Combining STEP, JAVA and Mapping gives user control of data

Currently EPM's EXPRESS Data Manager's (EDM) data can be accessed via the EDMI/SDAI API (Application Programming Interface) which is implemented as a late C or early C++ binding. Within the Esprit Vega (Virtual Enterprises using Groupware tools and distributed Architectures) project, TNO has developed a late Java-binding on top of the existing C-binding. This set of Java interfaces can be imported and called directly from any Java program or applet for accessing an EDM database.

In addition TNO has developed a "Java Generator" in Java on top of this Java-binding. This Generator generates for any EXPRESS Schema (available as meta-data in EDM) a set of Java Interfaces, Classes and generic functionality, which can be directly used within Java Applications. The generated Java can be seen as an early binding (in the Vega demo: an early "IAI IFC-1.5 Binding") on top of the generic late Java-binding. Not surprisingly, the core generated functionality has to do with instantiating and accessing the EDM Database. In this case even the Java-binding for SDAI is completely hidden for the Java end-developer and he can concentrate on his application's semantics assuming full persistency service from EDM.

In the Vega project we have shown how the generated Java code is utilized in its turn for browsing building product data which is defined by IAI's IFC1.5 EXPRESS schema. In addition we have shown how client-server technology (Java's RMI) can be utilized so that this browsing can be done over the Internet. The complete architecture for application of the Java Tools within Esprit Vega is depicted in Figure 1.

EDM's SDAI Services include:

• EXPRESS Compilation
• SDAI Repository/DB
• STEP read/write capability
• EXPRESS-X conversion
• Validation

In Vega the integration platform is a distributed version of ISO STEP SDAI: COrba Access to STep (COAST) which was developed by Digital. EPM provides a STEP SDAI Service on top of it. The generated Java classes are reused by the "IfcBrowser" demo-application, which resides mainly on the server and has its (manual) GUI-part on the client-side. The client code is a Java Applet, which is interpreted by Sun's Java Plug-in. The native Internet Explorer's Java Virtual Machine is currently not powerful enough to support Sun's latest JDK 1.1.6 and SWING 1.0.3. The links between the EPM's SDAI C-Binding, the Java Binding and the Java Generator (and its generated code) are detailed in Figure 2. First, the SDAI C Library is linked via JNI (Java Native Interface) to the Java versions of the SDAI-functions and the necessary functions (EDMI) not within scope of SDAI like Database I/O. The Java Binding is further imported by both the Generator and the Generated Code for transparent access to the data and meta-data in EDM. It should be clear that this is just one application of the Java Tools. In general these tools can be used to make any EDM data accessible on a higher abstraction level than SDAI to the Java developer especially for the development of client-server Internet applications.

Other TNO activities in Vega

Besides the Java developments, TNO is applying EPM's EXPRESS Data Manager in two other tasks within Vega:-

• Integration of a Heat Loss Program (by VABI)
• Integration of ISO STEP AP225 / VRML-visualization

Both items involve semantic integration where EXPRESS schemas are mapped according to an EXPRESS-X specification. Based on these specifications, EPM's EXPRESS-X tool generates fully automatic converters to map IFC1.5 data to VABI resp. AP225 data. In the latter case the target data is visualized via a VRML-generator developed by the French CSTB. This generator is currently re-engineered to also work on top of the Java Binding and code generated by the Java Generator.

The Future of Java in EDM

After the Vega project has finished (end 1998), the Java Binding and Java Generator will be further developed and commercialized by EPM. Both components will be integrated in the existing EDM product line. This means that an end- developer can, besides the EDMI/SDAI C or C++ bindings also utilize the EDMI/SDAI Java-binding. Moreover he can generate from the EDM Supervisor Java Interfaces and Classes for all his EXPRESS schemata which will further increase his productivity in application development, especially in client-server configurations. Beta demo-versions of both Java Binding & Java Generator will be available later this year. Products like these are seen as key steps in the further integration of STEP and Internet technologies.

For more information please contact: Michel Böhms (H.Bohms@bouw.tno.nl) or Johan van der Waal (J.vanderWaal@bouw.tno.nl) of TNO or Jorulv Rangnes (Jorulv.Rangnes@epmtech.jotne.com) of EPM.