Five interfaces of the workflow engine

The workflow reference model determines the basic architecture of the workflow management system. This architecture is a system model that should be adopted when developing workflow software. Of course, a workflow management system may not follow this model standard or only implement part of this model. However, it turns out that, this model structure is currently the most reasonable.

The core part of the system is the workflow engine, which is the main component driving process flow. It is responsible for interpreting workflow flow definitions, creating and initializing process instances, and controlling the flow path, record the process running status, suspend or wake up the process, terminate the running process, and communicate with other engines. WfMC does not provide specific standards for engine implementation, because too many constraints on the engine do not have much practical significance.

A workflow management system can contain one or more engines and provide five functional services externally through APIS. These functions are:

· Interface 1-Import and Export of Process Definitions
· Interface 2-same client applicationProgramInteraction with the work list Handler
· Interface 3-software tools and application calls
· Interface 4-collaboration between different workflow management systems
· Interface 5-management and monitoring functions

Through these five interfaces, the workflow management system can interact with external software tools. These tools can be provided by the same vendor or by different vendors, but the premise is that these tools must follow the WfMC specifications. You can also have sufficient options to decide the product of the vendor or the tool that develops the interface on your own.
These five interfaces are generally provided to users or software developers in the form of APIs. These APIs are called WAPI (workflow API), and some vendors encapsulate the APIS as components, to simplify development, reduce costs, and improve efficiency.

The following figure shows the functions of these five interfaces: