What is OMS?

OMS is a development and runtime environment to efficiently create and run models from reusable components. OMS supports the model development/application lifecycle.

The Object Modeling System OMS is a modular modelling framework that uses an open source software approach to enable all members of the scientific community to address collaboratively the many complex issues associated with the design, development, and application of distributed hydrological and environmental models. Implementation of a common modular concept is not a trivial task. However, it brings the resources of a larger community to bear on the problems of distributed modelling, provides a framework in which to compare alternative modeling approaches objectively, and provides a means of sharing the latest modelling advances.

The Object Modeling System OMS is also an extensible and open software system. It is a

collection of software tools, which can be plugged together into an open modeling platform. This targets customized and flexible modeling support and reflects the requirement for an open and extensible model development and application framework.

The OMS architecture can be described as a layered architecture, it utilizes the NetBeans Desktop Application Framework. This architecture allows a very flexible customization of desktop application based on specific user requirements. For example a model software code developer needs for example access to compiler, a database access tool and a visualization package. Therefore the usage of a compiler/debugger components, a database component and a visualization component is required.

In other cases, an OMS user just wants to run a pre-built model without the need to change any of its code structure, but parameterize the model by editing input data. A model execution runtime component is therefore the one and only component is this case. Such components are named modules. Modules are extending the functionality of the framework by providing custom support for different aspects of model development and application.

Component based Modeling

Components are the main building blocks of simulation models in OMS. This chapter introduces the process of developing components with respect to their structure and behavior using development tools in OMS. In Section 1, an introduction to General component concepts, discusses the details of OMS components with respect to the API, and introduces tools within OMS to support and accelerate the development of components.

Traditionally, scientific applications are designed as large blocks of hand-crafted code, which usually builds a monolithic application. Such model applications are not designed to have parts of them easily re purposed if a related application will be required in the future. A major disadvantage of building monolithic simulation models is that conceptual boundaries within the model are captured or not there at all.

The term Component refers to a concept in software development which extends the re usability of code from the source level to the executable. Components are software units that are context-independent both in the conceptual and technical domain. A component is a self contained software unit that is well separated from its environment.

The component approach takes object-oriented designs to the next level. While object-oriented design methods focus on abstraction, encapsulation, and localization of data and methods, they can also lead to simulation systems where objects are highly co-dependent. To remove this limitation, a more rigid idea was introduced in model development using the Object Modeling System (OMS): component oriented modeling. It emphasizes the component as an object-oriented software unit which can be developed and tested independently, and finally delivered as a unit. It provides its services through well defined interfaces.

Component implementations in general are proven to support reuse in a more efficient way than just using object-oriented methods. There are some general benefits of using components for building complex systems.

1. Components are designed with a standard, well defined interface in mind. Such a published interface hides the implementation of the component logic and forces an abstraction level which separates the offered contract for communication from its implementation.
2. Components are self contained units from the conceptual and technical perspective. They can be developed and tested individually. Finally they are packaged and are delivered to be used in several applications.
3. The use of components simplifies the construction of complex systems since they change the way these are built. In contrast to programming all parts of a new simulation model from scratch, it can be composed using components. Not all parts of a new model can be just composed, component adaptation may be required. But a significant amount of work can be accomplished by component adaptation.
4. The use of components helps facing the challenge building complex simulation models by reducing model software complexity and by overcoming the limitations of monolithic, highly coupled model implementations. The Object Modeling System (OMS) promotes the application of components as fundamental building blocks. This chapter discusses the details of components to be used in an OMS model and introduces the supporting tools for their creation and management in OMS.