eferred to as legacy - were monolithic: they owned the data, didn't provide well-defined interfaces and internally controlled all workflow related to a functional area. A service provider's uniqueness often manifests itself through unique business processes. A workflow is a realization of this business process. New services The Ultimate Guide to Building and Delivering OSS/BSS require new workflows and changing to existing services often also requires workflow changes. These changes are very hard to make in a legacy OSS environment since changes are embedded with a single system and hard- coded for legacy services. This is a key reason why service providers kept adding new silos of systems for every new service. The key concept of a component-based architecture is externalization of this workflow capability. Specialized components handle workflow processing. These components also provide tools for flexible and configurable definition of workflows. A workflow component is configured with a particular instance of a workflow, e.g., provisioning of an IP-VPN or auto trouble ticket creation. The workflow component executes various steps in the workflow and calls upon other components (legacy systems and/or next-generation) to do various tasks. The workflow component integrates with other components via the well-defined interfaces. This concept also allows a component to participate and be re-used in multiple workflows. 3.5.4 Common Infrastructure Services The component-based architecture defines an environment in which some common infrastructure services are implemented outside the component. The rationale behind this is that each component developer doesn't have to implement infrastructure services, such as authentication and authorization, security, directory, persistence and transaction management. These services are implemented once and then leveraged by all components deployed on that infrastructure. These services also have well-defined interfaces such that component developers can leverage them as part of their