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Profiles
The transfer of graphical file formats between applications and between machines has caused many users a great deal of frustration. It often "doesn't work". This may be because the software used does not use the file format in the same way. This may be for a number of reasons which include:
• the software may have implemented the specification incorrectly
• the format specification may be ambiguous and open to different interpretations
• the generating software and the interpreting software may have implemented different subsets of the format specifications and thus some parts of the file may not be understood on interpretation
For these (very common) reasons, there has been a move to create profiles (or application profiles as they are sometimes known) for file formats, or combinations of formats. This work has been progressing for some years for graphical file formats with work by MAP (Manufacturing Automation Protocol initiative led by General Motors), TOP (Technical Office Protocol initiative led by Boeing) and CALS (the US Department of Defense initiative). The CALS work has provided the major thrust in the production of profiles for some years and these have included vector and raster formats as well as formats for product data exchange and document formats.
The Computer Graphics Metafile standard has been extended to include the requirements for defining profiles and a pro forma and model profile to assist in the definition of profiles. Profiles are very useful because they can be used as the basis for conformance testing. Profiles for CGM are currently being used by the Air Transport Agency (ATA), the petroleum industry (through the PIP profile) and by CALS. International Standardized Profiles are also being developed for CGM through the European Workshop on Open Systems (EWOS) and these will be harmonised for international standardization. CGM profiles are being used to define a MIME type for use on the Internet and within the WWW.
Other standards are also adopting the profile concept. This is due to the comprehensive nature of standards which try and offer a wide range of facilities not always needed by all applications. The Image Interchange Facility (described below) also uses the concept of profiles.