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Practical Experience
with Software Evolution
in Statoil ASA
SEVO Seminar, 16 March 2006
Odd Petter N. Slyngstad and Anita Gupta, Practical Experience with Software Evolution in Statoil ASA, SEVO Seminar 16.03.2006
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Overview
™ Two studies at Statoil ASA
™ Context and Contribution
™ Study#1: Investigation of Software Reuse
™ Research Questions and Hypotheses
™ Analysis and Results
™ Discussion
™ Study#2: Survey on Developers’ views on Software Reuse
™ Survey set-up
™ Research Questions
™ Results from the Survey
™ Ongoing and Future Work
Odd Petter N. Slyngstad and Anita Gupta, Practical Experience with Software Evolution in Statoil ASA, SEVO Seminar 16.03.2006
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Context and Contribution
™ Context:
™ Statoil ASA is a large Oil & Gas company, has ~24000
employees worldwide, represented in 28 countries
™ Contribution:
™ Better understanding and management of software
evolution
™ Goal: Possible to use results as baseline for comparison
Odd Petter N. Slyngstad and Anita Gupta, Practical Experience with Software Evolution in Statoil ASA, SEVO Seminar 16.03.2006
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Investigation of Software Reuse:
Study Objects, Research Questions,
Hypotheses and Results
™ Study Objects: Change Requests (202 CR’s) and Trouble
Reports (223 TR’s) for 6 of 7 reusable JEF (Java Enterprise
Framework) components (ranging in size from 268 SLOC to
8885 SLOC), over three releases.
Odd Petter N. Slyngstad and Anita Gupta, Practical Experience with Software Evolution in Statoil ASA, SEVO Seminar 16.03.2006
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Investigation of Software Reuse:
Research Questions, Hypotheses and Results
™ Research Questions:
™ RQ1: How does defect-density in reusable components
evolve over time?
™ H10: The defect-density in JEF components do not
change with time
™ H1A: There is a difference in defect-density for JEF
components over time
™ Result: ANOVA analysis resulted in the null hypothesis
being rejected, hence there is a significant difference in
defect-density for JEF components over time.
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Investigation of Software Reuse:
Research Questions, Hypotheses and Results
™ RQ2: How does the change-density for reusable
components (stability) evolve over time?
™ H20: The change-density in JEF components does not
change with time
™ H2A: There is a difference in the change-density for
JEF components over time
™ Result: ANOVA analysis proved inconclusive here, so we
cannot reject null hypothesis here. However, the data trend
is nevertheless declining change-density for most of the
components.
Odd Petter N. Slyngstad and Anita Gupta, Practical Experience with Software Evolution in Statoil ASA, SEVO Seminar 16.03.2006
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Investigation of Software Reuse:
Discussion of results
™ Quality attributes (defect-density and changedensity) can be used to partially characterize
evolution, as they show how the quality of the
reusable JEF components evolves over time:
™ Defect-density: Analysis indicates decreasing defect-density
over time for most of the components
™ Change-density: Unable to conclude without further analysis
™ Lower defect-density over time indicates an increased level
of achieved quality for the reusable components. Changedensity (stability) is important to achieve stable evolution of
the components and resources assigned to adapt/perfect
the reusable components
Odd Petter N. Slyngstad and Anita Gupta, Practical Experience with Software Evolution in Statoil ASA, SEVO Seminar 16.03.2006
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Survey on Developers’ Views on
Software Reuse: Survey set-up
™ Questionnaire design:
™ 30 Questions, 11 pages, 5 sections, 12-14 min. fill-in time.
™ Survey performed with short qualitative follow-up
interviews.
™ Respondents were all developers involved with the
DCF and S&A development projects, as well as
those on the JEF team, 16 in total.
Odd Petter N. Slyngstad and Anita Gupta, Practical Experience with Software Evolution in Statoil ASA, SEVO Seminar 16.03.2006
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Survey on Developers’ Views on
Software Reuse: Results (1)
™ RQ1: What are the key benefits of reuse?
™ Result: Lower development costs, shorter development
time, higher component quality as well as standardized
architecture seen as benefits of reuse.
™ RQ2: Which factors contribute to facilitate reuse?
™ Result: Improved documentation through information
repository could be beneficial.
™ RQ3: Does reuse increase rework?
™ Result: Inconclusive, we can show no link between reuse
and rework.
Odd Petter N. Slyngstad and Anita Gupta, Practical Experience with Software Evolution in Statoil ASA, SEVO Seminar 16.03.2006
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Survey on Developers’ Views on
Software Reuse: Results (2)
™ RQ4: Do developers have sufficient information to
understand the relevant components? If the answer
is no, how can they solve this problem?
™ Result: Most developers have sufficient information, but
documentation should be improved.
™ RQ5: Do developers trust the relevant quality
specification of the components? If the answer is
no, how can they solve this problem?
™ Result: Quality specification not trusted for reusable
components – should be improved.
Odd Petter N. Slyngstad and Anita Gupta, Practical Experience with Software Evolution in Statoil ASA, SEVO Seminar 16.03.2006
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Survey on Developers’ Views on Software
Reuse: Discussion
™ The promise of CBSE is the management of software
evolution through software reuse, hence it is important to
investigate the software reuse practices.
™ The results show that while significant benefits are seen
from software reuse, improvements in documentation and
quality specifications of the reusable components need to
be made. Also, reuse does not appear to have a link to
rework.
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Ongoing and Future Work
™ In-depth analysis of change-request data related to
the JEF components, on trends related to software
evolution.
Odd Petter N. Slyngstad and Anita Gupta, Practical Experience with Software Evolution in Statoil ASA, SEVO Seminar 16.03.2006
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Questions and Comments?
oslyngst@idi.ntnu.no
anitaash@idi.ntnu.no
www.idi.ntnu.no/grupper/su/sevo/
Odd Petter N. Slyngstad and Anita Gupta, Practical Experience with Software Evolution in Statoil ASA, SEVO Seminar 16.03.2006