Model View Definition (MVD) - An Introduction
What is an MVD?
In general, a MVD, or "Model View Definition", is a selection of entities of the overall IFC schema to describe facilitate a specific use or workflow. MVDs can be as broad as nearly the entire schema (e.g. for archiving a project) or as specific as a couple object types and associated data (e.g. for pricing a curtain wall system).
To support BIM interoperability across hundreds of software applications, industry domains, and regions worldwide, the IFC schema is designed to accommodate many different configurations and levels of detail. For example, a wall can be represented:
- as a line (or curve) segment between two points;
- as one of many types of 3D geometry for visualization and analysis (such as extruded solids or triangulated surfaces);
- as simple forms or with specific construction detail (capturing individual studs, pipe fittings, wiring, etc.)...
...along with data such as engineering properties, responsible party, scheduling, and cost information. But not every domain expert in the design, procurement, fabrication, and operations processes of a project need all the same information delivered or received.
Due to the large scope, IFC is not implemented in software. IFC is the large set of agreements; an MVD uses entities from IFC to define an exchange standard for a specific use-case or workflow. This exchange standard (MVD) is being implemented by Software Vendors.
Because an MVD is being implemented by Software Vendors, MVDs are the base against which the Software Certification takes place. Software implementations are checked against the requirements of an MVD.
An architect is sending a simple model to the client to place within a larger urban context model, allowing the client to visualize the design, the architect does not need to send all the complex modeling operations data (e.g. CSG) and object attributes, but can send a simple surface-based geometry model with simple color or texture mapping.
Precast manufacturers define how they want to receive IFC data. They define the use of assemblies, and that they need to have precise geometry represented with BREPs. Additionally they define what properties Precast elements should have.
Who supports MVDs?
All software applications that support the export of BIM data via IFC have some kind of MVD support. Typically, a BIM-authoring tool will have a list of MVD options in their IFC export user interfaces. Depending on the type of BIM tool, the MVD support will differ because of the domain the application serves, such as space planning, architectural, structural, or building system MVDs.
MVDs can be created in several ways. Separate publications of an MVD (like COBie) documentation package are often seen, but the use of mvdXML is also an option.
An overview of known MVDs can be found in our MVD database.
Future of MVDs
For a long time, everyone could create their own MVD and approach software vendors to implement it. This created a situation with several MVDs that have been created are not interoperable with each other, and need additional efforts for implementation in Software tools. Therefore IFC 4.3.x will have a few base MVDs that are defined by buildingSMART as a base for multiple use-cases.
In IFC5, this will be further restricted to guarantee interoperability between different domains and software implementations of IFC. IFC5 will be modular with a shared base. The definition of exchange requirements will be done using Information Delivery Specifications (IDS). More on this on the Technical Roadmap page.