Why Use SysML?Eric A. BarnhartEric A. Barnhart

Systems Engineering

Systems Engineering is an interdisciplinary approach and means to enable the realization of successful systems. It focuses on defining customer needs and required functionality early in the development cycle, documenting requirements, then proceeding with design synthesis and system validation while considering the complete problem.

Communications!

Time Delay!

It’s all about the…

communication!

Communications and Learning

• Verbal-Linguistic– Sharing words, writings, documents– Why are we stuck here?

• Logical-Mathematical– Equations, drawings, MatLab models– Engineering discipline

• Visual-Spatial– Pictures, charts, drawings– Approximately 30% of people!

• Other methods too…

What is SysML?

• SysML is a graphical language

• SysML is a method for communications• SysML emphasizes the SE domain• SysML is NOT a specific tool or

methodology

Main Entry: lan·guage       

Pronunciation: \ˈlaŋ-gwij, -wij\

Function: noun

1 … (2): a systematic means of communicating ideas or feelings by the use of conventionalized signs, sounds, gestures, or marks having understood meanings (3): … (4): … (5): a formal system of signs and symbols (as FORTRAN or a calculus in logic) including rules for the formation and transformation of admissible expressions

SysML Relationship To UML

UML 2.0

SysML

New Diagrams: Parametric Constraint, Requirement

Common Diagrams: Activity, Block Definition (UML2::Class), Internal Block (UML2::Composite Structure), Package, Sequence, State Machine, Use Case

For more info…www.sysml.org

SysML Trivia

• SysML is a UML profile– Inherits the mature UML notation– Inherits UML “bloat”– Compatible with UML

• SysML is SE domain specific, UML is general purpose

• SysML abandons some of the software-centric aspects of UML

Our typical form of communications

Nitrogen

Gas

Bottle

“The System”

The dreaded “block

diagram”

Simplified Block Diagram

A B

Track Target Report PositionOrder of

operation?

Simulation FederationRelationship?

RT Clock ExecutiveInterface?

What does a block diagram mean?????

A little better?

Assembly

Assembly “S”

ExIPI

Nitrogen

Gas

Bottle

Thingy

Nitro

Doodad Dadood

Pete’s Part

A, B, C, D

“The System”

M

Point

Alpha

Confabulator

Widget

Gizmo

F

Try This Syntax

A component

Ports – controlled points of interface(with optional direction)

Frame

A frame to group things

An Interface entity - Required

An Interface entity - Supplied

Better yet

“The System”

Assembly “S”

Nitrogen Gas

Bottle

Nitro

Point

Alpha

Widget

Confabulator

Gizmo

Thingy

Doodad

Dadood

Parametrics

P1

P2

P3

Nitrogen Gas

Bottle

Pete’s Part

M

SoftwareProgram 1

Software

Program 2ExIPI

Even Better with Full Context

LOS Stabilization

IR Sensor

Nitrogen Gas

Bottle

Nitrogen Bottle

2 Axis Gimbal

AngleTransducer

Power Amp

Reference Wheel

Torque Motors

FPGA

ADC

DAC

Parametrics

P1

P2

P3

Nitrogen Gas

Bottle

Mission Processor

IMU

SoftwareProgram 1

Software

OFPExternal IR

Photon Input

massmotion

coolant flow

physical

pitch

yaw

physical physical

pitch drive

yaw drive

zero point

Compare and Contrast

LOS Stabilization

IR Sensor

Nitrogen Gas

Bottle

Nitrogen Bottle

2 Axis Gimbal

AngleTransducer

Power Amp

Reference Wheel

Torque Motors

FPGA

ADC

DAC

Parametrics

P1

P2

P3

Nitrogen Gas

Bottle

Mission Processor

IMU

SoftwareProgram 1

Software

OFPExternal IR

Photon Input

massmotion

coolant flow

physical

pitch

yaw

physical physical

pitch drive

yaw drive

zero point

Assembly

Assembly “S”

ExIPI

Nitrogen

Gas

Bottle

Thingy

Nitro

Doodad Dadood

Pete’s Part

A, B, C, D

“The System”

M

Point

Alpha

Confabulator

Widget

Gizmo

F

Block diagram with random or inconsistent meaning to symbols

Component diagram with well-defined syntax and grammar

Communications

The engineer must use a consistent, well-defined, and well-understood language to communicate the requirements and design to other engineers, otherwise the product will founder, fail, or be a disaster.

For the systems engineer, that language is currently SysML.

