Transcript Model for Semantic Dictionary Draft

Draft #8 of Concepts Needed
for System Static Structure
David W. Oliver
Version October 9, 2002
Wakefield, R.I.
1
Concept Model for Systems Engineering
Semantic Dictionary and Accompanying Model
The concept model consists of two interlocking parts. The first part is the
semantic dictionary that defines each term. It is currently captured in an Excel
spread sheet. The definitions have been written to satisfy the ISO standard for
writing definitions that can be found on the BSCW web site. The definitions are
an ordered set. Definitions lower in the set use terms found higher in the set.
This helps prevent circular definition. Since the definitions are not arranged
alphabetically, they are numbered with a reference number to aid in locating them.
Definitions according to the ISO standard define kinds of things, composition
of things from other things, and associations among things. When one reads
ten or more text definitions the usual mind finds it difficult to remember the
many relationships implied. Hence a model accompanies the semantic dictionary.
The dictionary explains meanings in natural language. The model captures the
multitude of relationships in a graphic form so that the relationships can be
scanned. The model is written in UML 1.X, with indications of semantics
that are missing from the language.
2
(3)
Domain
of Interest
(2)
Category
(5)
categorizes
(7)
(6)
Stakeholder
System
View
C
(1)
Environment
has view
SE_Thing
exhibits
C
has
(8)
Stakeholder
Need
(4)
Interacts with
System
satisfied by
(11)
(9)
System
Requirement
represented by
allocated to
Property
Reference
Property
reference for
statement of
(10)
derived from
(12)
(13)
Physical
Property
(14)
Structure
Behavior
C
C
Top Level Concept Model, Figure 1.
allocated to
budgeted to
3
Top Level Model
The model needs to be read with reference to the definitions in the semantic
dictionary. It starts with SE_Thing that is any thing on which repeated
measurements can be made for the engineering purposes of interest. This is
a necessary definition because otherwise it is not possible to verify that a
design or implementation meets its requirements. SE_Thing is built from
SE_Thing in a hierarchy. The aggregation symbol has a small “C” in it to show
that what is meant is a decomposition into all of the parts. The special notation is
used because this concept is missing form UML 1.X.
The Domain of Interest constitutes all the things of interest to the application.
System is a kind of SE_Thing and thus it is built of systems in a hierarchy
and it must have measurable characteristics that are repeatable. What makes
the System unique is that it has well defined relationships with all of the things
with which it interacts. The collection of those things is its Environment. To
have a system it is necessary to characterize what is in the system and what is
in the environment along with the static and dynamic interactions between
system and environment. The Environment contains SE_Things and Systems.
4
Different persons in engineering, manufacturing, maintenance, and management
need different sets of information about the system. Manufacturing personnel
need to know about all the materials, nuts and rivets that go into the system and
how they assemble together. Maintenance personnel need to have diagnostic
information and deal with replaceable units of the system. There are a very large
number of such useful collections of information, each with its own context.
System View provides for the collection of such sets of information, each set in
a particular context.
An important subset of things in the environment are the Stakeholders. These are
all the persons and organizations with a need, preference, or interest in the system.
Stakeholders may include manufacturer, owner, user of owner’s services, user
of the system, operator, maintainer, government regulator. Stakeholder Need
represents their need, preference, interest, etc. in the system. If the System is
designed and implemented well, then it satisfies these needs in a manner that is
superior to competitive systems. It sells in the marketplace.
5
A Property is a named measurable or observable attribute, quality or
characteristic of an se_thing. If you can measure it or observe it it is called a
property. Properties have units, values, variances and probability distributions
associated with them. They may be looked up in handbooks of properties of
standard materials, they may be calculated from the structure of the thing, or
they may be measured directly. In general they are tensors and may be a function
of time. Because of the multiple ways of arriving at a property and its values, it
is important to have a Property Reference that establishes the source of the
information.
A Requirement is a statement of a Property that a System shall exhibit. The
relationship to System is handled by allocating the requirement to the system that
shall exhibit that property. This formality allows the engineer to consider
alternative allocations to different systems that may fulfill the requirement. It is
fundamental to trade-off among solutions. Requirements originate from
Stakeholder Needs. As the design proceeds in levels of detail, requirements
are derived from other requirements. These “derived from” relationships are
preserved as traceability relationships. In a real world problem requirements
will be changed from time to time. It is critical to trace from a requirement
that has changed to other requirements impacted by that change.
