Work items are collected from one or more work item providers for presentation to a workflow participant. A work item provider is typically a workflow management system (“WFMS”), but other providers of work items might exist that generate work items and may or may not have their own local worklist. Multiple independent WFMS's of multiple types might provide work items to a universal worklist (“UWL”) service that integrates the work items from all of the providers. Additional integration might be provided between the UWL and work item providers, such as for controlling work item execution with a sub-workflow through an ad-hoc workflow engine. Additional integration provides for custom attributes. Each work item has a type that is used to determine handling for that work item. A universal work list service includes storage for work items, wherein a work item represents a task generated as part of a process flow. An engine supporting the UWL service might track item types for work items and might obtain attribute values for attributes of the work item according to the work item's type.