Lecture 1: Introduction

Lecture 1 – Introduction Prof. Dov Dori

Methodologies in Systems Development –

Model-Based Systems Engineering097230 – Spring 2011

Lecturer: Prof. Dov Dori TIDES Pedagogical Advisors:

The William Davidson Facultyof Industrial Engineering and Management

Lecture 1: Introduction

Lecture 1 – Introduction Prof. Dov Dori

Content

2

Course objectives Systems Engineering (SE) definitions Benefits of SE A Universal Ontology for SE System, Function, and Concept

Lecture 1 – Introduction Prof. Dov Dori3

Course Objectives Study about systems and their development:

How to analyze systems How to model systems How to architect systems How to design systems How to test systems

This is a course about How to think, not What to think

Focus: Model-Based Systems Engineering –MBSE Via a critical review of OPM Second Edition book


Systems Engineering Defined

INCOSE – International Council on Systems Engineering Systems Engineering Handbook


What is Systems Engineering ?

Systems Engineering (SE) is a comprehensive approach to the development of any complex, multidisciplinary system.

The quality of the system resulting from SE impacts the cost and value of the entire project.


More Systems Engineering Definitions

“The top level process of engineering a system to meet overall requirements.”www.tso.co.uk/demo/itil2/cd/content/ss/ss_apdx_a_02.htm

“The application of engineering to solutions of a complete problem in its full environment by systematic assembly and matching of parts in the context of the lifetime use of the system.”www.ichnet.org/glossary.htm

Engineering Systems At MIThttp://techtv.mit.edu/collections/esd/videos/9379-the-engineering-systems-division-at-mit

http://www.tso.co.uk/demo/itil2/cd/content/ss/ss_apdx_a_02.htm

http://www.ichnet.org/glossary.htm

http://techtv.mit.edu/collections/esd/videos/9379-the-engineering-systems-division-at-mit




Yet another SE Definition “Systems engineering is the branch of engineering concerned with the development of large and complex systems.Systems engineering focuses on the real-world goals for, services provided by, and constraints on such systems; the precise specification of system structure and behavior, and the implementation of these specifications; the activities required in order to develop an assurance that the specifications and real-world goals have been met; the evolution of such systems over time and across system families. It is also concerned with the processes, methods and tools for the development of systems in an economic and timely manner.”http://www.mssl.ucl.ac.uk/syseng/pages/sedef.html

http://www.mssl.ucl.ac.uk/syseng/pages/sedef.html


Engineering Systems At MIT

Related to systems engineering, which is an important profession and practice, engineering systems is a field of scholarship that includes systems engineering as well as a broader set of disciplines. Engineering systems has an added focus on social, environmental, technological, and political contexts.

Watch some of the 7 min. video:






SE and Engineering Systems in Context

Societycountry

EngineeringSystems Conceptual modeling

is not limited to any of the borders on the left.

It can be applied to systems in any domain and at any level of complexity.


System Engineering Phases

Accounts for~15% of the Development

Budget

Systems Engineering encompasses:• Requirements engineering• System architecture • Subsystem integration design• System testing design • Project oversight & management

SYSTEMENGINEERING

DETAILEDDESIGN

PRODUCTIONINTEGRATION TEST

Software Design

Mechanics Design

Electronics Design


Much of the system or product’s value, cost and risk are determined here.

Mistakes at this stage • affect all downstream phases,• are the most difficult and costly to correct,• determine project cost, timetable, overall success

TESTSYSTEMDESIGN

DETAILEDDESIGN

PRODUCTIONINTEGRATION

Why is Systems Engineering important?


