Workflow-driven Multi-tenant SaaS: Customization Middleware and Quality Implications

This thesis aims at providing customization middleware for workflow-driven multi-tenant Software-as-a-Service (SaaS) applications. A Multi-tenant SaaS application allows sharing a single instance of the application to be shared amont multiple customer organizations, a.k.a. tenants. Since tenants have (slightly) different requirements, the multi-tenant SaaS applications should be highly customizable. In specific case of workflow-driven applications, customization takes place both at the level of workflow definition and workflow activities. The highly customizability requirement brings new and challenging issues for existing workflow technologies which should be dealt with either complementary middleware or upgrading these technologies for the cloud age. This requires high-quality middleware design aiming at optimal scalability, performance, security and maintenance-cost consequences.