1. The Extensible Tool-chain for Evaluation of Architectural Models
12/3/2018
The Extensible Tool-chain for Evaluation of Architectural Models
George Edwards
Center for Systems and Software Engineering
University of Southern California

2. Presentation Outline Introduction and Background Project Overview
12/3/2018
Presentation Outline
Introduction and Background
Architecture Description Languages
Model-Driven Engineering
Project Overview
Goals and Approach
XTEAM
Extensible Modeling Environment
Model Interpreter Framework
Scenario-Driven Dynamic Analysis
Key Capabilities
Ongoing and Future Work
December 3, 2018

3. Background - ADLs Architecture Description Languages (ADLs)
12/3/2018
Background - ADLs
Architecture Description Languages (ADLs)
Capabilities:
Capture crucial design decisions
Can be leveraged throughout the software development process
Shortcomings:
Rely on rigid formalisms
Focus on structural elements
Lack support for domain-specific extensibility
Chart is taken from Medvidovic et al., A Classification and Comparison Framework for Software Architecture Description Languages
December 3, 2018

4. Background - MDE Model-Driven Engineering (MDE)
12/3/2018
Background - MDE
Model-Driven Engineering (MDE)
Combines domain-specific modeling languages with model analyzers, transformers, and generators
Domain-Specific Modeling Languages (DSMLs)
Codify domain concepts and relationships as first-class modeling elements
Metamodels
define elements, relationships, views, and constraints
Model interpreters
leverage domain-specific models for analysis, generation, and transformation
December 3, 2018

5. 12/3/2018
Project Goals
Provide an extensible infrastructure to aid software architects…
…provide design rationale
“Using a peer-to-peer architectural style for System X will result in greater scalability.”
…weigh architectural trade-offs
“Increasing the reliability of Service Y will incur an increase in latency.”
…evaluate off-the-shelf component assemblies
“The set of components selected will meet system energy consumption requirements.”
…test and validate systems incrementally
“The prototype of Component Z is not behaving as expected.”
December 3, 2018

6. 12/3/2018
High-Level Approach
December 3, 2018

7. Application Simulations
12/3/2018
The XTEAM Tool-chain
XTEAM employs a metaprogrammable graphical modeling environment (GME)
XTEAM composes existing general-purpose ADLs: xADL Core (structures and types) and FSP (behavior)
GME configures a domain-specific modeling environment with the XTEAM ADL
Architecture models that conform to the XTEAM ADL are created
XTEAM implements a model interpreter framework
The XTEAM ADL is enhanced to capture domain-specific information
The XTEAM Model Interpreter Framework is utilized to implement simulation generators
Application simulations execute in the adevs discrete event simulation engine
Simulations operate on the information captured in ADL extensions to perform scenario-driven analysis
GME Metamodeling
Environment
GME
Metamodeling
Paradigm
GME Domain-Specific
Modeling Environment
XTEAM ADL
XTEAM Model
Interpreter
Framework
adevs
Simulation
Engine
XTEAM
Simulation
Generators
Application Simulations
XTEAM ADL
Metamodel
XTEAM
Architecture
Models
xADL
Structures
and Types
Finite
State
Processes
ADL
Extensions
Application
Architectures
Energy
Consumption
Analysis
Reliability
Analysis
End-to-end
Latency
Analysis
Memory
Usage
Analysis
Scenario-driven
Analysis
Results
December 3, 2018

8. 12/3/2018
Extensible Modeling Environment Capturing Domain-Specific Architectures
Key Challenges:
Development of ADLs is inherently difficult
Combining extensibility with formal semantics
Solution: Codify ADLs as metamodels
ADL composition enables the combination of constructs from multiple ADLs within a single model
ADL enhancement allows the definition of new, customized ADL constructs
Reuse of existing ADLs maximizes the potential for reuse of the tool infrastructure.
Incremental language extensions enable a specific architectural analysis technique.
December 3, 2018

