Virtual organizations are flexible organizations, dynamically built from components of existing organizations. There are many advantages to virtual organizations, yet they are rare because successful implementation of such a dynamic design requires a significant technology infrastructure and a complex organizational architecture. This article takes a design approach and proposes such a technology infrastructure based on electronic services, formal semantics, and multi-dimensional ontologies. Organizational components are formally described as services, and placed in multi-dimensional ontologies, not only to capture their structural components, but also their organizational goals and audiences. Such multi-dimensional ontologies are not only useful to describe and search for organizational components, but also to efficiently build larger components from existing units. The architecture is extended to include virtual communities, virtual transactions, and virtual social institutions. The impact of such an architecture on transaction efficiency, organizational flexibility and adaptation, power structure, individual privacy, and organizational dissent are discussed.