6
It is useful to distinguish among three kinds of properties.
• Structure, the description of how a system decomposes into its parts
and how the parts assemble to make the whole.
• Behavior, what the system does in response to the things in its
environment. This includes both desired responses that satisfy needs,
and prevention of undesired responses (failures) that can cause injury,
destruction, or loss.
• Physical Property includes all the measurable or observable attributes,
qualities or characteristic of an se_thing that cannot be observed
in interaction with the environment. Additional instruments or tools
are required to make the measurement or observation. Mass may
require a scale for weighing, index of refraction may require use of
an optical instrument.
These three kinds of properties are described separately and then
interrelated. This principle supports the consideration of alternatives.
7
(14)
Structure
C
(19)
(17)
Interface
Description
described by
(15)
System
Assembly
Port
1
C
C
1
Interconnection (18)
(16)
Link
System Static Structure, Figure 2.
8
Structure
Structure is built from System Assembly, Port, and Interface Description.
Structure decomposes hierarchically. This forces System Assembly and Port
to also decompose hierarchically.
System Assembly
The System Assembly is simply a part or component list. The name used
follows the STEP manufacturing point of view of looking at a part or
component and talking about it as an assembly because their job is to
assemble it. This is a place where it may be advisable for clarity to use the
words component or part as an alias for System Assembly.
Port
Each System Assembly (part or component) attaches to others at particular
locations. These locations are called Ports. This is a familiar idea when
one thinks of the port on a power cord that plugs into a port on the wall
to get electric power. It also applies to the surface of a bridge, a port, that
interacts with wind, a port. In the second case the concept is less intuitive
and more formal but it works. Ports connect to ports.
9
Interconnection
Interconnection specifies which ports attach to which other ports. Together
System Assembly, Port, and Interconnection specify how parts go together
to constitute the whole. This description does not include Behavior or Physical
Properties.
Interface Description
Each port has associated with it a description, an Interface Description, that
describes the geometry, forces, transferred material or energy or information,
protocols, how to assemble to it, and tests that may be required of the
port-to-port connection. For two ports to be interconnected their interfaces
must be compatible.
Structure, Behavior and Physical Property
Structure, Behavior and Physical Properties are described separately. Behavior
and Physical Properties are allocated or budgeted to System Assembly to
complete the description.
10
Behavior
Behavior is built from Function, I/O (Input/Output), and Function Ordering
as shown in Figure 3. Any SE_Thing may be I/O (Light blue shows an
entity comes from Figure 1.). A Function is a entity of transformation that
changes a set of inputs to a set of outputs. Function Ordering orders the
functions such that it is possible to represent sequence, concurrency,
branching, and iteration.
There are two major forms of representing Behavior. The continuous form
emerged in systems engineering in the 1970’s. It provides for completed
functions to enable succeeding functions, for I/O to trigger functions, and
for ordering operators to represent sequence, branching, and iteration. The
SEDRES model represents this with a Petrie net model. UML 2.0
contributors may be using a Petrie Net model. If so, then these two models
need careful comparison.
The discrete for of behavior representation emerged from automata theory
11
(1)
SE_Thing
Light blue background means this
entity comes from Figure 1.
C
(12)
Behavior
C
(21)
(20)
orders
Function
I/O
C
(22)
Function
Ordering
C
generates
and
consumes
1
(24)
External
Function
(6)
Environment
allocated to
(23)
Internal
Function
(4)
allocated to
System
2
generates and consumes
Behavior, Figure 3.
12
and has matured into State Charts that provide for state explosion in highly
concurrent models. SEDRES has a representation for this and has
demonstrated model transfer between Statemate and Teamwork Real Time
tools. In the UML community Action Semantics are to provide a basis for
state based behavior. These two approaches require careful correlation. The
concept model here does not go beyond the very general notion of function
ordering, but notes the critical importance of correlation among emerging
detailed models.
Structure and Physical Properties
Physical Property, its relationship to the Structure hierarchy and to analysis
is shown in Figure 4. The key concept is that performance, behavior and
physical properties of the whole results from the structure, the behavior and
physical properties of the parts. They are not related to a class tree.
