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

The 5 questions you always asked yourself about

Software
Architecture
Recovery
Mircea Lungu
Faculty of Informatics,
University of Lugano

October 2008

5 Questions about SAR

Software Architecture Recovery - Mircea Lungu, 2008


• What is it?



• 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?


What?

• Architecture Recovery
• Architecture
• Viewpoints

Architecture recovery ...


or Architecture Reconstruction,


or Reverse Architecting


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 ]



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

[Krikhaar’97]



... the ﬂavor of reverse
engineering that ... the techniques and
concerns all activities for processes used to uncover
making existing of software a system’s architecture
architectures explicit. from available information.

[Jazayeri’00]
[Krikhaar’97]


Architecture...


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...
elements, the externally [...] the fundamental
visible properties of those organization of a system,
elements, and the embodied in its components,
relationships among them. their relationships to each
other and the environment, and the
[Bass et al.’03] principles governing its design and
evolution.

[ANSI/IEEE Std. 1471-2000]

Architecture... For many others
visit
www.sei.cmu.edu/architecture/
deﬁnitions.html
elements, the externally [...] the fundamental
visible properties of those organization of a system,
elements, and the embodied in its components,
relationships among them. their relationships to each
other and the environment, and the
[Bass et al.’03] principles governing its design and
evolution.

[ANSI/IEEE Std. 1471-2000]

What is the difference
between architecture and
design?


Architectural Styles

• Recurring architectural
solutions
• Examples
• Pipes and ﬁlters
• Blackboard
• Peer-to-peer
• ... a

Architectural Styles

• Recurring architectural
solutions
• Examples
• Pipes and ﬁlters
• Blackboard SAR is not preoccupied with
• Peer-to-peer recovering the architectural
• ... style of the system.
a

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 Most of the SAR processes focus on
• Conway’s law recovering component-and-
connector viewpoints.


What is the relation between
architecture recovery and reverse
engineering?


Why?

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

[Perry & Wolf ’92]


Conceptual vs. As-is
architecture
Software systems must
evolve or become
obsolete [...]

[Lehmann’80]


architecture
Change In
Environment
evolve or become
obsolete [...]
Change In
Code
Environment Code
[Lehmann’80]
Change In
Code

Architecture
Change In
Architecture

As-Is
Architecture


architecture
Change In
Environment
evolve or become
obsolete [...]
Change In
Code
Environment Code
[Lehmann’80]
Change In
Code

Change In
Architecture
Architecture
There is a need for
As-Is
Architecture
enforcing the
architecture of a
system

architecture
evolve or become
Architectural
Change In Firewall
Environment

obsolete [...]
Change In
Code
Environment Code
[Lehmann’80]
Change In
Code

Change In
Architecture
Architecture
There is a need for
enforcing the
architecture of a
system

Consultant’s POV

[...] Frequently we
are asked to analyze
• Missing architectural a systemʼs software
speciﬁcations architecture and are
• Support the given only its code
• Re-documentation and the (limited) time

• Reengineering 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).


How?

• Generic approach
• Processes
• Bottom-up
• Top-down
• Integrated

Phases of Reconstruction
Knowledge Information
Data Extraction
Organization Exploration

[Tilley et al.’96]

The Meta-
Phases of Reconstruction Architecture of
Architecture Recovery
Tools

Knowledge Information
Data Extraction
Organization Exploration

[Tilley et al.’96]

Data Extraction


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]

p

n
-u

w
om

do

d
ri
p-
tt

yb
Bo

To

H
Processes


p

n
-u

w
om

do

d
ri
p-
tt

yb
Bo

To

H
Processes

[Pollet et al.’07]

• Start with low-level fact
1. Bottom-up extraction
Approaches • 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

Arch

• Developed at Siemens Research
• Mavericks - individual procedures in the wrong
modules
• Heuristic modularization advice

[Schwanke’91]

Archview

[Pinzger’05]

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

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


Advertising break!


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


• Start with previous high-
2. Top-down level knowledge about the
application domain
approaches
• Formulate hypotheses and
verify them against the
source code


Tools 4 top-down

• RMTool
• Pulse
• W4


Reﬂexion Models

Marco...


Pulse

• Fraunhofer Institute for ESE
• Architecture- and Domain-Oriented Re-engineering
• Product Line Software Engineering


Pulse


W4
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]


W4
By distilling pearls of
wisdom stored deep inside
source control systems, we
can assist developers to
understand the state of
their project and plan
• Which,Who,Why,When conﬁdently for its future

[Hassan & Holt’04]


• Combine top-down with
3. Hybrid bottom-up

Approaches • 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]

Who?

• 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 -

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 SAR


The Future of SAR

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


The Future of SAR

• Collaborative architecture recovery


The Future of SAR

• Product family architecture


The Future of SAR

• Product family architecture
• Ecosystem architecture


Further Reading
• Annotated Bibliography
www.inf.unisi.ch/phd/lungu/recovery

• Essays on Architecture
http://www.sei.cmu.edu/architecture/essays.html

• PhD Theses: Pinzger’05, Krikhaar’99
• Survey Articles: Pollet’07


THE END


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