  Recently, assurance cases have received much attentions in the field of
software-based computer systems and IT services. However, software very often
changes and there are no strong regulations for software. These facts are main
two challenges to be addressed in software assurance cases. We propose a
development method of assurance cases by means of continuous revision at every
stage of the system lifecycle, including in-operation and service recovery in
failure cases. The quality of dependability arguments are improved by multiple
stakeholders who check with each other. This paper reported our experience of
the proposed method in a case of the ASPEN education service. The case study
demonstrate that the continuos updates create a significant amount of active
risk communications between stakeholders. This gives us a promising perspective
for the long-term improvement of service dependability with the lifecycle
assurance cases.