13
Analytical_representation
(25)
assigned to Parameter_assignment
parameter_value
assigned_parameter
model_parameter_assignment (33)
model_representation
analytical_representation_name
Unit
(32)
measured in
assigned by
(13)
(31)
Physical
Property
Model_parameter
modeled by
represented by
type_name
unit of measure
reference_document
parameter_type
valid_range
default_value
(34)
Analytical_model
name
representation_language
reference_document
parameter
source_code
(26)
has
Name
ID
Property
Value
mean
variance
probability_
distribution
histogram
assigned to
(27)
(28)
Required/
Budgeted
Property
Value
(14)
(30)
(29)
Calculated
Property
Value
Target
budget
Property
Value
Measured
Property
Value
Structure
declared
to have
C
(19)
Interface
Description
working
target
measured
to have
(15)
(17)
described by
calculated
to have
System
Assembly
Port
1
C
C
1
Interconnection (18)
Structure and Physical Property, Figure 4.
14
Discussion of Figure 4.
System Assemblies in the system assembly tree all have Physical Properties such
as mass, power consumption, geometry, MTBF, drag coefficient, etc. The
Physical Properties are assigned to a particular System Assembly. A Physical
Property has a name and an ID that identifies it uniquely. For example, many
different System Assemblies have the Physical Property mass. Consequently
each of these assigned Physical Properties needs an ID. Each has an associated
unit in which it is measured.
A Physical Property assigned to a particular System Assembly has values. The
value may be expressed as a mean, a mean with variance, a probability
distribution, or a histogram. The value goes through a series of versions as the
system definition evolves. The System Assembly is declared to have a Required
or Budgeted Value.
The System Assembly may have a Target Budget Property Value used as a guide
or target as designers consider alternatives. A System Assembly, as a whole,
may have a Calculated Property Value based on analysis of the properties,
behaviors and interactions of its parts. When a System Assembly is built, it may
have a Measured Property Value.
15
Discussion of Figure 4.
Calculated Property Values - Analytical Modeling
Any one assembly is an interconnection of assemblies one tier down in the tree.
The emergent properties of any assembly are a result of the properties,
interconnection,and interaction of the sub-assemblies from which it is built. The
relationships may be very non-linear in the physical world as observed with
phenomena like combustion and friction.
.
The basic relationships for analytical modeling of emergent properties
and budgeting of properties are shown in Figure 4. A set of engineering
equations or estimates, analytical models, are used by systems engineers
to budget properties to the interacting sub-assemblies as a guide to
designers at the lower level. When designs for all of the sub-assemblies
are available, their individual properties and interactions are better defined.
The same equations are used to calculate the emergent properties of the
complete assembly. The fidelity of the calculations increases as the
work proceeds.
16
A System Assembly, as a whole, may have a Calculated Property Value based
on analysis of the properties, behaviors and interactions of its parts. This is
accomplished by estimation or by an analysis that solves the relevant
engineering equations. This makes it necessary to represent physical properties
as parameters in the equations of the relevant analysis model. Model Parameter
provides this parameterization. It has an attribute of its of the unit of measure
applicable to the analysis. This may be different from the unit assigned to
Physical Property. The reference_document attribute specifies the
standard document that contains the reference for the Model_parameter. A
default value and valid range can be specified when needed.
Parameter_assignment assigns parameters to the analytical equations that must
be solved, Analytical _representation. Each Analytical_representation may have
associated with it several Analytical_models that provide answers at different
levels of fidelity and with different efforts of computation.
17
Emergent Properties and Budgeting of Properties
Example
One may wish to develop a car that can accelerate from zero to sixty miles
per hour in 6.5 seconds or less. This is a required emergent property of the car.
This behavior is a result of the power of the drive train, the air resistance of the
body, the total mass of the car, and the friction of the tires on the road.
These parameters are inter-related by a second order differential equation.
The differential equation is first used to budget target values of mass, power,
drag coefficient, and tire friction to the appropriate components as targets
for the designers. When the designs are available with definite property
values, the same equations are used to calculate the emergent property,
time for acceleration from zero to sixty mph for the car.
