A workflow consists of a collection of coordinated tasks designed to carry out a well-defined complex process, such as catalog ordering, trip planning, or a business process in an enterprise. Scheduling of workflows is a problem of finding a correct execution sequence for the workflow tasks, i.e., execution that obeys the constraints that embody the business logic of the workflow. Research on workflow scheduling has largely concentrated on temporal constraints, which specify correct ordering of tasks. Approaches in this area are typically based on Temporal Logic, Petri Nets, and Concurrent Transaction Logic. Another important class of constraints --- those that arise from resource allocation -- has received relatively little attention in workflow modeling. Examples of such resources include physical objects, like workshop devices that a task might need in order to accomplish its goal, or intangible resources, such as time and budget. Since typically resources are not limitless and cannot be shared, scheduling of a workflow execution involves decisions as to which resources to use and when. In this work, a framework for scheduling workflows whose correctness is given by a set of resource allocation constraints is presented. This framework integrates Concurrent Transaction Logic (CTR) with constraint logic programming (CLP), yielding a new logical formalism, which is called Concurrent Constraint Transaction Logic (CCTR).