NexJ Model Server Express Server is a an open source [http://java.sun.com/javaee/ Java EE-based] execution server software which specialized to enterprise integration applications. It provides cost effective services for deploying highly-scalable, fault -tolerant, distributed enterprise solutions. It encapsulates the key NexJ Model Server Express provides:   * Business Object Engine - supports a single-inheritance class structure as well as aspects of the [http://www.nexj.com/application_framework.aspx NexJ Application Framework] to provide specific application characteristics beyond * Workflow Engine - persistent, long-running asynchronous UML activities that are initiated by and enables the advanced act on business logicclass instances* Persistence Engine - model multiple data sources (relational, XML) in a database-independent way, connect to multiple data sources at runtime leveraging different database connectivity, advanced workflow adapters* Integration Engine - model message-based communication between the running model and rules, rich integration, other systems supporting multiple protocols and enhanced data message formats* Security Engine - design privilege-based security that are model and apply throughout the other model layers   NexJ's approach to model-driven engineering (MDE) using the model-execution capabilities of NexJ Model Server Express greatly simplifies the hallmarks process of all solutions that are configured using developing enterprise applications. Using NexJ Express Studio, developers focus solving the business problems while the NexJ Framework handles technical complexities of running that solution.