Note that there may be several distinctly different approaches to the solution
of what sub-components to use. Thus it is useful for the assembly to have
relationships that indicate if it is an alternative or is selected as a solution, if it
meets requirements, and what its regularization function value may be as the
basis of selecting a particular solution from among the alternatives.
18
Car
Weight, Wc
Time to Accelerate
0 to 60 mph, Ta
C
Body
Weight, Wb
Drag Coefficient, Dg
Chassis
Weight, Wch
Drive Train
Weight, Wdt
Power, Pdt
Tires
Weight, Wb
Friction, Tf
Electrical
Weight, We
Engineering Equations
Wc = Wb + Wch + Wdt + Wh + We
Wc * d2x/dt2 + Dg * dx/dt = Tf *Wc
0 < dx/dt < Pdt/(Tf*Wc)
Wc * d2x/dt2 + Dg * dx/dt = Pdt/(dx/dt)
Pdt/(Tf*Wc) <dx/dt
initial condition: x=o, dx/dt=0
compute: t, Ta, when dx/dt=60 mph
Figure 5.
Ta is an emergent property of Car. Dg is an assembly property of Body
19
Example of Figure 5.
The Table below is a crude map of the equations in Figure 5. Into the concept
model defined in Figure 4 for the car example. Only the properties of car have
been mapped. Note there are two analytical models. One is very simple and
assumes constant traction once the car is in motion and rolling friction applies.
The second is of higher fidelity and uses traction vs. Rpm. from actual engine
data, including transmission gear changing.
System
Assembly
Car
Car
Physical
Property
Weight
Unit
Pounds
Time to
accelerate
0 - 60 mph Seconds
Required
Model
Unit of
Value Parameter measure
Default
value
3500 + 100
Wc
Kilograms
3500 + 100
> 6.5
Ta
Seconds
6.5
Parameter
assignment
Analytical
repr.
Analytical Representation
model
Language
Independent
Conservation
variable
Conservation of of mass; see
equation 1
mass
equation
Version 1:
Force equation Constant
time variable
with drag
traction; see
equation 2,3
coefficient
equation
Version 2:
traction vs.
RPM; see
equation
Math-ML
Math-ML
Math-ML
It is hoped that reviewers Frisch and Thurman will correct Figures 4. and 5.
and this table.
20
Some definitions taken from the report of Frisch and Thurman are captured
on the next three slides.
Model_parameter
A Model_parameter is a formally declared variable of the analytical model provided for an external application to
populate at execution time in a computing environment.
EXAMPLE: In Spice, temperature is a Model_parameter that may be set at the execution time.
The data associated with this application object are the following:
default_value
parameter_type
reference_document
type_name
unit_of_measure
valid_range
default_value
The default_value specifies a value for the parameter. The default_value need not be specified for a particular
Model_parameter.
parameter_type
The parameter_type specifies either a boolean_property_type, a logical_property_type, a physical_property_type, or a
string_property_type for the Model_parameter.
21
reference_document
The reference_document specifies either a specific document or an identifier for the standard document that contains the
reference for the Model_parameter.
type_name
The type_name specifies the string used as the human-interpretable type name for the Model_parameter.
unit_of_measure
The unit_of_measure specifies the string used as the descriptive label for the unit of measure associated with the
Model_parameter. The unit_of_measure need not be specified for a particular Model_parameter. The representation of
units described in ISO 10303-41 shall be used. Note that the unit used in requirements specification may differ from
the unit_of_measure used in analysis
valid_range
The valid_range specifies the appropriate range of values of the Model_parameter. The valid_range need not be specified
or a particular Model_parameter. There may be more than one Coordinated_characteristic for a Model_parameter.
The valid_ranges need not be contiguous.
NOTE: The prefixes of the valid_range and default_value may be different as long as the base units are the same type.
Formal constraints:
UR1: The combination of the reference_document and the type_name shall be unique within a population of
Model_parameter.
22
Parameter_assignment
Parameter_assignment provides actual values for characteristics declared formally by the Model_parameter.
The data associated with this application object are the following:
assigned_parameter
parameter_value
assigned_parameter
The assigned_parameter declares the formal parameters assigned values by the
Parameter_assignment.
parameter_value
The parameter_value specifies actual values for the Parameter_assignment.
