abstract: Multi-tenancy architecture (MTA) is often used in Software-as-a-Service (SaaS) and the central idea is that multiple tenant applications can be developed using compo nents stored in the SaaS infrastructure. Recently, MTA has been extended where a tenant application can have its own sub-tenants as the tenant application acts like a SaaS infrastructure. In other words, MTA is extended to STA (Sub-Tenancy Architecture ). In STA, each tenant application not only need to develop its own functionalities, but also need to prepare an infrastructure to allow its sub-tenants to develop customized applications. This dissertation formulates eight models for STA, and proposes a Variant Point based customization model to help tenants and sub tenants customize tenant and sub-tenant applications. In addition, this dissertation introduces Crowd- sourcing to become the core of STA component development life cycle. To discover fit tenant developers or components to help building and com posing new components, dynamic and static ranking models are proposed. Further, rank computation architecture is presented to deal with the case when the number of tenants and components becomes huge. At last, an experiment is performed to prove rank models and the rank computation architecture work as design. / Dissertation/Thesis / Doctoral Dissertation Computer Science 2017