Example of an OPUS Configuration for UrbanSim - Emme/2 Interface

An example of an existing configuration will make this clearer. The psrc_parcel.xml file (note: not all browsers will render an XML file properly - to view the attached file you may need to download it and view it with an appropriate editor) contains all the information needed to configure the land use models in UrbanSim, and the hand-shaking with Emme/2 via file transfers in specified years. The OPUS run management system can be launched with this configuration and a reference to a scenario within it (e.g. Baseline_Scenario) and will launch the UrbanSim models, and when indicated, the Emme/2 models, for whatever years are specified in the scenario. Note that this is a worst-case for interfacing models: they do not communicate directly, they only read and write data that the other needs. Current infrastructure would support this for the proposed model system, but it is quite likely we can make this more efficient by how we design the APIs for the models, and how we pass data among them. So consider this example one that is only to document a point of departure.

We anticipate that some models will need tighter coupling than others. For example, MALTA and TrAM will interoperate tightly, and AMOS and MALTA will have minute by minute (simulated time) handshaking. The configuration of these interactions can be specified in XML, extending the configuration information now in OPUS to address these. This can include information on the convergence thresholds and other arguments used to manage the operation of the interacting models. It is also worth noting that OPUS configurations could be set up for any combination of these models. For example, one could configure a model set that did not include UrbanSim, and only the travel model components, for doing a short-term application. Or one could turn off the real estate developer model in UrbanSim but still allow households and jobs to relocate within a year for a similar configuration. All of this flexibility should be available if we adopt a uniform XML - based configuration approach that extends the infrastructure already implemented in OPUS.

-- PaulWaddell - 12 Nov 2009