Software Architecture Recovery: The 5 Questions You Always Asked Yourself About,

The 5 questions you always asked yourself about

Software Architecture

Recovery

Mircea LunguFaculty of Informatics, University of Lugano

October 2008

Software Architecture Recovery - Mircea Lungu, 2008

5 Questions about SAR

• What is it?

• Why is it important?

• What is it?

• How does it work?

• What is it?

• Who does it?

• What is it?

• Who does it?

• Where is it headed?

• Architecture Recovery

• Architecture

• Viewpoints

Architecture recovery ...

Architecture recovery ...or Architecture Reconstruction,

or Reverse Architecting

[...] an archaeological activity where the analysts must unveil all the historical design decisions by looking at the existing implementation and documentation of the system.

[ Riva’00 ]

or Architecture Reconstruction,

or Reverse Architecting

... the flavor of reverse engineering that concerns all activities for making existing of software architectures explicit.

[Krikhaar’97]

... the techniques and processes used to uncover a system’s architecture from available information.

[Jazayeri’00]

... the flavor of reverse engineering that concerns all activities for making existing of software architectures explicit.

[Krikhaar’97]

Architecture...

[...] the structure or structures of the system, which comprise software elements, the externally visible properties of those elements, and the relationships among them.

[Bass et al.’03]

Architecture...

[Bass et al.’03]

[...] the fundamental organization of a system, embodied in its components, their relationships to each other and the environment, and the principles governing its design and evolution.

[ANSI/IEEE Std. 1471-2000]

Architecture...

[Bass et al.’03]

[...] the fundamental organization of a system, embodied in its components, their relationships to each other and the environment, and the principles governing its design and evolution.

[ANSI/IEEE Std. 1471-2000]

For many others visit

www.sei.cmu.edu/architecture/definitions.html

What is the difference between architecture and

design?

Architectural Styles

Styles. Architectural styles such as pipes and filters, lay- ered system, data flow and blackboard are popular because like design patterns, they represent recurrent architectural situations [11, 59]. They are valuable, expressive, and ac-

cepted abstractions for SAR and more generally for software understanding.

Recognizing them is however a challenge because they span several architectural elements and can be implemented in

various ways [100, 101]. The question that turns up is whether SAR helps reverse engineers specify and extract architectural styles.

• Recurring architectural solutions

• Examples

• Pipes and filters

• Blackboard

• Peer-to-peer

• ... ... still, there are SAR approaches which take it into

consideration.

• Examples

• Blackboard

• Peer-to-peer

consideration.

• Examples

• Blackboard

• Peer-to-peer

consideration.

SAR is not preoccupied with recovering the architectural

style of the system.

Viewpoints

• Viewpoints catalogues

• Kruchten’95

• Hofmeister’99

• Ad-hoc viewpoints

• Smolander’01

• Conway’s law

Viewpoints

• Viewpoints catalogues

• Kruchten’95

• Hofmeister’99

• Ad-hoc viewpoints

• Smolander’01

• Conway’s lawMost of the SAR processes focus on

recovering component-and-connector viewpoints.

What is the relation between architecture recovery and reverse

engineering?

• Reasons

• Benefits

• Goals

• Challenges

Architecture erosion

[...] the documentation about the internal architecture becomes rapidly obsolete. To make changes, developers need a clear understanding of the underlying architecture of the products.

C. Riva, Software Architecture Group, Nokia Research

Architecture Evolution

One frequently accompanying property of evolution is an increasing brittleness of the system -- that is, an increasing resistance to change, or at least to changing gracefully.

[Perry & Wolf ’92]

Architecture Evolution

• Architectural drift

• Architectural erosion

• Architectural upgrade

One frequently accompanying property of evolution is an increasing brittleness of the system -- that is, an increasing resistance to change, or at least to changing gracefully.

[Perry & Wolf ’92]

Conceptual vs. As-is architecture

Software systems must evolve or become obsolete [...]

[Lehmann’80]

Architecture

Change In Environment

Architecture

CodeEnvironment

Change In Code

Change In Architecture

Change In Code

[Lehmann’80]

Architecture

CodeEnvironment

Change In Code

There is a need for enforcing the

architecture of a system

[Lehmann’80]

Architecture

CodeEnvironment

Change In Code

Architectural

Firewall

There is a need for enforcing the

architecture of a system

[Lehmann’80]

Consultant’s POV

• Missing architectural specifications

• Support the

• Re-documentation

• Reengineering

[...] Frequently we are asked to analyze a systemʼs software architecture and are given only its code and the (limited) time of a designer.

[Kazman et al.’99]

Benefits

• Stepping stone towards reengineering

• Supports detecting components for reuse

Challenges

• What process can support uncovering the software architecture within a system?

• How much can you automate in this process?

• What are the limits of architecture recovery? (e.g., Recovering all design decisions).

