Bubble Diagram Stratification

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Bubble Diagram Stratification

Rob ChapmanV1.4

March 30, 2006

Context Diagram Big Picture

Data Flow Diagrams

State Machine

Flow Chart

X DiagramMemory Map



This document describes a project annotation methodology which has evolved

from experience with all phases of many different projects. It is meant as a

central tool for documenting, brainstorming and describing projects from start to

finish and throughout the maintenance phase. The target audience is meant to be

all individuals involved in a project starting from project genesis with project

planners including managers and marketing people on through project builders

including designers, programmers, and technicians.

Copyright TimbreWorks Engineering 2000-2006

This work is licensed under a Creative Commons Attribution-NoDerivs 2.5

License.

http://creativecommons.org/licenses/by-nd/2.5/








Table of Contents

A. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Symbols

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Design Tips

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

General Notes

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

B. Summary of Stratification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Context Diagram

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Big Picture

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Data Flows Diagrams

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

State Diagrams

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Flow Charts

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

X-Diagrams

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Data Diagrams

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Memory Maps

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

C. Example Design: Super Cool Oven . . . . . . . . . . . . . . . . . . . . . . . . . 7

Context Diagram 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Big Picture 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Data Flow Diagram 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Data Flow Diagram 2

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

State Diagram 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

D. Other Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Memory Map 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Memory Map 2

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Flow Chart 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

State Diagram 2

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Data Flow Diagram 3

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Data Diagram 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

X Diagram 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Context Diagram and Big Picture Together

. . . . . . . . . . . . . . . . . . . . . . . . . . 16

E. Prototypes for Bubble diagramming . . . . . . . . . . . . . . . . . . . . . . . . 17



3

A. Introduction

Design documentation is most easily captured in a hierarchy of 2-dimensional

bubble and line diagramming strategies left over from the last millennium

including:

• Context Diagram (CD)• Big Picture (BP)

• Data flow Diagrams (DFD)

• State Diagrams (SD)

• Flowcharts (FC)

• X-Diagrams (XD)

• Data Diagrams (DD)

• Memory Maps (MM)

This stratification document describes and organizes these visual documentationtools in a methodology that may be used to enhance your ability to document

projects and designs. Not all projects will use all tools and not all tools are for all

projects. The size and complexity of a project will dictate the choice of tools

employed to lay out and describe the framework of the project and its factored

components. At some point, the diagram is implemented directly in the

programming language for the target or as a hardware description.

The highest level diagram, the Context Diagram

, is useful for communicating

outside of the engineering realm and serves as the first stake in the ground or the

anchor point for the design and product. It should change, if ever, rarely. The design

details are in the different sub-diagrams.

The Big Picture

is the next level “down” in the diagram hierarchy. It is used as a

focal point for all engineering designs, including hardware and software. The

sources and sinks are listed explicitly and if there is a storage or process relevant to

this level, it is shown as well. In a simple design, this can sometimes be the same as

the Context Diagram.

The next level includes a breakdown of the data flow using data flow diagrams

.This relates the data that is stored and moved in the design. The processes involved

can be related through state diagrams

, further sub-diagrams or with a flow chart

.

Memory maps

and data diagrams

can be used to describe the storage elements

and data flows. X diagrams

can be used to describe interactive data flows or

protocol scenarios between entities.



4

Symbols

This table lists some of the more common notational graphic elements and their

uses.

Design Tips

• apply proper layering and factoring (hierarchy and modularity)• sources and sinks in lower diagrams should be accounted for in the big picture

• stores are introduced at the layer they are shared

• factor with the proper level of detail

General Notes

• diagrams span software and hardware boundaries

Symbol Used In Used for

DFD

a

a. Note: CD and BP are simple DFDs.

an external source or sink of data flow

FC an action

DFD where data flow is stored

DFD where data flows are processed and created

FC start/entry and end/exit point

DFD flow of data from one of the above to one of the above

SD used to represent a state of context in a state diagram

SD represents the transitions in a state diagram

FC shows sequence of actions and decisions

FCa decision point in a flow chart where one of manypaths is taken

DFD can be used to indicate timing

source/

sink

store

process

flow

s tate

transition

decision

250 ms



5

B. Summary of Stratification

The diagrams are briefly summarized here:

Context Diagram

• highest level diagram

• just sources, sinks and a thing

• should never change

• not hardware/software specific

• effective for interacting with non-technical personal – not everyone is an

engineer

Big Picture

• next level down

• detailed sources and sinks

• can include high level storage

• not hardware/software specific

• highest full technical level

Data Flows Diagrams

• connections and processing of data flow between sources, sinks and storage

• show the connections and where the data will flow; direction also

• task bubbles can become state diagrams or click into another data flow diagram

• flows always start and end at a source, sink or store

• mappable to code; code should reflect the diagram structure

o

good tool for reverse engineering as well

• 3 different items: sinks/stores, process, storage

State Diagrams

• effective for showing complex control

• control under different conditions

• bubbles and lines showing events causing change of state

• states of flows

• should include idle state

• mappable to code; code should reflect the diagram structure

• use mealy/moore for shorthand or SDLs for multi-page documentation



6

Flow Charts

• for diagramming complex algorithms

• more of a low level tool to help document code sequences but not overall

program structure

• not required if code is factored into simple enough pieces

• maps well to the serial programming model prevalent in software design unlikehardware which is widely parallel

X-Diagrams

• for documenting protocol exchanges

• left and right angled down labeled arrows represent protocol unit exchanges

Data Diagrams

• boxes and lines can be used to detail complex data structures such as records• protocol data units

• relative placement of boxes indicates relationships in storage

Memory Maps

• used to show regions or blocks of memory relevant to a program



7

C. Example Design: Super Cool Oven

As an example of a design, we will design a device about the size of a microwave

that heats as well as cools. We will use thermal actuators to realize a thermal profile.

The heating is from a coil heater and goes up to 500

°

C. The cooling is from a

metered, fan blown liquid nitrogen nozzle which takes it down to -200

°

C.

Context Diagram 1

Design starts at the beginning with a context diagram.This is the highest level of the

design, the most often drawn diagram and the best understood by all disciplines

involved in any product discussion. The context diagram at its simplest and highest

level consists of a central machine connected to various sources and sinks.

Figure 1: Context diagram for Super Cool Oven showing the relevant external sinks and

sources that are connected to the design. It is common practice to lump comment elementstogether such as lights, LEDs, LCDs as just Display to simplify the diagram.

Big Picture 1

Clicking into the context diagram to add more detail, is the top level diagram of all

the other diagrams or, the Big Picture.This gives an engineering context and lists all

the relevant high level components in the design. Most of the time this is a further

breakdown of the external components of the context diagram and the possiblefactoring of the one machine into more than one machine, or the possible inclusion

of a high level storage device.

Thermal

ActuatorsSensors

Keypad Display

uper Cool

Oven

Alarm

PrinterRemote

Computer



8

Figure 2: The Big Picture for the Super Cool Oven design giving an engineering context anddetail.

Data Flow Diagram 1

The next level of factoring will be showing the highest level of data flow between

different sources and sinks. The Big Picture, clicks into a multitude of data flow

diagrams.

Figure 3: Data flow diagram for temperature from sensors to visual display and internalrepresentation

This data flow diagram reads in values from two different sensors, converts the

digital values to an analog temperatures for internal use and displays the

Cool

Heater

Fan

SampleSensor

Chamber

SensorDoor

Sensor

Keypad

LCD

Display

ChamberTemp

SampleTemp

PrinterComputer

Port

IndicatorLights

Super Cool

Oven

Audible

Alarm

Sample

Sensor

Chamber

Sensor

Chamber

Temp

Display

Sample

Temp

Display

Read and

display

current

temperatures



9

temperatures. A more detailed diagram showing some timing and factoring can be

seen in Figure 4

. The timing value is an optional feature added for convenience.

Figure 4: Detailed data flow from temperature sensors to display.

Data Flow Diagram 2

Figure 5: The data flow diagram for the keypad input.