Formal constraints:
WR1: The type of units of the parameter_value shall be the same as that of the assigned_parameter.
23
Analytical_representation
An Analytical_representation is the association of specific properties of specific System Assemblies with an Analytical_model in
order to unambiguously characterize the performance of a specific System Assembly.
NOTES:
1.This entity accomplishes a function similar to the parameter assignment part of a statement in a Spice netlist, or a function or
subroutine call in a computer program. This capability is useful where the parts in the library have many parameters, not all of
which apply to each simulation model that could be used for the part. This entity matches up the correct parameter values with
the correct model.
2.The properties specified should be in accordance with the capabilities and limitations of the Analytical_model. That is, the
mathematical formulations in the Analytical_model apply over limited ranges of real product characteristics and environmental
characteristics.
3.This part of ISO 10303 does not standardize qualification of Analytical_representations for an intended usage.
The data associated with this application object are the following:
analytical_representation_name
model_parameter_assignment
model_representation
analytical_representation_name
The analytical_representation_name specifies the string for the human-interpretable identifier for this Analytical_representation.
model_parameter_assignment
The model_parameter_assignment specifies the role of the Parameter_assignment for the Analytical_representation. There shall
be one or more Parameter_assignment for the Analytical_representation.
NOTE: For each parameter declared in a model definition, an actual value must be assigned when that model is referenced,
unless there is a default assignment included in the source code for the model.
24
model_representation
The model_representation specifies the Analytical_model as the basis model for the Analytical_representation.
Formal constraints:
UR1: The analytical_representation_name shall be unique within a population of Analytical_representation.
WR1: Each member of model_parameter_assignment.assigned_parameter shall be a member of model_representation
model_parameters.
NOTE: Only parameters declared in the model_representation are assigned values.
Analytical_model
Provides a mathematical description of the properties of a system. An Analytical_model may be a Library_model.
NOTES:
1.In this part of ISO 10303 an Analytical_model includes the variable declarations of the mathematical description but may not
include the assignment of actual values for the variables declared.
2.This part of ISO 10303 provides support for computer systems to verify type consistency between product data defined in
this part of ISO 10303 and product data captured by Analytical_models.
3.This part of ISO 10303 describes the interfaces (ports) to an Analytical_model and provides support for type checking of the
units used for the parameters that may be assigned values for an Analytical_model.
25
Analytical_model
An Analytical_model provides a mathematical description of the properties of a system. An Analytical_model may be a
library model.
NOTES:
In this part of ISO 10303 an Analytical_model includes the variable declarations of the mathematical description but may
not include the assignment of actual values for the variables declared.
This part of ISO 10303 provides support for computer systems to verify type consistency between product data defined in
this part of ISO 10303 and product data captured by Analytical_models.
This part of ISO 10303 describes the interfaces (ports) to an Analytical_model and provides support for type checking
of the units used for the parameters that may be assigned values for an Analytical_model.
EXAMPLE: consider the case where actual values are not included: the Analytical_model for a resistor that is coded in
pseudocode. When the Analytical_model is referenced by an analytical_representation, literals will be supplied for items
declared in the interface; both connections and their parameters, and the simulator will ensure that types are compatible.
NOTES:
Usually the system is exercised in experiments to evaluate the usefulness of the system in the intended application.
The language, syntax, and internal semantics of an Analytical_model are not specified by this part of ISO 10303.
This part of ISO 10303 provides complete support for exchange of units, including SI units, derived units, and user
declared units.
26
This part of ISO 10303 provides complete support for prefixes of units.
The data associated with this application object are the following:
access_mechanism
name
parameter
reference_document
representation_language
source_code
access_mechanism
The access_mechanism is an inverse relationship that specifies that the existence of the Analytical_model is dependent
on the existence of the Analytical_model_port that specifies the Analytical_model as its accessed_analytical_model.
There shall be one or more Analytical_model_port for an Analytical_model.
name
The name specifies the string that is the identifier for the Analytical_model.
parameter
The parameter specifies the role of the Model_parameter for the Analytical_model. There shall be one or more
Model_parameter for a particular Analytical_model. Figure am illustrates the use of parameters.
NOTE: Parameters of a model are separated from their connections to support the nodal formulation.