Potential benefits of Systems Engineering

Better system quality and value Lower cost Shorter time-to-market

SYSTEMDESIGN

DETAILDESIGN

PRODUCTIONINTEGRATION TEST

Traditional Design

Time

Risk

SavedTime &

Cost“System Thinking” Design Time

Risk


Pre-Cost Commitment Investment vs. Total Cost Growth

% C

OST

GR

OW

THO

VER

TO

TAL

ESTI

MAT

E

Source Werner GruhlNASA Comptroller’s Office

Impact of “Front-End” Investment

2% 4% 6% 8% 10% 12%

IUE

140%

120%

100%

80%

60%

40%

20%

0%

-20%

COBE

ISEE

ERBE


% C

OST

GR

OW

THO

VER

TO

TAL

ESTI

MAT

E



2% 4% 6% 8% 10% 12%

IUE

140%

120%

100%

80%

60%

40%

20%

0%

-20%

COBE

ISEE

ERBE


% C

OST

GR

OW

THO

VER

TO

TAL

ESTI

MAT

E



2% 4% 6% 8% 10% 12%

IUE

140%

120%

100%

80%

60%

40%

20%

0%

-20%

COBE

ISEE

ERBE


% C

OST

GR

OW

THO

VER

TO

TAL

ESTI

MAT

E



2% 4% 6% 8% 10% 12%

IUE

140%

120%

100%

80%

60%

40%

20%

0%

-20%

COBE

ISEE

ERBE

% Investment inSystem Engineering Effort (SEE)

NASA Tracking 1980s

Total Program Overrun32 NASA Programs


NEED

Conceptual-Preliminary

Design

DetailedDesign and

Development

ConstructionAnd/or

Production

System Use,Phase out, and Disposal

%

25

50

75

100

Commitment to Technology,Configuration, Performance, Cost, etc.

Cost Incurred

System-Specific Knowledge

Ease of Change

Commitment, System-Specific Knowledge, and Cost

Systems Engineering is important early in a program to influence the design, when incurred costs are low and design changes are easy.

Time-Phased Sensitivity of SE to Total System Lifecycle Cost


Conceptual System Design Phase

PreliminarySystem Design

Phase

Detailed Design and Development

Phase

Desig

n In

fluen

ce

High

LowSystems Design and Development Progress

Individual Design Disciplines

Systems Engineering

Concept and Technology Development


Clicker Question

What statement is incorrect?1. Systems Engineering is multi- and interdisciplinary.

2. Early discovery of design errors saves expenses down the road.

3. Systems Engineering deals only with requirements definitions.

4. Focus on individual disciplines increases as we move from conceptual to detailed design.


Interim ConclusionsSystems Engineering effort improves development

qualityCost & schedule improvedHypothesis is supported by the data

Optimum Systems Engineering effort is 10-15%Matches data from NASA projectsCost & schedule overruns are minimized

Systems Engineering must have its ontology and modeling language!Like any engineering discipline, SE must be based on

solid foundations of a modeling language


Questions?


Benefit and Cost

Benefit is anything that increases the physical or mental well-being of a human or a group of humans.

Benefit usually come at some cost.

Cost is the sum of resources and efforts needed to extract or gain benefit.


Value

Value is benefit at a cost. Value = Benefit – Cost If the benefit is larger than the cost, then the value is

positive and the cost is worth spending (and vice versa).

Value is subjective – it is in the eyes of the beholder, who is the beneficiary.

Some processes provide value to some beneficiaries.

Such processes are called functions.


Function

A function is a process that delivers value to a beneficiary.

Function is also an attribute of an object, which describes: the rationale behind the existence of that object the intent for which it was built the purpose for which it exists the goal it serves, or the set of phenomena or behaviors it exhibits.


Examples of Functions

1. Function: Print a document.2. Function: Frame a picture.3. Function: Show the time of day.4. Function: Cross a river.5. Function: Carry at least 2000 tons of wheat

every week across a distance of 400 Km.6. Function: Protect a large civilian passenger

aircraft from a terrorist missile attack.


Phrasing a Function as a Process

Given a function, we convert it to a process phrasing by using the gerund form at the end of the process name.

Example: Function: Show the time of day. Process: Time of Day Showing

Continue the example with these functions 1. Function: Cross a river.2. Function: Carry at least 2000 tons of wheat every week

across a distance of 400 Km.3. Function: Protect a large civilian passenger aircraft from

a terrorist missile attack.


Exercise: Phrasing a Function as a Process

Given a function, convert it to a process phrasing by using the gerund form at the end of the process name.Function: Cross a river. Process: Function: Carry at least 2000 tons of wheat every

week across a distance of 400 Km. Process: Function: Protect a large civilian passenger aircraft

from a terrorist missile attack. Process:


Exercise

Phrase three functions and their corresponding processes Function: Process: Function: Process: Function: Protect a large civilian passenger

aircraft from a terrorist missile attack. Process:


System

Performing a function (and extracting value) requires the operation of some object.

That object is called system.

A system is a function-carrying object.The function is the main process the system performs.


