CFD General Notation System
Extensions

CGNS Proposals for Extension (CPEX)

The CPEX is a design document or documents that describe a new feature for CGNS. The CPEX should provide a concise technical specification of the feature and a rationale for the feature. The CPEX is intended to be the primary mechanism for proposing new features and for collecting community input on an issue. The CPEX author is responsible for building consensus within the community and documenting dissenting opinions.

The CPEX editors assign CPEX numbers and change their status. All CPEX-related email should be posted to cgnstalk. Each CPEX must have a champion - someone who writes the CPEX, shepherds the discussions, and attempts to build community consensus around the idea. The CPEX champion must first try to determine if their idea is appropriate for a CPEX. (Small enhancements or patches may not need a CPEX.) If a CPEX is appropriate, the champion must write a proposal, following the guidelines below. A CPEX number is then assigned. This is typically followed by a period of discussion, comments, input, and consensus-building, as well as an in-depth critical review. The CGNS Steering Committee ultimately votes for or against adoption.

The proposals listed in the table below that were "not accepted" never made it to implementation, possibly because of lack of unified support, incomplete details, lack of champion involvement in the process, or because they were not generalizable to a wide enough class of problems. It is possible to resurrect and/or revise and resubmit older proposals. Some additional guidelines regarding changes or additions to the CGNS standard can be found in the CGNS Steering Committee Charter.

The CPEX should include the following informaion:

• Name(s) and organization(s) of proposer(s)
• E-mail contact information
• General description of extension
• Reason or need for extension
• Detailed description of extension using similar documentation style found in the SIDS (LaTeX files for the SIDS are available from the Documentation Home Page - look for "LaTeX Source")
• File Mapping description of Node Attributes, following the prescription given in existing Node Description Documentation
• Specific example(s) of extension

In the table below, note that it is possible for a feature to be implemented in the SIDS and Filemap documentation, but not yet be implemented in the MLL software. If/when this occurs, it means that an "official" CGNS file can still be constructed with this feature, but the user must make use of means other than the MLL to accomplish it.

A primary requirement of all proposals for modifications will be to support and maintain code compatibility. No additions or changes to the CGNS standard will be adopted - without overwhelmingly compelling reasons - which invalidate existing software or data.

Note that the above CPEX work flow and requirements are new as of 09/2009, so older proposals given in the table below may be missing some of the required information.

Comments on proposals should be posted to cgnstalk.