9. Model Interpreter Framework Implementing Architectural Analyses
12/3/2018
Model Interpreter Framework Implementing Architectural Analyses
Key Challenge:
Implementation of semantic mappings is time-consuming and error prone
Solution: Utilize a model interpreter framework
Transforms architectural models into executable simulations
Provides empty “hook” methods that are implemented by the architect to perform analysis calculations and record measurements
XTEAM Simulation Generators
Generator
Information Required
Analysis Provided
Latency
task and process execution times
for each required interface, the response time for each invocation
Reliability
failure probabilities and recovery times
time and type of failures and an overall component reliability metric
Energy consumption
computational and communication energy costs
energy consumption of each host (remaining battery power) over time
Memory usage
memory required by each task
amount of memory being used on each host over time
December 3, 2018

10. Scenario-Driven Dynamic Analysis
12/3/2018
Scenario-Driven Dynamic Analysis
Allows the architect to rapidly investigate the consequences of design decisions in terms of their impact on non-functional properties
Results depend heavily on the environmental context (e.g., the load put on the system)
May contain elements of randomness and unpredictability (e.g., the timing of client requests)
The set of scenarios to be simulated should include high-risk situations and boundary conditions
December 3, 2018

11. 12/3/2018
Project Goals
Provide an extensible infrastructure to aid software architects…
…provide design rationale
“Using a peer-to-peer architectural style for System X will result in greater scalability.”
…weigh architectural trade-offs
“Increasing the reliability of Service Y will incur an increase in latency.”
…evaluate off-the-shelf component assemblies
“The set of components selected will meet system energy consumption requirements.”
…test and validate systems incrementally
“The prototype of Component Z is not behaving as expected.”
December 3, 2018

12. Providing Design Rationale
12/3/2018
Providing Design Rationale
Client-Server Architecture
Architects rely on intuition and experience to make important decisions early in the design phase
What architectural style to use
How to allocate functionality among subsystems
What types of connectors to use
XTEAM allows architects to rationalize such decisions with experimental evidence
Model confidence level: Low
Peer-to-peer
Architecture
Potential Workload
Comparison of latency 
P2P achieves greater scalability
December 3, 2018

13. Weighing Architectural Trade-offs
12/3/2018
Weighing Architectural Trade-offs
Nearly all architectural decisions come down to trade-offs between multiple desirable properties
Emphasis on one system property may yield diminishing returns
XTEAM allows architects to evaluate design alternatives in terms of their impact on multiple non-functional properties
Model confidence level: Medium
Decreases response time
Replication of components
Consumes more battery power
December 3, 2018

14. Evaluating COTS Assemblies
12/3/2018
Evaluating COTS Assemblies
Contemporary large-scale distributed systems contain numerous off-the-shelf components
Detailed information about the behaviors and properties of individual components may be known
Component assemblies may exhibit unforeseen behavior due to subtle interactions between constituent components
XTEAM allows an architect to determine the emergent properties of a composed system
Model confidence level: High
Determination of
emergent properties
Off-the-shelf components
Highly accurate parameterization
December 3, 2018

15. Incremental System Validation
12/3/2018
Incremental System Validation
Individual component implementations may become available in a piecemeal fashion
XTEAM allows architects to
Immediately incorporate component implementations into a simulated system, increasing the accuracy of analysis results
Rapidly test individual components in the context of a wide variety of operational scenarios
Model confidence level: High
Component
implementation
available
Invoke implementation from behavior model
Integrated simulation and test environment
December 3, 2018

16. Ongoing and Future Work
12/3/2018
Ongoing and Future Work
Evaluate XTEAM using a real-world security application that operates in an embedded, wireless environment
Collaboration with Bosch RTC
Integrate XTEAM with other complementary architecture-based development tools
DeSi (model interchange)
Prism-MW (code generation)
Mae (product line architectures)
Further define ways in which our approach can be integrated with widely-used architectural development processes
Architecture Trade-off Analysis Method (ATAM)
Prediction-Enabled Component Technology (PECT)
December 3, 2018