Workflow technology, which is characterized by extracting process logic from individual applications and manipulating it separately to achieve organization-wide business process integration and automation, asks for an appropriate infrastructure support and encourages new system architectural styles. This paper presents a framework for constructing workflow-based applications. Based on configurable models, software agents and business objects, the framework focuses on, in addition to supporting the basic requirements of workflow-based computing, the flexibility issues that are identified as a deficiency of many contemporary workflow systems. With the help of the framework, a workflow system can be more flexibly composed at runtime according to specific and changing needs.