Seidewitz_041513 - University of Maryland

UML: Once More with Meaning
University of Maryland
Model-Based System Engineering Colloquium
Ed Seidewitz
15 April 2013
Copyright © 2013 Ivar Jacobson International SA. All rights reserved
UML Prehistory: Object-Oriented Analysis and Design
• OOAD orthodoxy (c. 1980s): Organize programs to model the
basic concepts of the problem domain.
• Problem: Programming languages (even OOPLs) are not
particularly good as problem domain modeling languages.
– Too much of a program must focus on implementation details.
– As the program grows, the “big picture” gets lost.
• Solution: Use a graphical modeling notation for analysis and
– “Model the problem domain” during analysis.
– “Model the solution” in problem domain terms during design.
– Use the solution model as a “blueprint” for coding.
• Consequence: “Modeling” in the software community became
drawing pictures, for problem domain representation and solution
– Precise “meaning” was only to be found in the programs themselves.
Unified Modeling Language v1.x
Unified Modeling Language (UML) intended to “unify” the various
OOAD graphical modeling languages of the early 1990s.
1995 – UML 0.9 by Booch, Rumbaugh and Jacobson (“3 amigos”)
1996 – UML 1.0 proposed by Rational
1997 – UML 1.1 adopted by Object Management Group (OMG)
The intent of OMG standardization was primarily to allow syntactic
interchange of models between tools.
Unified Modeling Language v2.x
There was a hope to add semantic interoperability to the UML
standard with UML 2.
1999 – UML 2.0 Request for Information (RFI)
2000 – UML 2.0 Requests for Proposal (RFPs)
2003 – UML 2.0 Adopted
2005 – UML 2.0 Finalized
2011 – UML 2.4.1 Latest formal version
“However, the presence of numerous variation points in these
semantics (and the fact that they are defined informally using natural
language), make it impractical to define this as a formal compliance
type, since the number of possible combinations is very large.”
– UML Superstructure Specification, v2.0 – 2.4.1
Unified Modeling Language v2.5
The UML 2.5 specification document is reorganized to be
“consumable” and to remove redundancy and correct
inconsistencies. Primarily focused on semantics descriptions.
2008 – Future Development of UML RFI
2009 – UML Specification Simplification RFP (UML 2.5)
2012 – UML 2.5 Adopted
2013 – UML 2.5 Finalized (planned)
“A tool demonstrating semantic conformance provides a
demonstrable way to interpret UML semantics, e.g., code generation,
model execution, or semantic model analysis.”
– UML 2.5 Specification, Semantic Conformance
Foundational UML (fUML)
Foundational UML (fUML) is an executable subset of standard UML
that can be used to define, in an operational style, the structural and
behavioral semantics of systems.
1998 – Action Semantics for the UML RFP
2003 – UML 1.5 with action semantics formalized
2003 – UML 2.0 adopted
2005 – Semantics of a Foundational Subset for
Executable UML Models RFP
2008 – fUML 1.0 Beta (based on UML 2.2)
2010 – fUML 1.0 Formal (based on UML 2.3)
2012 – fUML 1.1 Beta (based on UML 2.4.1)
fUML Scope
The semantics of fUML provide the foundation for formally
specifying the (execution) semantics of the rest of UML.
Some areas of UML (e.g., use case and requirements
models) may not be best formalized based on an
executable semantics foundation.
Activity Model
State Machine
Foundational Semantics
Base Semantics
fUML operational semantics are
specified as an execution model
written in fUML itself.
The base semantics of the subset of
fUML used in the execution model are
specified using formal logic.
fUML Key Components
• Foundational UML Subset (fUML) – A computationally
complete subset of the abstract syntax of UML (Version 2.4.1)
– Kernel – Basic object-oriented capabilities
– Common Behavior – General behavior and asynchronous
– Activities – Activity modeling, including structured activities (but
not including variables, exceptions, swimlanes, streaming or other
“higher level” activity modeling)
• Execution Model – A model of the execution semantics of user
models within the fUML subset
• Foundational Model Library
– Primitive Types – Boolean, String, Integer, Unlimited Natural
– Primitive Behaviors – Boolean, String and Arithmetic Functions
– Basic Input/Output – Based on the concept of “Channels”
Action Language for fUML (Alf)
The Action Language for Foundational UML (Alf) is a textual surface
representation for UML modeling elements with the primary of acting
as the surface notation for specifying executable (fUML) behaviors
within an overall graphical UML model.
