July 2, 2022 1 An Overview of the Systems Modeling (SysML) Specification Shana L. Lloyd Julie A. Street The Aerospace Corporation Systems Modeling Language (SysML) and Unified Model Language (UML) are a registered trademarks of Object Management Group, Inc. in the United States and/or other countries
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7 February 2014 1 An Overview of the Systems Modeling (SysML) Specification Shana L. Lloyd Julie A. Street The Aerospace Corporation Systems Modeling Language.
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April 10, 2023 1
An Overview of the Systems Modeling (SysML) Specification
Shana L. Lloyd
Julie A. Street
The Aerospace Corporation
Systems Modeling Language (SysML) and Unified Model Language (UML) are a registered
trademarks of Object Management Group, Inc. in theUnited States and/or other countries
April 10, 2023 2
Outline
• Background
• Request for Proposal (RFP)
• The Spec
• More Information
April 10, 2023 3
Background
April 10, 2023 4
Background
• The SE community is moving from a document-centric approach to a model-driven approach– Need integration of SE models with
other discipline-specific models (software, hardware, simulation & analysis, etc.)
• Unified Modeling Language (UML) was designed for Software Engineers– Lacks all of the mechanisms
needed for Systems Engineers
April 10, 2023 5
SysML
“SysML is a general-purpose graphical modeling language for specifying, analyzing, designing and verifying complex systems that may include hardware, software, information, personnel, procedures, and facilities.”
April 10, 2023 6
What is UML?
• Unified Modeling Language (UML)– Object modeling and specification language used in
software engineering– Object Management Group (OMG) manages and
maintains UML
• Goals of UML– Provide a method of consistent and effective
communication among software engineers– Provide a way to understand software designs
without code or psuedocode– Specify, visualize, and document software designs– Raise the level of abstraction to focus on system
aspects rather than implementation details– Provide multiple views of the system
April 10, 2023 7
Modeling in UML
• What can you model in UML?– Structures
• Captures the physical & compositional structure of the system
• E.g. Class Diagrams & Deployment Diagrams
– Behaviors• Captures the high level behavior of the system• E.g. Use Cases & Activity Diagrams
– Interactions• Captures the details behind the behavior of the
system• E.g. Sequence Diagrams, Collaboration Diagrams
and Timing Diagrams
comm on use ca se
use case 1
<<include>>
Actor1
Actor2use case 2
<<include>>
System
comm on use ca se
use case 1
<<include>>
Actor1
Actor2use case 2
<<include>>
System
April 10, 2023 8
Object Management Group (OMG)
• OMG is leading the SysML Effort• Who is OMG?
– International software consortium established in 1989– Members include vendors, developers, and end users
• Mission – “To help computer users solve enterprise integration
problems by supplying open, vendor-neutral portability, interoperability and reusability specifications based on Model Driven Architecture (MDA).”
• Established Standards– Common Object Request Broker Architecture (CORBA) – Unified Modeling Language (UML)– Meta-Object Facility (MOF) – And more
April 10, 2023 9
• Purpose of Model Driven Architecture– Separate the specification of system functionality
from specification of implementation (i.e. a specific technology platform)
• Concepts of MDA1. Model : presentation of a function, structure,
and/or behavior of a system
Model Driven Architecture (MDA)
2. Platform: a subsystem that provides functionality through interfaces and usage patterns that any system can use without knowing the details of how that functionality is implemented
3. Platform Independent Model (PIM): A system model that contains no platform-specific information
4. Platform Specific Model (PSM): A system model that includes technology and platform-specific information
5. Mapping: Transforming the elements of one model to another model
April 10, 2023 10
The Request for Proposal
April 10, 2023 11
SysML Specification Timeline
2003
Initial spec (v0.3) presented to INCOSE
International Workshop
Jan
Initial submission to OMG
Feb
Spec v0.9 submitted to OMG
MayJan
Sterotypes & Model Libraries
Chapter submitted as an amendment to
spec v0.9
Multi-vendor demonstration of v0.9
spec presented to INCOSE.
