4.5.7, F4.5.8, F5, F6 |
|
Process-Desc-In |
Input
data to the Output Processing System component that contains cooking
process-related data. |
Input
Data |
F3, F4, F4.1.1, F4.1.2, F4.1.3, F4.1.4, F4.1.5, F4.1.6, F4.1.7, F4.1.8, F4.1.9, F4.2.1, F4.2.6, F4.2.7, F4.3.1, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.4, F4.4.5, F4.4.6, F4.5.5, F4.5.7, F4.5.8, F5, F6 |
|
Process-Desc-Out |
Output
from the Command Processing System component that contains cooking
process-related data. |
Output
Data |
F3, F4, F4.1.1, F4.1.2, F4.1.3, F4.1.4, F4.1.5, F4.1.6, F4.1.7, F4.1.8, F4.1.9, F4.2.1, F4.2.6, F4.2.7, F4.3.1, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.4, F4.4.5, F4.4.6, F4.5.5, F4.5.7, F4.5.8, F5, F6 |
UML Class Diagram
Data Dictionary:
|
Term |
Description |
Type |
Requirements
Trace |
|
amPm |
Contains
the time-of-day integer antemeridiem / postmeridiem value. Attribute of
Clock class. |
int |
|
|
autoCookDuration |
Contains
the time period value for the amount of time to cook the item.
Attribute of AutoCookPresetKeyImpl. |
int |
|
|
AutoCookImpl |
This
class contains all of the AutoCookPresetKeyImpl objects as attributes
and realizes the AutoCookInterface |
Class |
|
|
AutoCookInterface |
Interface
for the auto-cook functionality. Contains the various preset keys
available for the microwave oven. |
Interface |
|
|
AutoCookPresetKeyImpl |
Manufacturer-defined
presets for heating common food items. Implementation class that
realizes the AutoCookPresetKeyInteface. |
Class |
|
|
AutoCookPresetKeyInterface |
Interface
for auto-cook preset keys. |
Interface |
|
|
autoCookPowerLevel |
Contains
the power level value for the power level at which to cook the item.
Attribute of AutoCookPresetKeyImpl. |
int |
|
|
AutoDefrostKeyImpl |
Derived
from the AutoCookPresetKeyImpl class. Key used to set power level and
time for defrosting frozen food items. |
Class |
|
|
Interface
for the auto-defrost functionality. |
Interface |
||
|
beverage |
Attribute
of the AutoCookImpl class. The beverage auto-cook preset key
automatically sets the heating time and power level for hot beverages. |
AutoCookPresetKeyImpl |
|
|
beeperDuration |
Contains
the integer beeper duration value. Attribute of Timer class. |
int |
|
|
Clock |
Class
that realizes ClockInterface and implements the clock key that is used
in conjunction with numeric keys to set the clock. |
Class |
|
|
Interface
for the clock functionality. |
Interface |
||
|
DoorImpl |
Realizes
the DoorInterface. Implements door latch sensor signal-handling
capabilities. |
Class |
|
|
DoorInterface |
Interface
for the door latch sensor input. |
Interface |
|
|
doorStatus |
Attribute
of the DoorImpl class. Status input from door latch sensor. |
byte |
|
|
failure |
Attribute
of HardwareSignalImpl class. Failure indication from hardware component
(if failure occurs). |
byte |
|
|
freshVeg |
Attribute
of the AutoCookImpl class. The freshVeg auto-cook preset key
automatically sets the heating time and power level for fresh
vegetables. |
AutoCookPresetKeyImpl |
|
|
frozenEntrée |
Attribute
of the AutoCookImpl class. The frozenEntree auto-cook preset key
automatically sets the heating time and power level for frozen entrees. |
AutoCookPresetKeyImpl |
|
|
FunctionImpl |
Class
that realizes the FunctionInterface and contains the function key
objects as class attributes. Allows execution of functions such as
PowerLevel, Program, AutoDefrost, Stop/Clear, Start, Clock, and Timer. |
Class |
|
|
FunctionInterface |
Interface
for the function key functionality of the microwave oven. |
Interface |
|
|
FunctionKeyImpl |
Class
that realizes the FunctionKeyInterface and provides basic function key
functionality. |
Class |
|
|
functionType |
Contains
the type of function. An attribute of the FunctionKeyImpl class. |
byte |
|
|
getAmPm |
Getter
method for AM / PM value. Defined in Clock class. |
operation |
|
|
getAutoCookDuration |
Getter
method for auto-cook duration value. Defined in AutoCookPresetKeyImpl
class. |
operation |
|
|
getAutoCookInterface |
Getter
method for auto-cook interface implementation object that contains all
preset functionality. Defined in Keypad class. |
operation |
|
|
getAutoCookPowerLevel |
Getter
method for auto-cook power level value. Defined in
AutoCookPresetKeyImpl class. |
operation |
|
|
getAutoDefrost |
Getter
method for auto-defrost implementation object. Defined in AutoCookImpl
class. |
operation |
|
|
getBeeperDuration |
Getter
method for beeper duration value. Defined in Timer class. |
operation |
|
|
getBeveragePreset |
Getter
method for the beverage preset implementation object. Defined in
AutoCookImpl class. |
operation |
|
|
getClock |
Getter
method for clock implementation object. Defined in FunctionImpl class. |
operation |
|
|
getDoorStatus |
Getter
method for door status value (open / closed). Defined in DoorImpl class. |
operation |
|
|
getFailure |
Getter
method for hardware failure value. |
operation |
|
|
getFunctionType |
Getter
