1. Make Software Modular. And… Efficient
Make Software Modular! And… Efficient? s An Empirical Evaluation of OSGi Dependencies Best Practices
Lina Ochoa, Thomas Degueule & Jurgen Vinju
Mining Software Repositories (MSR) 2018
S.W.A.T.

2. “Engineers are very pragmatic; they may admire beauty, but they seek utility. I tried to find an explanation of why “beauty” was useful.”
- David L. Parnas

3. Modularity in software
Modular software
Non-modular software

4. How modularity works in Java language?
- Java is one of the most popular programming languages (#1 acc. TIOBE 2018)

5. Modularity in Java + OSGi
OSGi document:
450 pages!
mod.sort
pkg.sort.api
pkg.sort.impl
mod.students
mod.math
pkg.math.api
pkg.math.impl
pkg.students.api
Bundle-ManifestVersion: 2
Bundle-Name: Lib1
Bundle-SymbolicName: a.lib1
Bundle-Version: release-2
Bundle-RequiredExecutionEnvironment: JavaSE-1.8
Export-Package: org.package1;version=“0.0.1”
Require-Bundle: a.lib2;bundle-version=“2.1.1”
Import-Package: org.package4;version=“[1.1,1.5]”
DynamicImport-Package: org.package5
Require-Bundle
pkg.students.impl
Import-Package

6. What OSGi best practices are advised?

7. OSGi best practices B1: Prefer package-level dependencies
B2: Minimize dependencies
B3: Export only needed packages
B4: Use versions when possible
B5: Import all needed packages
B6: Avoid dynamic import of packages
B7: Separate implementation, API, and OSGi-specific packages
B8: Use semantic versioning
B9: Avoid splitting packages
B10: Declare additional dependencies in the bundle classpath
B11: Import exported API packages

8. B1: Prefer package-level dependencies
mod.sort
pkg.sort.api
pkg.sort.impl
mod.students
mod.othersort
pkg.sort.api
pkg.sort.otherimpl
pkg.students.api
Require-Bundle
Import-Package
pkg.students.impl
Import-Package

9. Are OSGi best practices being followed?

10. Best practices in practice
372 modules B1
58% of the bundles use Require-Bundle. B2
83% of packages required through Require-Bundle are never used. B3
15% of exported packages are imported through Import-Package.
80% of exported packages are required through Require-Bundle.

11. Do OSGi best practices have an impact on the system efficiency?

12. Studied corpus C0 C6 C1 R6 R1 372 modules Corpora Results Benchmark
Transform
Compare
Benchmark C0 C6 C1 R6 R1
Results
Corpora …
372 modules
Rascal MPL

13. Best practices impact on…
Classpath size
Median relative difference: 0% – 23%
Resolution time
Median relative difference: ±13%

14. “I tried to find an explanation of why “beauty” was useful.”
- David L. Parnas

15. Make Software Modular. And… Efficient
Make Software Modular! And… Efficient? An Empirical Evaluation of OSGi Dependencies Best Practices (MSR 2018)
Lina Ochoa Thomas Degueule Jurgen Vinju
11 OSGi best practices
Best practices are not widely followed
Best practices impact on classpath size (0-23%) and performance (±13%)
“Modularity without regret.”