Many thanks to those who have replied to my posting. I wonder if I may add further information in the hope of satisfactorily responding to the comments made and also in the hope of encouraging interest in the idea of the classification system.
The classification system is intended to be quite straightforward to use. It does not necessarily need to be taken up by large manufacturers at all in order to be successful. As far as I can tell, a few software tools such as a competent programmer might fairly easily produce are all that would be needed in order to get the system into use. I am presently aware of four uses, or intended uses, of the Private Use Area. There may well be others, of which I am interested to learn. The four of which I am aware are as follows. The ConScript registry. Development of a character set for Egyptian hieroglyphics. Development of a character set for Cuneiform tablets. The eutocode system, which is part of my own research, which is mentioned in the DVB-MHP (Digital Video Broadcasting - Multimedia Home Platform) section at http://www.users.globalnet.co.uk/~ngo which is our family webspace in England. Within my classification system, suppose please that someone developing the character codes for Egyptian hieroglyphics requests that he or she be assigned type tray 3001 and that someone developing character codes for cuneiform requests the assignment of type tray C001 and that I request type tray E001 for the eutocode system, and that all of these requests are granted. Then, in order to apply the classification system to any plain text file, the file needs to contain some classification characters near the start. For a file using the Egyptian hieroglyphics characters, the following sequence would be needed. U+F35B U+F333 U+F330 U+F330 U+F331 U+F35D For a file using the cuneiform characters, the following sequence would be needed. U+F35B U+F343 U+F330 U+F330 U+F331 U+F35D For a file using eutocode, the following sequence would be needed. U+F35B U+F345 U+F330 U+F330 U+F331 U+F35D Suppose then that one day someone comes across a plain text file and within that plain text file are character codes from the Private Use Area and that person has no idea as to which character set those character codes may be intended to represent. So, the person looks at that file using a word processing program and chooses to use a specially made fount named findpuac.ttf (that is, the find private use area classification fount) which has all characters as zero width except for the eighteen characters in the U+F3.. block which I mentioned in my previous posting, those eighteen characters being implemented in the findpuac.ttf fount as having analysis glyphs as detailed in my previous posting. The screen display gives a code of C001 which the person can look up in a web based reference list and there finds out that it is in fact a particular character set for cuneiform characters. The web based reference list contains a link to a website from which the person downloads a copy of a special fount that contains the cuneiform characters. The plain text file is then displayed using that fount. That fount has the eighteen characters in the U+F3.. block which I mentioned as being zero width, so that they do not affect the display at all when the file is displayed. So, I suggest that the system is not too complex at all to implement and use. The findpuac.ttf fount would be needed. I do not have the knowledge or facilities to make that fount at present, yet as there are people who do have fount generation packages and they can make founts with characters in the Private Use Area, I feel that a findpuac.ttf fount, whilst being work that would need to be done and it all takes time and may cost money, is nevertheless not a goal the achievement of which seems prohibitively difficult. For the people producing the founts of Egyptian hieroglyphics characters and cuneiform characters, there is the additional work of making eighteen characters in the U+F3.. block as being of zero width, doing whatever needs to be done so that those eighteen characters do not display as rectangles indicating an unknown character. I do not know how to do that at present, yet it does not seem a prohibitively difficult thing to get done. For people producing a plain text file that includes the six character sequence of classification codes there could be some problems. These could be solved in practice by one of a number of methods. One method would be starting off each user generated file by editing a file that contains the six characters followed by an asterisk, so that the typist could add the Egyptian hieroglyphics or cuneiform characters after the asterisk, then delete the asterisk character using one push of the backspace key. Another method would be to have a software tool that takes an ordinary plain text file as input and produces a plain text file that is six characters longer, having had the six classification characters added in at the start of the new file. I suggest that in an environment where plain text files for various projects with various character sets are being used, that this classification system is straightforward and relatively easy to get implemented and potentially very useful. Please bear in mind that the production of the findpuac.ttf fount is a process that need only be done once by someone somewhere. Maybe someone reading this posting and who has the necessary facilities might even make one up and make it available: all of the information that is needed about the eighteen characters is included in these two postings. Once the findpuac.ttf fount were made, a word processor package such as Microsoft Word could be used to carry out the analysis on a PC. This classification system also allows characters from two different Private Use Area character sets to be included in the same file. For example, for research on cuneiform tablets, a cuneiform character set could be used to display characters and the data entry characters from eutocode (U+EC00 through to U+EFFF each load their ten least significant bits into an accumulator of a calculating engine) and the data movement and marshalling characters from eutocode (some codes from U+EB00 through to U+EBFF are used for such purposes) could be used to store three-dimensional measurement information (to 20 bits or 30 bits precision, or whatever is required) of the character's physical shape in a particular tablet of clay that is under consideration. Naturally, if the cuneiform characters are promoted then using two different uses of the Private Use Area in the same plain text file may no longer be necessary, yet the classification scheme would have perhaps served a valuable purpose on an interim basis. This is important. It is often the case that in order to get things achieved at a finished level that one needs to carry out development as best one can with the facilities that one has available. In hindsight, early experiments can look primitive, yet they are often an important step without which the finished result could not, or would not, have been achieved. Whilst I like to hope that many people will wish to use this classification system, in fact I do not need the agreement of anyone in order to get the system started as the Unicode specification includes, in relation to the Private Use Area, an implied right to publish character assignments. Publication does not need the agreement of anyone. However, I feel that it is important to try to gain a consensus and thus invite readers to comment on the idea. I am hopeful that this classification system will become widely used and will provide a useful optional additional facility for people who make use of the Private Use Area. William Overington 27 April 2002