If digital preservation had an extension it most likely would be .DP
Unfortunately, it’s taken. Say hello to Digital Paper.
In the early 1990’s, folks started to share documents with each other through the their phone lines. The early internet, BBS, AOL, CompuServe and the like allowed people to share ideas through applications like Word/WordPerfect Documents. Most people had a copy of the popular software and that software could open documents from their competitors, but fonts were always a problem. Technically a font is software as well and needs a license to be used. Also printers at the time dictated what the document might look like when opened, so your document may look different on someone else’s computer. This lead to a few innovations in the software market Digital Paper.
The idea is simple, create a format which could be opened with a free viewer which includes all the parts to make it look and print just like it was intended to. You may have already guessed who the winner in this space tuned out to be, yes, the PDF format. You can’t tell the history of the PDF Format without mentioning others that tried their luck to be the leader in portable document formats . WordPerfect’s Envoy format was one, Common Ground Digital Paper was another.
No Hands Software which started in 1990, developed the idea of making your documents truly portable. They released the Common Ground Maker and Viewer software in 1993. By 1996 the company was doing so well they were bought for $6 million by Hummingbird Ltd. PDF soon became so ubiquitous, formats like Common Ground and Envoy fizzled out. That doesn’t mean they didn’t have a big impact and still can be found in quite a few places.
Apple was one of the bigger users for awhile, but the format can still be found floating around today.
The Common Ground Digital Paper has some similarities to the PDF format, but the biggest different is the format is proprietary and not open like PDF. Another difference is you could embed the viewer into the file, this would make an executable on both Windows and Macintosh. Very convenient for sending to those who may not have the viewer or can’t install the viewer on their system.
Common Ground had two different viewers, a pro viewer with more features and a Mini Viewer with basic features and which was free to download and distribute from their website. Unfortunately, they linked to an FTP site which no longer is available and so finding the viewers today can be difficult.
I came across a boxed version 1 for Macintosh of the software a few years back, but have yet to find other full versions. The software did change hands a bit, but seems to have topped out at Version 4 in the late 1990’s. Let’s take a look at the file format for the samples we do have.
Version 1 for the Macintosh was the first I believe, coming to Windows shortly afterwards. The format was even assigned a MimeType for use on the web and the application gives us a little insight into the format.
The commonground file format does have versions (two at the moment). They *are* internally documented with a file signature, allowing commonground viewers to automatically handle both old and new format files. Therefore, I don’t believe a ‘version’ parameter is needed.
A Content-Type of “application/commonground” indicates a document in the Common Ground portable file format, also known as Digital Paper.
Encoding considerations: Common Ground files are in a binary format. Some encoding will be necessary for MIME mailers as in application/octet-stream. Common Ground files for the Macintosh are encoded in the data fork of a Macintosh file. The file type is APPL, the creator is CGVM.
If we look at a sample from Version 1 for the Macintosh we find the follow hex values:
hexdump -C CG-s01.dp | head 00000000 00 00 03 56 00 00 04 d9 43 47 44 43 00 00 00 00 |...V....CGDC....| 00000010 96 6c 00 07 04 b4 03 de 00 00 00 00 02 da 02 28 |.l.............(| 00000020 00 11 02 ff 0c 00 ff ff ff ff 00 00 00 00 00 00 |................| 00000030 00 00 02 28 00 00 02 da 00 00 00 00 00 00 00 01 |...(............| 00000040 00 0a 00 05 00 05 00 15 02 23 00 32 00 05 80 02 |.........#.2....| 00000050 00 15 7f fe 00 2c 00 09 00 03 06 47 65 6e 65 76 |.....,.....Genev| 00000060 61 00 00 03 00 03 00 0d 00 0c 00 2e 00 04 00 00 |a...............| 00000070 00 00 00 2b 06 11 07 54 65 73 74 69 6e 67 00 01 |...+...Testing..| 00000080 00 0a ff e1 ff e2 02 f9 02 46 00 03 00 00 00 0d |.........F......| 00000090 00 00 00 28 02 d5 01 05 05 2d 20 31 20 2d 00 ff |...(.....- 1 -..|
In all the samples I have the first 8 bytes are not consistent, but the next four bytes are. CGDC, which happens to be the registered type on the Macintosh. Convenient. But it appears later versions are not the same.