• Generic approach

• Processes

• Bottom-up

• Top-down

• Integrated

Phases of Reconstruction

Data Extraction Knowledge Organization

Information Exploration

[Tilley et al.’96]

Phases of Reconstruction

Data Extraction Knowledge Organization

Information Exploration

The Meta-Architecture of

Architecture Recovery Tools

[Tilley et al.’96]

Data Extraction

• Source Code (static analysis)

Data Extraction

• Historical Information

Data Extraction

• Human Expertise

Data Extraction

• Human Expertise

• Runtime Behavior (dynamic analysis)

Data Extraction

• Human Expertise

• Physical Organization

Data Extraction

• Human Expertise

• Physical Organization

• Social Organization

[Pollet et al.’07]

Facts extracted from code

[Guo et al.’99]

Knowledge Abstraction

• Get rid of useless information

• Aggregation

• Directory

• Packages

• Clustering

• Filtering

[Lungu et al.’05]

Processes

Software Architecture Recovery - Mircea Lungu, 2008 [Pollet et al.’07]

Processes

1. Bottom-up Approaches

• Start with low-level fact extraction

• Aggregate the information to higher abstraction levels either manually or automatically

Tools 4 bottom-up

• Arch• ArchView• ArcVis• ARMIN• BUNCH• DALI• Gupro• Intensive• Rigi• Softwarenaut

• Developed at Siemens Research

• Mavericks - individual procedures in the wrong modules

• Heuristic modularization advice

[Schwanke’91]

Archview

[Pinzger’05]

Archview

[Pinzger’05]

Lightweight Source Model Extraction (LSME), Imagix, make, and Perl for extraction of source model information for C and C++,

PostgreSQL (based on POSTGRES) for model storage,

Rigi, IAPR (Interactive Architecture Pattern Recognition) [12], RMTool [14], and Perl for analysis and manipulation.

Advertising break!

• Aggregation: based on directory structure, clustering, package structure

Advertising break!

• Filtering: based on evolutionary information, metrics

Advertising break!

• Filtering: based on evolutionary information, metrics

• Visualization: polymetric

Softwarenaut

2. Top-down approaches

• Start with previous high-level knowledge about the application domain

• Formulate hypotheses and verify them against the source code

Tools 4 top-down

• RMTool

• Pulse

• W4

Reflexion Models

Marco...

• Fraunhofer Institute for ESE

• Architecture- and Domain-Oriented Re-engineering

• Product Line Software Engineering

W4By distilling pearls of wisdom stored deep inside source control systems, we can assist developers to understand the state of their project and plan confidently for its future

[Hassan & Holt’04]

• Which, Who, Why, When

By distilling pearls of wisdom stored deep inside source control systems, we can assist developers to understand the state of their project and plan confidently for its future

[Hassan & Holt’04]

3. Hybrid Approaches

• Combine top-down with bottom-up

• Abstract low-level information

• Refine high-level information

Tools 4 hybrid

• Albortz

• ARM

• Bauhaus

• Cacophony

• DiscoTect

• ManSART

• PBS/SBS

• Symphony / Nimeta

ManSART

• Mitre Corporation

• Used to provide architecture level consulting in multiple military systems

ManSART

[Harris et al.’ 95]

Discotect

• Examine runtime behavior

• Big problem: abstraction gap

• State machines to map between implementation-level events and architectural operations

[Yan et al.’04]

• SEI at Carnegie Mellon

• Hasso-Plattner Institute

• Nokia Research Center

Case Study #1

• Author: CMU Software Engineering Institute

• Subject: VANISH, 50KLOC

• Tools: Dali, ARMIN

• Goals

• generate several architectural views

• determine if strict layering is in place

• Assumptions: little documentation, no developers available

#1: Results

Case Study #2• Author: Hasso-Plattner Institute

• Subject: Apache, 100KLOC C code

• Participants: 60 4th semester students

• 32 topics assigned

• Sources

• documentation (well written, little info about the conceptual architecture)

• “Writing Apache modules with Perl”

• Results: overview analysis, detailed state diagrams, memory management

• Time:: half a semester for getting accustomed with the domain and half for analyzing the implementation

#2: Results

www.fmc-modeling.org/category/projects/apache/amp/Apache_Modeling_ Project.html -

#2: Results

Case Study #3

• Author: Nokia Research

• System: Embedded Software Written in C

• Existing Reference Architecture

• Scripts that extract information about messages

#3: Results

Others

• “Linux as a Case Study, it’s Extracted Architecture”, Bowman et al.

• “Static evaluation of Software Architectures”, Knodel et al.

Where?

• Future of SAR

• Further Reading

The Future of SARThe Place of Architecture in a Crowdsourced

WorldRick Kazman

http://www.sei.cmu.edu/news-at-sei/columns/the_architect/architect.htm

The Future of SAR

• Integrating with forward engineering (continuous supervision, architectural firewalls, etc.)

The Place of Architecture in a Crowdsourced World

Rick Kazman

The Future of SAR

• Collaborative architecture recovery

Rick Kazman

The Future of SAR

• Product family architecture

Rick Kazman

The Future of SAR

• Product family architecture

• Ecosystem architecture

Rick Kazman

Software Architecture Recovery: The 5 Questions You Always Asked Yourself About,

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