For systems-of-systems, the use of different modeling methods is important not only because each system can be described more correctly, but also benefit from tools that are in use by different communities. Using an opaque or closed source-code tool with others, however, is challenging. Consequently, to facilitate the development of simulations for systems-of-systems it is useful to cast closed-source models in a flexible component-based framework. Using this concept, a RESTful web service framework is developed for the Water Evaluation And Planning (WEAP) software system. The WEAP RESTful framework has a suite of model components for all the model entities defined in the WEAP system. An example water system model shows the computational cost for the web-service framework is negligible. Casting the model entities to components can play a key role in using the WEAP system with other modeling frameworks useful for simulating the complexities of the Food-Energy-Water systems.