method for active function mode value. Defined in FunctionKeyImpl class. |
operation |
|
|
getFunctionInterface |
Getter
method for function interface implementation object that contains all
oven functions. Defined in Keypad class. |
operation |
|
|
getHour |
Getter
method for current clock hour value. Defined in Clock class. |
operation |
|
|
getInputType |
Getter
method for current type of input value. Defined in InputInterfaceImpl
class. |
operation |
|
|
getKeyArray |
Getter
method for value sequence of numeric keys pressed. Defined in
NumericImpl class. |
operation |
|
|
getKeyType |
Getter
method for type of key pressed value. Defined in KeyImpl class. |
operation |
|
|
getKeyValue |
Getter
method for numeric value of numeric key pressed. Defined in
NumericKeyImpl class. |
operation |
|
|
getLevel |
Getter
method for current power level value selected. Defined in PowerLevel
class. |
operation |
F4.3.1,
F4.3.2,
F4.3.3,
F4.4.1,
F4.4.2,
F4.4.3,
F4.4.6,
F4.5.1,
F4.5.2 |
|
getMinute |
Getter
method for current minute value of the clock. Defined in Clock class. |
operation |
|
|
getMinutes |
Getter
method for current minutes value of the timer. Defined in Timer class. |
operation |
|
|
getNumericInterface |
Getter
method for auto-cook interface implementation object that contains all
preset functionality. Defined in Keypad class. |
operation |
|
|
getPizzaPreset |
Getter
method for the pizza preset implementation object. Defined in
AutoCookImpl class. |
operation |
|
|
getPopcornPreset |
Getter
method for the popcorn preset implementation object. Defined in
AutoCookImpl class. |
operation |
|
|
getPotatoPreset |
Getter
method for the potato preset implementation object. Defined in
AutoCookImpl class. |
operation |
|
|
getPowerLevel |
Getter
method for power level implementation object. Defined in FunctionImpl
class. |
operation |
F4.3.1, F4.3.2, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.6, F4.5.1, F4.5.2 |
|
getPressed |
Getter
method for key-pressed status attribute. Defined in KeyImpl class. |
operation |
|
|
getRemaining |
Getter
method for remaining timer duration value. Defined in Timer class. |
operation |
|
|
getSeconds |
Getter
method for current seconds value of timer. Defined in Timer class. |
operation |
|
|
getTimeOfDay |
Getter
method for current time of day value. Defined in Clock class. |
operation |
|
|
getTimer |
Getter
method for timer implementation object. Defined in FunctionImpl class. |
operation |
|
|
getTypeOfMeat |
Getter
method for type of meat selected value. Defined in AutoDefrostKeyImpl
class. |
operation |
|
|
getWeight |
Getter
method for weight of meat value. Defined in AutoDefrostKeyImpl class. |
operation |
|
|
handleHardwareSignal |
Signal
handler method that is called when a hardware component sends a signal.
Defined in HardwareSignalImpl class. |
operation |
|
|
handlePressEvent |
Event
handler method that is called when a key is pressed by the user.
Defined in KeyImpl class. |
operation |
|
|
HardwareSignalImpl |
Class
that realizes the HardwareSignalInterface and provides the capability
to receive hardware component signals as input data. |
Class |
|
|
HardwareSignalInterface |
Interface
for the hardware signal handling functionality which provides
communication with hardware components. |
Interface |
|
|
hour |
Contains
the current clock (time-of-day) integer hour value. Attribute of Clock
class. |
int |
|
|
InputInterfaceImpl |
Parent
input class to the following derived classes: DoorImpl,
HardwareSignalImpl, KeyImpl. |
Class |
|
|
inputType |
Contains
type of interface data. Attribute of InputInterfaceImpl class. |
Attribute |
|
|
KeyImpl |
Class
that realizes the KeyInterface and provides the capability to process
key-press events as input data. |
Class |
|
|
KeyInterface |
Interface
for key-press event functionality which assists in communicating with
the keypad. |
Interface |
|
|
Keypad |
Implementation
class that is composed of one object of each of the following classes:
AutoCookImpl, NumericImpl, FunctionImpl. This class contains all keypad
functionality. |
Class |
|
|
keyType |
Contains
the type of key. Attribute of KeyImpl class. |
byte |
|
|
keyValue |
Contains
the integer value of the numeric key. Attribute of NumericKeyImpl class. |
int |
|
|
level |
Contains
the integer value of the selected level of power. Attribute of
PowerLevel class. |
int |
F4.3.1, F4.3.2, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.6, F4.5.1, F4.5.2 |
|
minute |
Contains
the time-of-day integer minute value. Attribute of Clock class. |
int |
|
|
minutes |
Contains
the timer integer minutes value that specifies the current number of
minutes. Attribute of Timer class. |
int |
|
|
NumericInterface |
Interface
for the numeric key functionality. This interface contains all of the
NumericKeyImpl objects. |
Interface |
|
|
NumericKeyImpl |
Keys
are numbered 0-9 for manually entering numeric values used for setting
the clock, the timer, the power level, and the cooking time.