hexdump -C MANUAL.DP | head
00000000 00 00 00 20 00 00 b7 f4 44 50 4c 33 00 00 00 04 |... ....DPL3....|
00000010 00 00 00 00 00 00 00 00 3b 60 53 df 00 00 00 00 |........;`S.....|
00000020 00 00 00 18 00 00 b4 da 00 00 b4 c2 00 00 03 3e |...............>|
00000030 78 00 79 00 7a 00 7b 00 00 00 00 77 01 01 00 0c |x.y.z.{....w....|
00000040 00 01 02 01 00 00 00 97 fe ed f0 05 00 b7 86 04 |................|
00000050 5f 05 f7 01 00 03 ed f0 02 00 3d 00 ff 45 75 72 |_.........=..Eur|
00000060 6c 20 00 01 07 ff bf 05 9f 00 01 08 a3 05 fb ba |l ..............|
00000070 02 fa f1 00 ff ff 00 11 ff 68 74 74 70 3a 2f 2f |.........http://|
00000080 77 ff 77 77 2e 47 53 50 2e 43 b9 43 1c 0f 03 04 |w.ww.GSP.C.C....|
00000090 95 05 c8 0d 00 cc fb 05 e3 13 06 15 6d 61 69 6c |............mail|
hexdump -C dpwhite.dp | head
00000000 00 00 00 18 00 01 79 17 44 50 4c 32 00 00 00 00 |......y.DPL2....|
00000010 00 00 00 00 00 00 00 00 00 00 00 18 00 01 76 de |..............v.|
00000020 00 01 76 c6 00 00 04 b2 00 00 00 00 00 00 00 00 |..v.............|
00000030 00 00 00 1e 01 01 00 0c 00 00 01 01 00 00 00 12 |................|
00000040 00 01 00 01 00 00 00 00 0c 4e 09 60 01 2c 01 2c |.........N.`.,.,|
00000050 00 64 00 00 00 02 00 00 00 00 00 a2 01 01 00 0c |.d..............|
00000060 00 01 02 01 00 00 00 e2 fa ed f0 22 ed f1 0c 4e |..........."...N|
00000070 09 60 00 ff e1 01 26 0a 83 08 3b ff ff 6a ff 6a |.`....&...;..j.j|
00000080 0c e4 09 f6 01 ff 2c 01 2c 00 08 00 64 00 df 00 |......,.,...d...|
00000090 01 01 00 03 ed f0 0f 00 79 0a 1c 0f 28 07 42 41 |........y...(.BA|
These files are from a later version and have a different string at byte 8. DPL2 & DPL3. In the MiniViewer you can request document information and it provides some basic metadata for each file.
I only have one example of the DPL3, but a couple examples of DPL2, and it seems like DPL2 comes from a Version 3 DP Maker and DPL3 comes from Version 4 Maker. Need to see if I can find a Version 2 file and see if it follows the same pattern.
Two of my favorite CD-ROM’s on Internet Archive are Dr. Dobb’s The Essential Books on File Formats and Internet File Formats, both have copies of the Mini Viewer.
One of features similar to PDF is the ability to password protect certain features. This is what the document information looks like.
The header is the same, but the plain text usually seen in the file is no longer visible, so it appears the rest of the file is encrypted.
hexdump -C password.dp | head 00000000 00 00 5d 95 00 00 06 94 43 47 44 43 00 00 00 01 |..].....CGDC....| 00000010 8e 3b 18 7e c5 16 f8 e0 0f f5 6f 32 2f 34 36 81 |.;.~......o2/46.| 00000020 4b 8a 03 da 9e 1a 85 6c 36 e4 39 f2 5a 2a a2 5f |K......l6.9.Z*._| 00000030 81 83 65 ee 9c 16 d0 2d 2d c3 04 df 69 c8 06 0d |..e....--...i...| 00000040 77 df 27 19 33 59 f6 05 61 4e 2c a6 58 27 47 26 |w.'.3Y..aN,.X'G&| 00000050 fe 6b 3c 06 7e cb 7f fb 33 f8 64 ed 05 54 b4 7d |.k<.~...3.d..T.}| 00000060 c7 b5 e3 c2 df 40 53 63 ef 8e 10 1c c7 58 bd 28 |.....@Sc.....X.(| 00000070 9b 8a 2c 8f ae 82 33 f7 ff d4 3c 96 5c b4 08 69 |..,...3...<.\..i| 00000080 1f 00 af ce a7 56 93 27 07 cc 39 97 17 22 49 d7 |.....V.'..9.."I.| 00000090 5b 89 9b e6 b7 b1 5c 38 75 ba 08 ee 66 d0 9a d2 |[.....\8u...f...|
This file format is not currently in PRONOM. From what I have gathered I could add three signatures. There could be some other variations out there and the password protection needs to be considered. Maybe I’ll take Nick Gault’s offer and request the format which was available starting in the middle of 1995. Think they’ll deliver?