Stakeholders: Beneficiary, User, OwnerBeneficiary is the agent (human or group

of humans) who benefits from the system’s operation

User, or operator, is the agent who uses and operates the system.

Owner is the agent who orders, acquires, and owns the system.

In small systems, the three are the same.In large systems, they may be different.


For which of the following systems the Beneficiary, User, and Owner are different?1. Scissors2. Car3. Lightweight rail4. National Missile Defense System

Clicker Question


Preliminary Stakeholders Model Agent: A human or group of humans who handle the process and

enable it but are not affected by it. Denoted by the “black lollipop”. The double arrow is the effect link – denotes that the process

changes the object’s state. Why is the model not quite correct?


Other Stakeholders

Supplier, Contractor, Subcontractors

Government, Legislator

The Public

Specific systems have specific stakeholders.Any more stakeholders? For what systems?


The Three Main System Aspects

Natural and artificial systems alike exhibit three major aspects: Function: why is the system built; what value is it

expected to create?Structure: what are the system’s parts; how are

they combined to provide the function?Behavior: how does the system operate; how

does it change over time?


The Concept Behind a System

Function pertains to the goal the system is designed for.

In order to function (and provide value) the system must operate based on some idea.

This idea often makes use of the laws of nature and logic in some clever way.

Concept is the idea or working principles underlying the functioning of the system.


Examples for System Concepts

Given a function, propose at least two concepts for the system to be architected.

1. Function: Show the time of day.2. Function: Cross a river from one bank to the

other.3. Function: Carry at least 2000 tons of wheat

every week across a distance of 400 Km.4. Function: Protect a large civilian passenger

aircraft from a terrorist missile attack.


System Architecture

System architecture is the overall system’s structure-behavior combination, which enables it to attain its function while embodying the architect's concept. In terms of architecture, concept is the system

architect’s strategy for a system’s architecture. Examples:

Time Keeping system River Crossing system


Product vs. Service Product is a system that is produced by an entity

with the intent of selling it to another entity for a profit. It is a system that has a commercial value to its

manufacturer.

Service is a function provided by an entity to another entity for a profit. It is a function that has a commercial value to its providerThe provided uses a system to provide the service.


Clicker Question

What statement is incorrect?1. System architecture combines structure and behavior

to provide function.

2. Every function has exactly one concept by which it can be achieved.

3. Product is to object what service it to process.

4. For simple systems or products, the owner, user and beneficiary are one and the same.


Questions?


Model: An Abstraction

A model is an abstraction of a system, aimed at understanding, communicating, explaining, or designing aspects of interest of that system.

Modeling approaches and methods: Natural Language Mathematics Graphics-based: sketch, map, drawing … Physical …


A Language for Systems Engineering

Systems engineering is the youngest engineering discipline

Like any field of engineering, systems engineering needs to have a language for accurately and unambiguously specifying the system of interest.

In this language, system engineers and other stakeholders should be able to express the design concepts of the system under development in a concise and easily communicable way.


Things, and links that connect them, are the elements of any system

Just two types of things:

Object, which can be possibly stateful – a

Stateful Object – Object with States

Process Each thing stands alone as a concept in its own right Things and states are called entities. A Link connects two entities. Links and things are elements

A Universal Ontology for

Systems Science & Engineering


Object

An object is a thing that exists or can exist physically or informatically. The object's existence can be physical or

informatical (or conceptual, or logical). It can be as simple as a block of ice or a record

in a file, or as complex as an organization, a human brain, or a galaxy.


Object NamingObject naming is simple—it is the noun. It can be a phrases with more than one word:

Apple Cake Automobile Crash – note that every word is capitalized

The object singularity OPM principle:A name of an object must be singular. Plural has to be converted to singular. Convert a plural object to singular by adding the word "Set"

Ingredients (e.g., of a Cake) becomes Ingredients Set. "Set" is an OPM reserved word used for loops and iterations

on the set members.


Object State

A state is a possible situation at which an object can be, or a value it can assume, for some positive amount of time. A state does not stand alone It has a meaning only within, and in the context of, an object. Examples:

States of the object Organization can be private or public States of the object Record can be locked or unlocked

State names are not capitalized Exercise: Model these examples


Transformation

Transformation is the creation (generation, construction) of

an object or consumption (elimination, destruction)

of an object or changing the state of an object.

Transformation takes a positive amount of time.