27
reference_document
The reference_document specifies the role of the document for the Analytical_model. The reference_document
includes interface specifications for Analytical_models of interest to the enterprise.
representation_language
The representation_language specifies the Language_reference_manual that defines the semantics and syntax of the
computer interpretable strings in which the Analytical_model will be encoded. Figure am illustrates how the
representation_language is specified and coded.
NOTE: Only representation_languages that use characters from the ASCII code are supported by this part of ISO 10303.
source_code
The source_code specifies the role of ths specification for an Analytical_model. The source_code contains the
source code for the Analytical_model. Figure am illustrates how a source_code is specified and coded.
Formal constraints:
UR1: The combination of the name and the reference_document shall be unique within a population of Analytical_model.
UR2: The combination of the name and the source_code shall be unique within a population of Analytical_model.
28
Allocation of Requirements
Depending upon their content, requirements are allocated to different
parts of the information model. Requirements describing functions are
allocated to functions, etc. This is a useful way of classifying requirements
for the purpose of creating a logically consistent model or description of a
system.
Within systems engineering there is no single standardized way of classifying
requirements and many different classifications for different purposes are
in use. The classification given in Figure 6. Is defined as shown because it
is useful for the purpose allocating or assigning requirements.
It is not possible to enforce any process with an information model and AP233
is intended to support both pest practices and other practices in use. Hence, any
collection of requirements may contain compound requirements, contradictory
requirements, and non-feasible requirements. Consequently the
generalization/specialization of Figure 6. Is non-exhaustive and inclusive.
29
A Requirement Classification,
needed to show how requirements are
allocated to Behavior & System Structure
(10)
System Requirement
non-exhaustive
inclusive
Effectiveness
Measure
(42)
Functional
Requirement
based on content and allocation
Temporal
Requirement
(35)
(36)
User Defined
Physical
Property
Requirement
Interface
Requirement
(38)
(37)
Imposed Design
Requirement
(39)
Reference
Requirement
(40)
Classification of Requirements for the Purpose of Allocation, Figure 6.
30
Property
Requirement Allocations, Figure 7.
C
Behavior
System Static Structure
C
Physical
Property
C
C
assigned to
assigned to
C
Function
Function
Ordering
order
Port
Interface
System Assembly
allocated to
bound to
Reference
Source
assigned to
assigned to
Functional
Requirement
Temporal
Requirement
assigned to
(28)
assigned to
Interface
Requirement
Physical
Property
Requirement
points to
Reference
Requirement
based on allocation
non-exhaustive
inclusive
Requirement_S
Effectiveness
Measures
has
used in
has
Optimization
Direction
(43)
assigned to
I/O
consume
generate
Weight
(44)
Imposed Design
Regularization Function
used in
(45)
optimizes
31
Summary of Allocation Relationships
• Functional Requirements are assigned to to functions
• Temporal Requirements are assigned to functions
• Function is allocated to System Assembly (red used because of line crossings)
• I/O is bound to ports (red used because of line crossings)
• Interface Requirements are assigned to Interfaces
• Physical Property Requirements are assigned to System Assembly
• Imposed Design is assigned to the System Assembly on which it is imposed
• Reference Requirements point to a Reference Source that may contain
requirements of all the kinds in the classification
32
Physical Property and Time
Figure 8. Shows draft models for Physical Property and Time. Physical Property
and System Assembly are under study by a team member and improved models
are expected for Figure 8. and Figure 4.
The model for time in Figure 8. is preliminary and needs discussion.
• Continuous Time is a dimension along with three spatial dimensions used by science
and engineering to describe reality using math. It has no past, present or future.
• Present Time recognizes a standard of year, month, week, day, hour, minute, and
second to represent past, present, and future. It is the basis of plans and schedules.
• Time Interval provides a time duration that may be assigned to a task or function to
represent how long the task will take for completion.
• Start Time is a Present Time that states where in Present Time a Time Interval
begins.
• Stop Time is a Present Time that states where in Present Time a Time Interval
ends.
33
Physical Property and Time
• Discrete Time is time represented by clock pulses of negligible duration.
In this approximation events occur on each clock pulse.
Time is one of the most accurately measured quantities that we have. Current
accuracy of measurement is about one part in 10 -13. Research underway may
extend this to 10 -17. Many properties now have primary standards based in
part on time.