Axiom

Ένα πρόβλημα με καλη σαφήνεια είναι

μισό λυμένω

Translations courtesy Haratini E. Andre

Communicating Well

• In order to communicate you must speak a common language

• You must share the problem definition– Across cultures– Across space– Across TIME

“A problem well-defined is half solved.” Lou Cohen

Matching the Language to the Problem• Verbal-linguistic methods for system definition

– Writing specs, ICDs, SRSs, etc.

• Logical-mathematical methods for system definition– Models, MatLab files

• Visual-spatial methods for system definition– Pictures– Drawings– Charts

SysML is a suitable language, iff you model your system. If you

don’t, then it won’t work.

SysML is a suitable language, iff you model your system. If you

don’t, then it won’t work.

Models too!}

Is there a problem?

Όλα είναι ελληνικά σε μένα

Translations courtesy Haratini E. Andre

You have to speak the modeling language, otherwise…

(It’s all Greek to me)

Prerequisites

1. You must be able to use the language2. You must model your system as a standard

practice3. “Speak” the language

• Learn UML, SysML• Practice, practice, practice

4. Your boss must recognize the language• Never leave your boss in the dark• Never make your boss look stupid

5. Your boss must understand WHY you speak the language

6. Your customers (internal and external) must understand the language and the models

INCOSE Orlando Presents:

SysML Tutorial, June 8th

By Sandy FriedenthalLockheed Martin

INCOSE Orlando Presents:

SysML Tutorial, June 8th

By Sandy FriedenthalLockheed Martin

Why model?

Drawing Modeldepiction information

System

describes

1+

1By themselves, drawings can have dubious value

DefineRequirements

Design System Implement Integrate

The models they depict have enormous value to the SE

process

RequirementsModel

Got Models? – Operational Concepts

• Do you do analyze operational concepts?

Copilot /Gunner

Track Target

Select Track Mode

Drive Turret Manually

Autotrack Image

Scan by Pattern<<extends>>

<<extends>>

<<extends>>

<<extends>>

Sample Use Case Diagram

Got Models? - Requirements

• Do you model requirements and their relationships?

Sample Requirements Diagram

Got Models? – Functional Decomposition• Do you do functional

decomposition? (DoDAF SV-4)

Select Track Source

Process Rate CommandsProcess Position Commands

Drive Gimbals

Stabilize LOS (Az/El)

Apply Drift Cooefficients andScale Factors

Report LOS Angular Data

Enable/Disable Deroll

Stabilize Image Roll Axis

Get Internal Tracker Inputs

Follow Internal Tracker Follow External Source

Includes a) Follow Weapon, b) Cue to Compass Relative Position,

c) Cue to Geolocation Position

Select Auto / ManualDrift Compensation

Calculate Drift Coefficientsand Scale Factors

Get IMU Rates

Servo Loops

Drift Compensation Calculation LOS Control

Sample Activity Diagram

Got Models? – States & Modes• Do you analyze states/modes?

(DoDAF SV10b)

POWER APPLIED [ powerIsStable]

SELF TEST FAILED / STORE FAILURE DATA

TEMP REACHES OPT / ASSERT READY

ENABLE CMD RCVDOPTIONS SET CMD( ) [ options enabled ] / SET OPTION

OFF COMMAND RCVD / STORE DATA

TEMP FAULT

EXECUTE COMMAND[ safety confirmed ]

DISABLE CMD RCVD

Off Mode

Warmup Mode

TEMP FAULT

OFF COMMAND RCVD / STORE DATA

OFF COMMAND RCVD / STORE DATA

OFF COMMAND RCVD / STORE DATA

Failure Mode

Standby Mode

Ready Mode

Fire Mode

EXECUTION COMPLETED

entry: emit 3 pulses

entry: Assert Not Ready

Sample State Diagram

Got Models? – Event Traces

• Do you trace events? (DoDAF SV-10c)

<<device>>ChangeDispenserCredit

<<device>>AlphaNumericDisplay

<<device>>ScrewActuatorChute

<<device>>Keypad

EnterLocation DisplayMessage( code )

BuyProduct( selection )

GetPrice( selection )

CompareToPrice

DisplayMessage( error )

-end-

DispenseProduct( selection )Turn

CalculateChange

DispenseAmount

resetAmount

<<device>>M.A.U

AcceptFunds

Sample Sequence Diagram

Got Models? - Deployment

• Do you deploy components onto processors?

