Leveraging Alf for SysML, Part 2: More Effective Trade Study Modeling

Leveraging Alf for SysML
Part 2: More Effective Trade Study Modeling
Copyright © 2019 Ed Seidewitz / Model Driven Solutions, Inc.
Ed Seidewitz
Model Driven Solutions, Inc. ● http://www.modeldriven.com
ed-s@modeldriven.com ● @Seidewitz
http://slideshare.net/seidewitz

Goals
Part 1 –Simulation Modeling (Sunday)
• Learn the basics of the Alf action language for executable modeling.
• Learn how to use Alf as an action language in SysML models.
• Practice executing simulations of models that use Alf.
Part 2 – Trade Study Modeling (Today)
• Learn how to use the Trade Study Pattern.
• Use Alf together with parametric constraints in SysML models.
• Use simulation models in trade studies.

Prerequisites
• Participant
– Knowledge of SysML modeling using MagicDraw or Cameo System Modeler
– Some experience with model execution using Cameo Simulation Toolkit
– Introductory understanding of using Alf with SysML (e.g., from Part 1 of this tutorial)
• System (for hands-on exercises)
– Cameo System Modeler 19.0 SP2 (or MagicDraw and SysML)
– Cameo Simulation Toolkit 19.0 SP2 (included in CSM Enterprise Edition)
– Alf Plugin 19.0 SP2
• Slides: Available at https://www.slideshare.net/seidewitz

4
Installing the Alf Plugin
Plugin documentation is available at:
https://docs.nomagic.com/display/ALFP190SP2/Alf+plugin
Under Plugins
(commercial),
download / install the
Alf plugin v19.0 SP2.
Select Help ► Resource/Plugin
Manager to open the Resource/
Plugin Manager window.

Parametrics

Parametric Constraints
A constraint block is a generic
form of parametrized
constraint that can be used in
multiple contexts.
A constraint property is
a property whose type
is a constraint block.
Constraints are defined
using mathematical
equations.
Constraints are defined in terms of
parameters that can be bound to the
physical properties modeled for systems.
⚠️ Do not specify constraints
using Alf expressions.

Parametric Diagrams
A constraint property is a
usage of a constraint block.
A binding connector asserts
that the values of the connected
properties must be equal.

Airplane Mass Roll Up: Definition
The top-level assembly and each
part are all kinds of components.
The specific compositions
subset the general composition.

Airplane Mass Rollup: Execution
Executing this instance with
the given composition.
By default, solving is
done on initialization.
As a result, the total
mass is computed.

Hands On
Airplane Mass Roll Up

Create a Mass Roll Up project

Load the Alf Library and open the Alf Editor window

Create a Component block and totalMass operation
The total mass is computed
using an operation
This is a conditional expression, which
choses one of two operand expressions
to evaluate based on a condition.
This is equivalent to
this.sub->collect s (s.totalMass())
that is, it collects all the total masses of all
the subcomponents.
This reduces a sequence using the
given function (in this case, it sums).
Right click on the operation and
select Create Method ►
Behavior to open the Behavior
selection window.

Create the Airplane mass roll up definition
Drag the subsetted property onto
the subsetting property in order to
create a subsets relationship.

Create a Simulation driver block
Create an activity under
the Simulation block.
Enter Alf code to test the
roll up operation.

Create an Simulation instance model
Create composition links
between the instances.
Select the specific association,
not the general one.
Set all the component
masses.
Execute the Simulation
instance

Trade Studies

Trade study pattern
The trade study pattern
is a modelling pattern for
choosing the best of a
set of alternatives.
A parametric constraint
is used to test the “value”
of each alternative and
select the best one.

Trade study driver activity
The current alternative is responsible for
setting the current value, which triggers
the compare constraint.
 To be safe, there should be
a control flow to make sure
the expansion region does
not execute prematurely.

Area trade study
The alternatives for this trade study
are Rectangles of different areas.
The Area trade study specializes
the general Trade Study Pattern
and redefines the current
alternative to be a Rectangle.
A parametric constraint is
used to compute the
currentValue as the area
of the current alternative.

Area trade study configuration
The alternatives to be
configured are configured
using instance specifications.

Area trade study results
The “winner” is alternative
r3 with the highest area.

Hands On
Trade Study Pattern

Open the sample TradeStudyPattern project
…
Click on the Samples
button.
Select TradeStudyPattern
under Simulation.
 Be sure to save the project locally
before modifying it!
 After saving a local copy, load the
Alf Library and open the Alf Editor
window.

Set the animation speed
Open the Specification for each
SimulationConfig and set the
Animation Speed to 100.

Delete the old method bodies
Delete the old methods
for computeWithBest and
evaluateAlternative.

Create the evaluateAlternative method
Add an alternative parameter
to the evaluateAlternative
operation.
Right click on the operation and
select Create Method ►
Behavior to open the Behavior
selection window.
Choose either
Activity or
Opaque Behavior.
Enter the Alf code in
the Alf Editor window.

Create the evaluateAlternative method
Also create a method for the
compareWithBest operation,
and add Alf code.

Replace the doTradeStudy activity
Delete the content of the
doTradeStudy activity…
…and replace it with Alf code.

Run the simulations
Run the simulations, to
see if they still work.

Revise the compareWithBest operation
Add a value operation to
the Alternative block.
Delete the compare
constraint property. Update the Alf code for the
compareWithBest operation.
 Be sure to delete using ctrl-D,
not the delete key.

Add area operation to Rectangle block
Add an area operation,
and open its specification.
Choose Properties: All.
Search for the “redefined
operation” property.
Click here to select a
redefined operation.
Select value as the
redefined operation.
Search for the “value”
operation.

Create the area method
Correct the spelling
of “hight” to “height”.
Delete the rArea constraint
property.
Create a method for the
area operation.
ⓘ To show the “redefines”
annotation, open the Rectangle
Symbol Properties and set Show
Operation Properties to true.

Add hp operation to Engine block
Delete this connector.
Add an hp operation, redefining
the value operation.
Create a method for the hp
operation

Redefine hp operation for HybridEngine block
Add an hp operation,
redefining the Engine::hp
operation.
Delete the Sum constraint
property.
 The component hp properties
need to be made public!
Create a method for the hp
operation.
A super invocation calls the
original operation method from
the ”superclass” block.

Hands On
Heating Simulation
Trade Study

Share packages from the Trade Study Pattern project
Share the three packages
from the (modified)
TradeStudyPattern project.

Use the TradeStudyPattern project in Heating Simulation
Open the Heating Simulation project and
select File ▶︎ Use Project ▶︎ Local Project to
attach the TradeStudyPattern..
Create a Trade Study package.

Add a block definition diagram for Trade Study
Create a Heating Simulation Trade
Study block as a specialization of
the Trade Study Pattern.
Redefine the alternatives
reference property.
Add a generalization from
Heating Simulation to Alternative.
Redefine the value
operation from Alternative.

Add signals to provide an asynchronous protocol

Create the Heating Simulation Trade Study state machine

Create Start and Stop signals and receptions
Make this association
end navigable.
Make this association
end navigable.

Update the Environment state machine

Update the heat operation on the Climate block

Update the Climate state machine

Update the Heater state machine

Create a Heating Simulation state machine
Also add a referential
attribute to Heating
Simulation Trade Study.

Create a simulation configuration
Note different values for
temperature attributes.
Set the animation
speed to 100.
Set the evaluation
target to the study.
 The SimulationConfig needs
to be created on a Simulation
Configuration Diagram.

Run the simulation

Leveraging Alf for SysML, Part 2: More Effective Trade Study Modeling

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