Embedding Workflow Engines

Software developers have observed that certain parts of their applications are more change-prone than others. For example, for product-centric applications such as those that determine premiums for insurance policies or rates for calling plans, the most dynamic elements are the business rules that govern how products and services are priced and promoted. Likewise, for process-centric applications that handle mortgage loans or manage collaborative, team-oriented projects, the most fluid aspect is the flow of information between humans, systems, and organizations. An increasingly important goal of software design lies in isolating the highly dynamic elements of software applications, and empowering non-technical, business users with tools to manage them. Rule engines have emerged as a technology that permits business experts to control and maintain pricing-centric applications by manipulating business rules, without any knowledge of the underlying source code. Similarly, workflow engines empower business experts to manage and adapt process-centric applications by simply manipulating process flow diagrams, without touching the software that manages and executes the processes. Process-oriented applications are partially ordered sequences of steps that execute over time. They are best implemented using a design principle called flow independence [1]. Each step in a flow independent application encodes specialized business logic, and is executed by a process actor (i.e., human, application, or an organization). The sequence of steps defines the process flow, and is subject to continual change and tuning by domain experts. Flow independent applications manifest a clear separation of concerns between business domain experts that program and maintain process flows at the macro-level, and software developers that program and maintain each sequence step at the micro-level. This separation of concerns yields significantly greater responsiveness to changing business requirements; the high-level application logic or the “macro-program” can be re-wired by business domain experts using graphical process management tools without depending on software developers. At the same time, each individual step or “micro-program” can be modeled as a context-free, reusable service, because they have little or no awareness of the process flows that invoke them. The astute reader will note the similarity between flow independent design and service-oriented architectures that are currently taking hold in the world of Web Services. This article targets developers who are either considering embedding a workflow engine, or should be. It provides a narrative on how Openpages, a software vendor that develops and markets business applications for compliance and document management, selected a workflow engine for