July Aug Nov AprilDec
Draft specs submitted
INCOSE & OMG
evaluate submissions
SysML 1.0 Spec Submitted to OMG
Mar
UML for SE RFP issued
May
2004
2005 2006 July
OMG announces
the adoption of OMG SysML
April 10, 2023 12
Request for Proposal (RFP) Background
• Decision to pursue UML for systems engineering made at INCOSE International Workshop in January 2001
• Memorandum of Understanding between OMG & INCOSE signed
• Systems Engineering Domains Special Interest Group (SE DSIG) chartered
• SE DSIG Kickoff Meeting Sept. 2001
SE DSIG Activities– Issued of Request for
Information (RFI)
– Developed Systems Engineering Conceptual Model
– Collaborated with UML 2.0 submission teams
– Developed a requirements analysis
April 10, 2023 13
SE Conceptual ModelCaptures essential
concepts of systems
engineering in form of a UML model
Used as input for SysML
requirements
April 10, 2023 14
Request for Information (RFI)
• RFI Issued February 2002
• Reponses Due August 2002
• Goals of the RFI– Help formulate SysML
requirements– Identify potential
solutions– Identify interested
stakeholders
Companies that Responded• Tofs AB
• BAE Systems, CNI Division
• Rational Software
• Volvo Car Corporation
• Lockheed Martin
• Frank Matyskiela Systems Engineering Consul
• I-Logix
• INCOSE OOSEM WG
• MITRE
• Georgia Tech
• ARTISAN Software Tools
• Holistic Systems Engineering
• Project Technology
April 10, 2023 15
• Solicited submissions that specify a customization of UML for Systems Engineering (SysML)– Released March 28,2003
• Specification Goals– Support modeling a broad range of
systems• Hardware, software, data, personnel,
procedures, and facilities
– Capture system information precisely and efficiently
– Allow for the analysis and evaluation of the modeled system
– Provide clear communication of systems information among stakeholders
SysML Request for Proposal (RFP)
April 10, 2023 16
Proposal Requirements• Express models in OMG modeling languages (i.e. UML)• Be precise and functionally complete• Identify mappings between platform independent model
(PIM) & platform specific models (PSMs) • Specify what features are required in implementations
and which are optional• Be compatible and useable with existing OMG specs• Justify changes or extensions to existing OMG specs• Preserve maximum implementation flexibility• Allow for independent implementations that are
substitutable and interoperable• Be compatible with ISO’s Reference Model of Open
Distributed Processing [RM-ODP]• Address security questions and concerns• Specify the degree of internationalization support
April 10, 2023 17
Spec Mandatory Requirements
• Structure– System hierarchy– Environment– System interconnection
• Uses UML 2.0 profile mechanisms to specify extensions for SysML
UML not required by SysML
SysML extensions to UML
(Have no counterpart in UML or place UML constructs)
April 10, 2023 24
Reuse & Extensions
UML reused for SysML• Actions• Activities• Classes• General Behavior• Information Flows• Interactions• Models• Profiles• State Machines• Structures• Use Cases
Extensions to UML• SysML::Model Elements refactors
and extends Kernel • SysML:: Blocks reuses Composite
structures & Model Elements• SysML::ConstraintBlocks extends
Blocks• SysML::Ports & Flows extends UML
Ports• SysML::Activities extends UML
Activities• SysML::Allocations extends UML
dependencies• SysML::Requirements extends
Classes and dependencies
April 10, 2023 25
SysML Diagram Taxonomy
SysML Merge Team Submission v0.99 p.9
April 10, 2023 26
Four Pillars of SysML
April 10, 2023 27
SysML Summary
View Major Extensions Benefits
Structural Model Elements Standard way to capture views and design decisions
Blocks Flexibility to model non-softwarecomponents with custom properties
Ports and Flows Differentiate between what could and what actually does travel through a port
Constraint Blocks Ability to integrate analysis in designs
Behavioral New Activity Diagram More control over activities, ability to model continuous streams and path probability
Stereotypes New stereotypes for easily behavior classification
Crosscutting Allocations More flexible mapping capabilities
Requirements Ability to model requirements, their relationships, and links back to the design diagrams
• Use Constraint Blocks– Internal Block Diagrams– Parametric Diagrams
• Specialized internal block diagram• Must be bound to Constraint
Parameter
SysMLSysML•Constraint Block•Constraint Property
UML4SysMLUML4SysML•N/A
April 10, 2023 37
Structural – Constraint Blocks
Block Definition Diagram
Defines the constraint blocks
Parametric DiagramShow how the constraint
blocks are used
Integrate analysis in
design
Modified version of figure 10-2 & 10-3 in Submission Team spec v 0.98
Property constraints
Nested property constraints
April 10, 2023 38
Structural Overall Assessment• Advantages
– Easy to Understand with UML 2.0 Knowledge• A lot of UML 2.0 reuse • Clear equivalent UML 2.0 diagrams & notations
– Capturing System Elements Easy• Blocks flexible enough to model any element• Custom compartments powerful for capturing element specialized characteristics
– Capturing Design Decisions in Design Easy• Rationale stereotype capturing design decisions any diagrams• Will need to define standard for its usage.
• Limitations– Consistency Difficult
• Many different views & viewpoints can make consistency difficult
– System Element Uniformity• Different groups will use different compartments to model same element• Potential to lead to domain specific extensions
April 10, 2023 39
Behavioral -Activities
• Activities– Typically used for business
process modeling or logic in a single use case
– Extends UML 2.0 to support disabling of actions that are already executing
• Diagrams– Activity Diagram
• Some modifications for UML 2.0 diagrams SysMLSysML
• Overwrite: Stereotype added to a object node to signify that if a new token arrives, it will replace any existing tokens
• Optional: Stereotype added to a parameter to signify it is not required for activity to begin execution
• Probability: Stereotype added to signify probability of usage– Edges from decision or object nodes– Output parameter sets
• Rate: Stereotype added to activity edge to specify the number of objects and values that pass an edge at a given time interval– Special cases = Continuous and Discrete
April 10, 2023 41
Behavioral -Activities
Rate
Probability
Explicitly capture flow rates and
path probabilities
Versions of figure 11-11 & 11-12 in Submission Team spec v 0.98
April 10, 2023 42
Behavioral - Interactions
• Interactions– Describe interactions between
entities– Extends UML Timing Diagram
• Additionally represent properties and actions on the y-axis
• Additionally can mode continuous varying values
– Excludes Communication & Interaction Overview Diagrams
– Unknown Interoperability with Requirements Management Tools
• SysML interface with with standard requirement management tools unclear
April 10, 2023 53
Summary Assessment
• Advantages– Easy to understand with UML 2.0 knowledge– Easy to capture variety of system entities– Easy to document decisions in design– Increase data flow control mechanisms– Easy to do requirements modeling
• Limitations– Potential for diagram clutter– Potential for inconsistencies between views– Limited ability to model behavior across multiple scenarios in
one diagram– Unknown interoperability with requirements management
tools
April 10, 2023 54
Comments on the Submitted Spec
OMG & INCOSE Comments on the Spec• Good
– Reuse of UML 2– Timing & instance diagrams
• Issues– Missing “built from”
– Not reusing the same element in different views
– Lack of allocation
– Syntax rules unclear
– Specification hard to understand
April 10, 2023 55
More Information
April 10, 2023 56
Available SysML Modeling Tools
• ARTiSAN StudioARTiSAN Studio by by ARTiSAN Software
• SysML ToolkitSysML Toolkit by EmbeddedPlus • 3rd Party Plug-in to IMB Rational Suite
• OMG’s UML for Systems Engineering RFP– www.omg.org/cgi-bin/doc?ad/2003-3-41
• UML Resource Page – www.uml.org
April 10, 2023 60
Backup
April 10, 2023 61
Use Existing OMG Specs
Proposals may build upon the following specifications
• Unified Modeling Language (UML) v1.4 & 1.5
• Meta Object Facility (MOF) v.1.4– Framework for management and
interchange of UML models
– XMI Metadata Interchange v1.2 & 2.0
– UML Human-Usable Textual Notation (HUTN)
• UML 2.0• UML Profiles & Business Process
& Rules
The UML spec is the foundation of the SysML
spec
MOF
SysMLSysML
UML & Profiles
?
