1. A Case Study of Variation Mechanism in an Industrial Product Line
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4th International Workshop on Bidirectional Transformation in Architecture-Based Component Composition
A Case Study of Variation Mechanism in an Industrial Product Line
Xin Peng
Fudan University
Published in ICSR 2009
joint work with Prof. Stan Jarzabek from National University of Singapore (NUS)

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Software Product Line
A software product line is a set of software-intensive systems sharing a common, managed set of features that satisfy the specific needs of a particular market segment or mission.
Paul Clements, SEI
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3. Motivation Realities of SPL practices in small companies
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Motivation
Realities of SPL practices in small companies
not employing any advanced variation mechanisms (e.g. AOP, FOP, XVCL...), only some simple mechanisms used
but it often works well with a very small SPL team
WFMS product variants used at over 100 universities in China: Fudan University, Shanghai Jiaotong University, Zhejiang University, Harbin Institute of Technology, …
Maintained by 1-2 developers and supported by more service engineers
Evolved for more than 6 years
Research problems
What mechanisms are used
How well do they work
What are the pros and cons
Are there any possible improvements
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4. WFMS Product Line (WFMS-PL)
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WFMS Product Line (WFMS-PL)
Wingsoft Financial Management System (WFMS)
a product line practice in a small company, Fudan Wingsoft Ltd
financial management for colleges and institutes: provide Web-based financial services for employees and students in
first developed in 2003 and evolved to an SPL with more than 100 customers
Tuition Management Subsystem (TMS)
A subsystems of WFMS
A web-based portal for students to pay online their tuition fee
20K LOCs Java code and other source files
25% source code of the whole system
representative types of variability and variation mechanisms
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5. TMS Feature Model 32 Variant Features 2019/7/21
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TMS Feature Model
32 Variant Features
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6. Variations in TMS Types of variant features
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Variations in TMS
Types of variant features
Fine-grained feature: affecting many system components, at many small variation points in implementation
Coarse-grained feature: usually including whole files into a customized product when the feature is selected
Mixed-grained feature: involving both fine- and coarse-grained impacts on implementation
Implementation Objects in TMS
Java source code (the most common configuration object)
Others: JSP (HTML) files, configuration files (XML), DB schema (SQL Scripts)
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7. Variation Mechanisms Used in TMS
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Variation Mechanisms Used in TMS
Five variation mechanisms
Conditional compilation & comments
Design patterns & reflection
Overloaded fields
Ant
Parameter configuration file
Number of features involved for each techniques
# Techniques
# Features
Conditional compilation & comments 31
Ant 19
Overloading fields 13
configuration items 12
Design Pattern & reflection 3
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8. Conditional Compilation & Comments
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Conditional Compilation & Comments
For fine-grained variation points
Java conditional compilation for Java source code files
Final-boolean mechanism in Java: if a final-boolean variable’s value is false, then the code in the statements under if is not compiled into the generated bytecode file and vice versa
Comments for non-java files
e.g., JSP files, SQL files
Example:
Conditional Compilation
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9. Design patterns & Reflection
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Design patterns & Reflection
Usually used with Reflection and other variation mechanisms (e.g., Ant)
Most used design patterns in TMS
AbstractFactory with FactoryMethod
Strategy
Example:
Strategy Pattern
with Reflection
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10. Overloaded Fields For the configuration in DB schema
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Overloaded Fields
For the configuration in DB schema
A table may have some general fields named spec_1, spec_2 ... spec_n
They can have different meanings in different product variants
E.g. the same field may be used to store bank card number in one product variant and ID card number in another one
Pros: several product share the same DB schema, not need to configure for specific product
Cons: hard to distinguish if too many product variants share the same field, error-prone
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11. Ant For coarse-grained feature configuration
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Ant
For coarse-grained feature configuration
The build tool can move needed files from core asset to product release directory
Example: configure DownloadPaymentDetail with Ant
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12. Parameter configuration file
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Parameter configuration file
Self-defined XML configuration file
Containing both data and control parameters
Can be combined with branching statements for variation implemention
Can also develop self-implemented tool to read the file and do configuration
e.g. generating the Ant configuration file
Example:
configuration file
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13. Summary of Variation Mechanisms for all the TMS Features
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Summary of Variation Mechanisms for all the TMS Features
- More than 80% features
(26 among 32) were managed by more than one variation mechanism
Design patterns/Configuration file/Ant were always used together with other mechanisms
- Almost all features involved the use of conditional compilation and/or commenting out feature code
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14. Summary of Variation Mechanism
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Summary of Variation Mechanism
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15. Evaluation of Feature Granularity
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Evaluation of Feature Granularity
Statistics for implementation-level variation points per granularity level
Fine-grained impacts caused most of the configuration problems
Problem: how to properly configure all fine-grained variation points for the same feature?
Introduced by bad modularization for variation implementation
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16. Evaluation of Traceability
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Evaluation of Traceability
Statistics for configuration points in example features
Traceability
Each feature may be addressed at many variation points scattered through many SPL core components
Problem: how to find and analyze the code at all these variation points?
A SPL core component is usually affected by many features that may be managed by different possibly overlapping variation mechanisms
Problem: how to understand interactions among these mechanisms?
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17. Overall Evaluation Pros: Cons:
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Overall Evaluation
Pros:
Each mechanism is easy to learn and apply
No need for training, third party tools, etc
Cons:
Many variation points, in many components
Complex mappings: features-to-components
Using many mechanism together is not easy
Manual, tedious, error-prone customizations
Reuse and evolution of PLA is not easy
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Conclusion
Fundamental differences in capabilities of variation mechanisms justify the use of multiple variation mechanisms
Different variation mechanisms have different, often complementary strengths and weaknesses
Feature characteristics must be matched by the capabilities of variation mechanism (s) used to manage the feature
However, over time the inter-play between multiple variation mechanisms may become difficult to comprehend, configure and manage
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Thanks!
Q&A
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