The state diagram describes the different states that need to be defined for proper

keypad entry, and key repeating for the state diagram Scan Keypad in the DFD.

Sensor

A/Dmachine

sensor reading

convert

machine

temperature

Displayshower

machine

567 ms

~333ms

300 ms

345 ms

alarms

Alarm

keypadScan

Keypad

key repeats



10

State Diagram 1

Figure 6: Bubbles represent stable states while the lines represent a transition. Only onestate is active at a time.

Keypad

wait for a

while

key hit

debounce

timeout

key not hit

wait for

release

key hit

key not hit

repeat

t imeout



11

D. Other Examples

These are a collection of examples for the other diagramming tools.

Memory Map 1

This diagram shows the relationship between the memory addresses, memory

components and areas of memory where things map to:

External

Memory

Registers

Internal

RAM 8K

Internal

Flash

128K

0

0x0080.0000

0x00C0.0000

0x0001.FFFF

0x0080.1FFF

0x8000.0000

0xFFFF.FFFF

boot loader

MaxForth or

Application0x0000.4000

serial loader

ports



12

Memory Map 2

This one shows a more complex relationship with overlaid memory regions:

Flow Chart 1

This is a simple algorithm for using an analog to digital converter documented using

a flow chart. It shows the PCC

1

loop quite plainly:

1. Program counter capture (PCC) loops are where the program flow becomes mired in one spot of the program

waiting on a slower device.

MaxRTOS

CRF

Application

Flash

128K Bytes

BatRAM

32K Bytes

Static RAM

32K Bytes

16K programwindow

page

MaxForth

registers

peripherals 400

64K memory

space0

1

8 0

8 1

8 2

8 7

Page 87FFF

00 0

00 0

000

4K EEPROM

1000

get A/D

reading

initialize

A/D

request

channel 0

channel

0?not yet

display

reading

Done.



13

State Diagram 2

This state diagram is for the user interface on a handheld unit with a 2 line LCD and

a few labeled keys. The state bubbles are the actual LCD messages displayed in that

state and the key presses map to the transitions.

Data Flow Diagram 3

This is style of DFD is used to describe a protocol stack or a layered communication

architecture. It uses hierarchy to indicate layers of an overall system and the

communication paths that exist within that system and possibly other systems. In

2 second delay

startup

CalibrateClear

Clear

End

Load

Calibrate

Calibrate

Calibrate

Cancel



14

this example for SFAP (Small Frame Asynchronous Protocol1), the C programming

interface is added to the diagram beside the flows.

Data Diagram 1

This data diagram shows the relationships between data elements in an SFAP frame

1. http://www.ee.ualberta.ca/~rchapman/Cmpe401/pdfs/sfap.pdf

conversation

layer

SFAP layer

serial layer

SC1

send_payload()

tx_type()

t x ( )

SC1DRL

SC1SR1

SC1DRL

SC1SR1

sfap_query()

get_frame()

rx_query()

rx( )

encryption

layer

SFAP layer

serial layer

SC1

Sending communication stack Receiving communicat ion stack

sync length rest of bytes check-byteFAP frame 1st byte

packet



15

X Diagram 1

This X diagram example shows the exchange of secure packets and

acknowledgements in SFAP between two peers. Time flows down and peer one is

on the left while peer two is on the right. Actions taken by the peer are listed.

process, Ack and goto Packet 2 wait

packet 1

Ack

process, ack and goto Packet 1 wait

packet 2

Ack



16

Context Diagram and Big Picture Together

Sometimes it is useful to merge diagrams together as in this case of a seismic

instrument, although probably more difficult to maintain:

Microphone

Battery

Timebase

Computer

Printer

Display

Seismograph

Charge

Seismicdata

Acousticdata

Timeevent

Report

Key

Displayinfo

Request

Record

Geophone

Data Capture

Data Display

Data Transfer

Life Monitor

Keypanel



Source or Sink

Process

State

Store

Decision

time

E. Prototypes for Bubble diagrammingCopy these into your document or use your diagramming tool to

create them and use them to build up your bubble diagrams.

Documents

Bubble Diagram Stratification