Sample Deployment Diagram(borrowed from UML)

Got Models? - Parametrics

• Do you create parametric models?

filleted_tapered_i_section

flange_fillet_radius

area

flange_thickness

web_height

flange_taper_thickness

flange_taper_angle

flange_base_thickness

flange_width

web_thickness

total_height

flange_fillet_radius

area

flange_thickness

web_height

flange_taper_thickness

flange_taper_angle

flange_base_thickness

flange_width

web_thickness

total_height

tapered_i_section

flange_taper_thickness

flange_taper_angle

flange_base_thickness

flange_width

web_thickness

total_height

«paramConstraint»: relation13

«paramConstraint»: relation14

total_height

flange_width

flange_thickness

web_thickness

area

web_height

flange_taper_thickness

flange_taper_angle

flange_base_thickness

flange_width

web_thickness

total_height

«paramConstraint»: relation13

«paramConstraint»: relation14

total_height

flange_width

flange_thickness

web_thickness

area

web_height

basic_i_section

«paramConstraint»: relation13

area

flange_width

flange_thickness

web_thickness

web_height

total_height

«paramConstraint»: relation13

area

flange_width

flange_thickness

web_thickness

web_height

total_height

«paramConstraint»relation8

«paramConstraint»relation9

«paramConstraint»relation10

«paramConstraint»relation11

«paramConstraint»relation12

«paramConstraint»relation13

«paramConstraint»relation14

«paramConstraint»relation15

«paramConstraint»relation16

«paramConstraint»relation17

asm : Cross Section Assembly Diagram

Sample Parametrics Diagrams

SysML Drawing SummarySYSML DIAGRAM PURPOSE UML ANALOG

Activity diagram Show system behavior as control and data flows. Useful for functional analysis. Compare Extended Functional Flow Block diagrams (EFFBDs), already commonly used among systems engineers. 

Activity diagram

Block Definition diagram

Show system structure as components along with their properties, operations and relationships. Useful for system analysis and design.

Class diagram

Internal Block diagram

Show the internal structures of components, including their parts and connectors. Useful for system analysis and design.

Composite Structure diagram

Package diagram Show how a model is organized into packages, views and viewpoints. Useful for model management.

Package diagram

Parametric diagram Show parametric constraints between structural elements. Useful for performance and quantitative analysis.

N/A

Requirement diagram

Show system requirements and their relationships with other elements. Useful for requirements engineering.

N/A

SysML Drawing Summary - cont.

Sequence diagram

Show system behavior as interactions between system components. Useful for system analysis and design.

Sequence diagram

State Machine diagram

Show system behavior as sequences of states that a component or interaction experience in response to events. Useful for system design and simulation/code generation.

State Machine diagram

Use Case diagram

Show system functional requirements as transactions that are meaningful to system users. Useful for specifying functional requirements. (Note potential overlap with Requirement diagrams.)

Use Case diagram

Allocation tables*  *dynamically derived tables, not really a diagram type

Show various kinds of allocations (e.g., requirement allocation, functional allocation, structural allocation). Useful for  facilitating automated verification and validation (V&V) and gap analysis.

N/A

UML 2.0 Component, Communications, Object, Deployment, Interaction and Timing diagrams have not been included in SysML

Leaving SysML at Home

• Don’t bother with SysML if..– your process is centered on writing

nothing but textual specifications– you don’t model your systems– your management won’t read SysML

diagrams– your customer won’t read SysML– all you want to do is say you’re using

it

Bringing SysML to Work

• Selling SysML to systems engineers

Preaching to the Choir

Bringing SysML to S/W Engineers

• Selling points– They’re probably already using UML– “now we can communicate better”

Bringing SysML to Management

• Selling Points– Better communications– Reduced errors– “Easy to learn”

• Break them in slowly– Interface to S/W– Improved integration– Solid, proven technology– Customers are asking for it– Competitors are using it

• DON’T ask for a $20K tool up front– Use SysML manually first, buy the tool later

• Some managers just don’t get it

• Chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken chicken

Bringing SysML to EEs

EE’s generally won’t care(neither will ME’s)

Getting Started – One Idea

• Use the language any way you can– Visio, PowerPoint, etc.

• Insinuate the language into existing work products– Drawings start appearing in specs– Control the document = control the drawing

inside it– Do the analysis as part of the effort to write

the CDRL

• Make the managers want it• Buy the tool after SysML is part of your

process

Why SysML?

• Standardized communications- across space- across time

• Improve life-cycle management• Capture the artifacts of systems

engineering

• Eliminate dreaded Block Diagrams