2008 – Concrete Syntax for a UML Action Language RFP
2010 – Alf 1.0 Beta (based on UML 2.4 and fUML 1.0)
2013 – Alf 1.0.1 Beta (based on UML 2.4.1 and fUML 1.1)
Alf Key Components
• Concrete Syntax – A BNF specification of the legal textual syntax
of the Alf language.
• Abstract Syntax – A MOF metamodel of the abstract syntax tree
that is synthesized during parsing of an Alf text, with additional
derived attributes and constraints that specify the static semantic
analysis of that text.
• Semantics – The semantics of Alf are defined by mapping the Alf
abstract syntax metamodel to the fUML abstract syntax metamodel.
• Standard Model Library
– From the fUML Foundational Model Library
• Primitive Types (plus Natural and Bit String)
• Primitive Behaviors (plus Bit String Functions and Sequence Functions)
• Basic Input/Output
– Collection Functions – Similar to OCL collection operations for
– Collection Classes – Set, Ordered Set, Bag, List, Queue, Deque, Map
Hybrid SUV Example: Operational States
A state machine abstracts
system behavior into a finite
number of states.
The system is modeled as
having discrete transitions
between the states.
A transition may trigger
further system behavior…
…or system behavior may
be dependent on the current
Using Alf to Define a State Machine Behavior
Hybrid SUV Example: “Accelerate” Activity
An activity specifies behavior
as the coordinated execution
of a set of subordinate
An action in one
activity may call
another activity.
Data and control
flow between the
various actions.
Hybrid SUV Example: “Provide Power” Activity
Other actions provide
various data and
computational functions.
Using Alf to Specify an Action
After a certain level of detail,
it is much more convenient to
use a textual rather than
graphical notation (whether
mathematical constraints or
procedural action language.)
Using Alf to Define an Activity (1)
Alf statements in the
body of an opaque
action may be compiled
into an activity.
The original Alf statements can
then be preserved in a
comment element stereotyped
as a «TextualRepresentation».
Using Alf to Define an Activity (2)
namespace ‘Hybrid SUV’;
private import Alf::Library::IntegerFunctions::Min;
activity ProportionPower(
in battCond: Integer, in accelPosition: Integer, in speed: Integer,
out eThrottle: Integer, out gThrottle: Integer, out transModeCmd: TransModeCommand) {
throttle = (accelPosition * battCond) / GetMaxBattLevel();
eThrottle = Min(throttle, GetMaxEThrottle());
gThrottle = Min(accelPosition - throttle, GetMaxGThrottle());
transModeCmd = new TransModeCommand();
transModeCmd.level = speed / GetTransModeConv();
The Goal: Automated Execution and Analysis
The Goal: Model Based System Engineering
Execution artifacts could include:
System behavior, timing and statistics
Using standard-based
model interchange
System engineers analyze, simulate and
validate the system design, and allocate
requirements to components.
create the
Using a standardconforming model
execution tools
Using standardconforming modeling
Models can include
both hardware and
software components.
• Hardware and software engineers develop
components to satisfy the requirements.
• Test engineers develop the test
environment to verify the requirements.
• fUML Implementations
– Open Source Reference Implementation
(Academic Free License 3.0)
– Cameo Simulation Toolkit for MagicDraw from NoMagic
– Advanced Modeling | UML Simulation and Execution (AM|USE)
by LieberLieber for Enterprise Architect from Sparx Systems
• Alf Implementations
– Open Source Reference Implementation
(GNU General Public License 3.0)
– Alf for Papyrus Eclipse UML Tool (Ongoing)
Ongoing Work
fUML Version 1.2
Alf Version 1.1
Precise Semantics of UML Composite Structures
Additional “Precise Semantics” RFPs
– State machines
– Interactions
– Complete activities/process modeling
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