Process

A process is a thing that transforms an object.In other words:

A process is a pattern of object transformation. By definition, a process must be associated with

at least one object, the one which the process transforms.

For exampleFreezing is a process that creates an Ice Block Melting is a process that destroys an Ice Block

Exercise: Model these assertions.


Process Naming The gerund process naming modeA process name is a phrase whose last word should be the gerund form of a verb, a verb with the "ing" suffix. If there are several choices, such as in Construction vs. Constructing, the

latter is preferable. This naming convention has two advantages

clarifies the dynamic nature of the process as a thing that happens rather than a thing that exists.

The ing suffix enables automated detection of processes. An object name can precede the gerund.

In Engine Igniting, the process Igniting transforms the object Engine by changing its state from shut down to running.

Adding an object before the process qualifies the process. For example, Wall Painting, Roof Painting , and Car Painting are similar yet different

processes.


Gerund process naming mode versions

The verb version: the gerund form of the verb verb + ing, as in Making or Crossing.

The noun-verb version: noun + verb + ing, as in Cake Making or River Crossing.

The adjective-verb version: adjective + verb + ing, as in Quick Making or Assisted Crossing.

The adjective-noun-verb version: a concatenation of an adjective with a noun with the gerund adjective + verb + ing, as in Quick Cake Making or Assisted River Crossing.

In these examples, the adjective qualifies the process (the gerund, which is a noun).

However it can also qualify the object (the noun), as in Sweet Cake Making or Wide River Crossing.

Where do we place the adjective of the process if we want also an adjective for the object? Quick Sweet Cake Making


The Emergence of MBSE

Systematic specification, analysis, design and implementation of new systems and products are becoming ever more challenging and demanding

Contradicting requirements of shorter time-to-market, rising quality, and lower cost are on the rise.

These realizations have provided the basis for Model-

Based Systems Engineering (MBSE) as a foundational field of study within systems engineering.


MBSE MethodologyMBSE calls for the development of a comprehensive

methodology, capable of tackling the mounting challenges that the evolution of new systems and products poses.

An MBSE methodology is a collection of related processes, methods, and tools that support systems engineering.

Modeling is a foundational engineering activity in an MBSE methodology.

The evolving model resulting from this activity is a central infrastructural entity

The model supports systems development, evolution, and lifecycle in a “model-based” or “model-driven” context.


Model Based Systems Engineering Benefits

• Shared understanding of system requirements and design– Validation of requirements– Common basis for analysis and design– Identification of risks

• Basis for managing complex system development– Separation of concerns via multiple views of an integrated model– Support for traceability through hierarchical system models– Facilitation of impact analysis of requirements and design changes– Support for incremental development & evolutionary acquisition

• Improved design quality– Reduced errors and ambiguity early on– More complete and consistent representation


Conceptual Modeling

Central to the MBSE approach is the activity of conceptual modeling:the creation of a model or inter-related models or views in

some formal languageThe model specifies at various levels of detail, and from

various viewpoints, how a system is structured and how it behaves in order for it to deliver its intended function.

Let us examine an OPM model of a generic product lifecycle engineering system.


The System Diagram (SD) of

Product Lifecycle Engineering


Zooming into Product Lifecycle Engineering


The System Map: A Tree View


The System Map: All the OPDs in one View


Zooming into the Details of Design


Zooming into the Details of Manufacturing


Zooming into Initial Shaping within Making


Zooming into Software Module Developing within Making


Zooming into Assembly & Testing


Zooming into Commerce


Zooming into Use & Service


SD1.4 - End Of Life in-zoomed

Product is physical.

Zooming into End-of-Life


Main Advantages of Systems Engineering with OPM

Clear, intuitive, consistent graphical and textual communication language among all stakeholders.

A comprehensible model of the systemThe model evolves throughout the system lifecycle. System animation and simulation for design level

debugging. Preservation of actionable knowledge for effective

maintenance and future generations development via OPCAT’s built-in evolution mechanism.


Summary

Product and system lifecycle ontology is needed as a common language among the various stakeholders.

OPM offers a foundational, domain-independent ontology that is based on the notion of stateful objects and processes that transform them.

Using OPM, we have constructed a model-driven ontology for products and systems throughout their lives.

Date post:	23-Feb-2016
Category:	Documents
Upload:	hastin
View:	39 times
Download:	0 times

Lecture 1: Introduction

Documents