Format Showing Data Exchange
Software incompatibility is the main hurdle that restricts the easy data sharing among two or more system. It happens because of the fact that supplier of the computer application might develop the design configuration for different priory format to store the data needed and its display. To ensure the compatibility for smooth data sharing, there is a requirement of neutral data exchange format. Here the term neutral refers to a format that might be easily exploited by several systems. Reasonably good data exchange format or standard or neutral file must satisfy a minimum set of requirement. These requirements are concerned along the common entities needed in different modeling system such like wire frame entity and surface entity etc. This is expected from a standard format that it should become compact and help in gaining faster data storage and retrieval. Some of the popular standards reported in the various books are PDES (Product Data Exchange Standards) and IGES (Initial Graphics Exchange Specification).
In the year of 1980s, the features of IGES were published and in subsequent years the same has been thoroughly updated. Among the dissimilar CAD/CAM system, the primary well known data exchange format was reported by IGES only. The same format has also been adopted to communicate the data among the manufacturer and the suppliers. Thus, it can be inferred that IGES helps to build up a communication interface among the different system.
Figure: CAD Systems with Electronic Data Transfer
Under the aegis of International Organization for Standardization (ISO), massive efforts have been pursued to build up an international standard known as STEP (Standard for Transfer and Exchange of Product Model Data). This refers to global standardization of exchange of information pertaining to the computer application in manufacturing. Features of STEP have been used to evolve another data exchange standard known as product data exchange, which has found broad ranging application for different kind of work in the industry. The major difference among IGES and PDES is that IGES utilizes entities (different kind of geometric entities, structure entities etc.) as basic element, while PDES data exchange is carried out in terms of application.
Operating mechanism of PDES is described by three layers. These are :
A. Application layer,
B. Logical layer, and
C. Physical layer.
The user and PDES are interfaced by the application layer, where application model is apparently defined and different types of information is expressed by using information modeling techniques. The major task of logical layer is to support faultless, consistent and computer independent description so that adequate information is available to encapsulate the broad range of applications. To maintain the structure & format of exchange file, the role of physical layer comes into picture to ably manage the magnitude of the file sizes.
Figure: CAD Systems with Context to Inter-Application Communication
Another format for data exchange has gain ground in recent years to assist in the interchange of drawings among AutoCAD and other program. This is known as DXF, which stands for Drawing Exchange File Format. This format is capable of implementing features of AutoCAD and also modified them into file representation. Majority of the software packages supports the DXF format & the ASCII test files also include DXF files.
Irrespective of data exchange systems, the common way through which drawing details are transferred electronically between the different CAD systems are described in above Figures.