34
Refined Decomposition for Physical Property and Time, Figure 8.
Measurement
Infrastructure
uses
Measurement
Method
Time
Unit
Mean Value
Variance
Probability Distribution
measures
Physical Property
Name
Unit
Mean Value
Variance
Probability Distribution
Value Range
(13)
Continuous
Time
Present
Time
Start
Time
Time
Interval
Discrete
Time
Stop
Time
35
Systems Engineering Management
Three Models follow that are important to systems Engineering Management.
The models for verification and validation are at first draft level and need
discussion.
The model for Risk was discussed with the Risk Working Group at
the INCOSE 2002 symposium. AP233 is waiting for there corrections
and changes. The existing model is based on information from the
risk working group, NASA Goddard Risk Attributes in SLATE
‘GPM’ Data Base March 7,2002 (Dave Everett), and from NASA
JPL Risk Process Diagram
36
(10)
System
Requirement
Category
traces to
categorized by
categorized by
Verification
(46)
Requirement
(47)
Verification
Event
satisfied by
causes
causes
Risk
has
Verification
Requirement
(54)
Status
scheduled by
uses
Verification
Configuration
(53)
(52)
causes
performed with
(48)
Verification
Procedure
Issue
specified by
specified by
(50)
Verification
Plan
(49)
causes
assigned to
(51)
Organization
generates
37
(10)
System
Requirement
(8)
Stakeholder
Need
represented by
(7)
Stakeholder
has
involves
derived from
Category
traces to
categorized by
categorized by
(55)
Validation
Requirement
satisfied by
causes
(60)
(56)
Validation
Event
performed with
(57)
Validation
Procedure
causes
has
Risk
uses
Validation
Requirement
Status
schedules
Validation (58)
Infrastructure
specifies
causes
Issue
specifies
(59)
Validation
Plan
causes
assigned to
Organization
generates
38
Individual Risk
Risk Title
Risk ID
Context
Risk Owner
Originator
Date found
Date updated
combine to
Risk
Window_open
Window_closed
Risk_Handling
Time Frame
Priority
has
Status
Status Title
Status ID
Risk ID
Risk Title
Status Names:
Submitted
Retired
Approved
Related Risk
R-R Title
R-R ID
Risk Title
Risk ID
Select Rule
Category Name
drive
drive
implies
Likelihood
Risk Title
Risk ID
Type: a (%),b,c
Probability Distribution:
Name
Mean
Variance
Contingency Plan
Plan ID
Triggers
Date Applied
Date Closed
Closed by
Closing_Rationale
Mitigation_Effects
_Description
AP233 Draft Concept
Model for Risk
March 20, 2002
Lessons Learned
Lesson Title
Lesson ID
Lesson Date
Lesson Description
Lesson Category
incorporate
implements
Inputs
Technology
Program Plan
Schedule/Cost Constraints
Risk Management Plan
likelihood of
Consequence
Risk Title
Risk ID
Type: a,b,c
Consequence
number
Probability_
Distribution
Approach Strategy
Strategy ID
Description/Assumptions
Approach:
None assigned
Accept
Watch
Mitigate
Prevent
Transfer
resolves
has
n
Impact
Risk Title
Risk ID
Affected_Thing_Title
Affected_Thing_ID
Severity
39
Category
The decomposition tree for System Assembly is more than a simple parts
tree. At any node one may introduce a category of parts. For example, an
automobile may have several different engines that can be used in the
automobile, each providing a different level of economy and performance.
Categories are a grouping of elements into a set based on defined properties
that serve as selection criteria for which elements of all those in the universe
belong in that set Explanation: It is categorization that enables us to define
alternatives and create taxonomies for libraries. This is one of the forms of
generalization/specialization. Note that this is NOT INHERITANCE as found in
object-oriented software languages. Physical elements, matter and energy, do
not inherit their properties. Rather they posses the properties of themselves and
can be identified by measurement of those properties. For a discussion of these
issues in computer science see the work of Barbara Liskov and her CLU
language.
Note: the subcategories may be exclusive or inclusive and
the subcategories may exhaust the super category or not
there are four such possibilities
Category is the basic concept in the physical world to support specialization generalization.
40