The Architecture of S2

We present in this paper the essential aspects of the S2 system. This is the internet realization of SEMPER: An active, multi-domain, space-based, object oriented design environment for integrated building performance modeling. We begin with an overview of SEMPER principles. We then present the component based system architecture of S2, which makes use of the Common Object Request Broker Architecture (CORBA) for communication between components including our analysis applications (written in C++) and other S2 components (written in Java). We describe the underlying approach to and implementation of the shared object model. This serves as the shared building representation from which the analysis modules derive their domain object models using a homology-based mapping process. INTRODUCTION The key features of the S2 environment are as follows: A user can access the system regardless of the computer hardware, operating system or the location on a network; geographically distributed users can asynchronously generate a building model through the user interface; this building model can then be simultaneously accessed by multiple simulation applications running on remote simulation servers; persistent storage is provided for project data and evaluation results; designers using the system have access to multiple libraries that contain building information such as material data, construction types, schedules, and weather data. S2 is a reengineered version of SEMPER for the internet to support collaborative design scenarios. SEMPER is a multi-aspect prototype design environment that incorporates an object-oriented, space-based building model, with dynamic links to different building performance evaluation applications (Mahdavi 1996). It is thereby intended to computationally support the evaluation of buildings across multiple performance mandates concurrently, with a view toward achieving total building performance and systems integration. SEMPER incorporates the unique synthesis of four principles: 1. A methodologically consistent performance modeling approach through the entire building design process The performance simulation modules incorporated within SEMPER rely on a consistent (first-principles based) modeling of the physical processes relevant to the building’s performance. SEMPER currently includes modules for energy, air flow, HVAC, thermal comfort, lighting, acoustics, and life-cycle analysis. 2. Seamless and dynamic communication between the simulation model and the general building representation This provides "on-line" building performance feed-back to the user while eliminating the need for explicit definition and updating of the underlying simulation model. SEMPER exemplifies this by dynamically linking the building’s general representation (essentially a shared object model) with structurally homologous representations of the simulation modules (essentially the domain object models) (Mahdavi and Wong 1998, Mahdavi et al. 1997). Figure 1 illustrates, for example, the homology-based mapping from the shared building representation to the thermal and air flow simulation domains. The shared building representation embodies topological information on the architectural spaces and their relationships. The energy and air flow simulation modules utilize a spatial representation consisting of spatial units (cells) with nodes that define finite control volumes. These nodal representations of the building are configurationally homologous to and are directly derived from the space-based representation of the building in the shared object model. This homology-based mapping mechanism allows for rapid feedback and is therefore a powerful design instrument, since evolving building designs can be made subject to comprehensive parametric studies in multiple domains without