April 10, 2023 62
Spec Evaluation Criteria
• To be used by submitters and provide guidance to the evaluators
• Apply to solutions as a whole. Not to each individual requirement
• Ease of use• Unambiguous• Precise• Complete• Scalable• Adaptable to different domains• Evolvable• Capable of model interchange• Capable of diagram
interchange• Process and method
independent• Compliant with the UML
metamodel• Verifiable
April 10, 2023 63
OMG Adoption Process1. RFPs are drafted
• Written by OMG members• Presented to the appropriate Task Force (TF)
2. RFPs are issued by a Technology Committee (TC)• Upon the recommendation of the TF & the Architecture Board (AB)
3. Submitting organization provides a Letter of Intent to the OMG• Signifies a willingness to comply to the OMG’s terms and conditions • A member organization must be a member of the TC that issued the RFP
4. OMG members register to vote to select a specification
5. Initial submissions, revisions, and revised submissions are reviewed
6. TF evaluates final submissions
7. Registered OMG members vote to select a submission • Result is a recommendation to adopt a specification to the TC
8. AB reviews the proposal for MDA compliance and technical merit
9. TC votes to recommend adoption to the OMG Board of Directors (BoD)
April 10, 2023 64
OMG Adoption Process (2)10. OMG Board of Directors vote
• Resulting draft standard called “Adopted Specification”
11. Submitting members complete BoD Business Committee Questionnaire • Details how to use the specification in products • If no organization commits to use the standard, then the BoD will not act
adopt the standard.”
12. Finalization Task Force (FTF) is charted • Prepares the adopted submission for publishing as a formal, publicly
available specification• Ensures standard is implementable• Produces prototype implementations
13. FTF recommends adoption of the draft standard, called the “Available Specification”
14. TC recommends adoption to the Board of Directors• Board of Directors votes and accepts the specification
15.15. OMG publishes the formal specification OMG publishes the formal specification 16. Revision Task Force manages issues filed against the specification
April 10, 2023 65
OMG’s Business Committee Requirements
• There must be neither technical, legal nor commercial obstacles to [technologies] implementation.”
• Looks for commitment by submitter to the commercial success of products • Looks for evidence that each major feature has been implemented
– “Preferably more than once and by separate organizations”
• Should demonstrate cross-platform availability & interoperability• Must show that products based on the spec are commercially available or
will be within 12 months– If the submitter is not a commercial SW provider, BC requires evidence of 2 or
more independent implementations of the specification
• Will not adopt a spec if an intellectual property right infringement will occur• Must grant OMG worldwide, royalty-free license of the submitted
specification• Must show a commitment to support the specification & supporting
technology
April 10, 2023 66
Requirements Resolution Matrix
• Each proposal must include a matrix explain how it satisfied the requirements– Full, Partial, or No Solution
• Accomplished using:– UML construct without modification– UML construct with modification– Extension mechanism to define a new UML modeling element– Other approach
• Reference to the satisfying syntax• Reference to samples problem that demonstrates
satisfaction• Issues & comments
Many mandatory requirements
may be satisfied by the existing
UML spec.
April 10, 2023 67
Goals of RFP Evaluation
• Fair and open process• Facilitate critical review of the
submissions by OMG members• Provide feedback to submitters to
allow them to address concerns in revised submissions
• Build consensus on acceptable solutions
• Enable voting members to make an informed selection decision