Implementation class that realizes the NumericKeyInteface. |
Class |
|
|
NumericKeyInterface |
Interface
for the numeric key functionality. |
Interface |
|
|
popcorn |
Attribute
of the AutoCookImpl class. The popcorn auto-cook preset key
automatically sets the heating time and power level for microwave
popcorn. |
AutoCookPresetKeyImpl |
|
|
potato |
Attribute
of the AutoCookImpl class. The popcorn auto-cook preset key
automatically sets the heating time and power level for one potato. |
AutoCookPresetKeyImpl |
|
|
PowerLevel |
Class
that realizes PowerLevelInterface and implements the power level key
that is used in conjunction with numeric keys to set the power level. |
Class |
F4.3.1, F4.3.2, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.6, F4.5.1, F4.5.2 |
|
PowerLevelInterface |
Interface
for power level functionality. |
Interface |
F4.3.1, F4.3.2, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.6, F4.5.1, F4.5.2 |
|
pressed |
Contains
the pressed status of key. Attribute of KeyImpl class. |
boolean |
|
|
seconds |
Contains
the timer integer seconds value that specifies the current number of
seconds of timer duration. Attribute of Timer class. |
int |
|
|
sendPowerSignal |
Method
of PowerLevel class that sends the power level signal to the cooker
device. |
operation |
F4.3.1, F4.3.2, F4.3.3, F4.4.1, F4.4.2, F4.4.3, F4.4.6, F4.5.1, F4.5.2 |
|
sendClockBytes |
Method
of Clock class that sends the clock setting bytes to the clock device. |
operation |
|
|
sendTimerBytes |
Method
of Timer class that sends the timer setting bytes to the timer device. |
operation |
|
|
Timer |
Class
that realizes TimerInterface and implements the timer key that is used
in conjunction with numeric keys to set the timer. |
Class |
|
|
TimerInterface |
Interface
for timer functionality. |
Interface |
|
|
typeOfMeat |
Type of
meat to be defrosted. Attribute of AutoDefrostKeyImpl class. |
int |
|
|
weight |
Weight
of meat to be defrosted. Attribute of AutoDefrostKeyImpl class. |
int |
Interface Specification Document
1 Interface Definition
Note: Parameters are listed by Name, Type, and In/Out/In-Out to indicate if they are read-only (In), write-to (Out), or read-and-write (In-Out). Types that are listed in all caps are variable types that have been defined for this specific application.
1.2 Clock Function
Parameters:
Clock_start_time, TIME_H_M, In
Start, ENUMERATION, In
Current_time_of_day, TIME_H_M, Out
The clock function receives an initial time of day setting from the operator then increments the current time value once per minute. Once a minute the current time value is output to the Display Time function for display.
Link to detailed interface specification for the Clock Function:
Interface Specification for the Clock Inteface of the Microwave Oven Example
1.3 Timer
Function
Parameters:
Initial_timer_value, TIME_M_S, In
Start, ENUMERATION, In
Stop_Clear_Interrupt, ENUMERATION, In
Beeper_duration_time, Integer, Out
Current_timer_value, TIME_M_S, Out
This function receives an initial timer value that was input from the operator then counts down the time until it reaches zero. As the timer counts down the current time is sent once per second to the Display Time function. Once the timer reaches zero a value is sent to the Beeper function indicating the length of time that the beeper should sound. If a Stop interrupt signal is received during the count down, the time is halted until either a Stop/Clear signal is received (to cancel the timer countdown) or a Start signal is received (to continue the timer countdown).
1.4 Auto
Cook Presets Function
Preset_selected, ENUMERATION, In
Cooking_time, TIME_M_S, Out
Power_level, Integer, Out
This function receives an input indicating which operator preset button was pressed. The predefined power level and cooking time associated with that preset button are looked up in the Auto Cook Preset power and cooking time database. The power and cooking time values are output to the Cooking Control
Function.
1.5
Auto
Defrost Function
Meat_type, MEAT_TYPE, In
Weight_of_meat, Float, In
Cooking_time, TIME_M_S, Out
Power_level, Integer, Out
This function receives a type of meat and the weight of the meat from the Monitor and Process Inputs function. Based on the type of meat and the weight of meat the function determines the correct values for power level and cooking time. The power level and cooking time values are then output to the Cooking Control Function.
Link to detailed interface specification for the Auto-Defrost Function:
Interface Specification for the Auto-Defrost Key Inteface of the Microwave Oven Example
V-Model Diagram
As illustrated in the below V-Model diagram, at this point in the software development process, creation of system integration test plans and unit test plans should begin. System integration test plans should focus on testing the syntax and semantics of the interfaces that have been defined. Unit tests must focus on the implementation details of the implementations that realize those interfaces.