Summary: I think Portable TeX Documents are a great idea. (Disclaimer: I'm the inventor.) Come to tomorrow's TeX Hour to discuss.
Date and time: Thursday 26 August, 6.30 to 7.30pm UK time.
UK time now: https://time.is/UK
Zoom URL: https://us02web.zoom.us/j/78551255396?pwd=cHdJN0pTTXRlRCtSd1lCTHpuWmNIUT09
Adobe released PostScript (PS) in 1982, and Portable Document Format (PDF) in 1993. Many production and user problems in PS were fixed in PDF, which remained a proprietary standard until 2008. PS and PDF were both based on very sound technical and business decisions. PDF so to speak created a safe and self-contained world for the distribution of typeset documents. PS and PDF are both page description languages.
In 1982 Don Knuth created a safe and self-contained world for typesetting that was rapidly adopted by mathematicians and physicists. It includes the DVI page description language. PDF arrived 11 years after TeX, and Sergey Lesenko's DVIPDF followed three years later.
TeX produces identical outputs, given identical inputs. PDF does something similar. It also has a structured storage system for storing fonts, graphics, multimedia objects and other resources. This allows PDF to guarantee identical inputs to its page description language.
I firmly believe that Portable TeX Documents (PTD) will greatly benefit TeX users and developers, just as PDF benefitted its users, developers and Adobe. As a loyal and responsible member of the TeX community, I feel obliged to share this opinion with the community, both promoting it and fairly considering objections and alternatives.
Here's a technical teaser. Each PTD has document and typesetting inputs, and optionally typesetting outputs. Every tree of files checked into git has a secure hash, which is unfeasible to forge. These secure hashes are keys that characterize the PTD, including its inputs and outputs.
Besides version control, git is very efficient at turning a secure hash into its tree of files, provided it has access to a repository that contains all files in the tree. All font metric and style files that have ever been uploaded to CTAN will occupy only a few gigabytes when stored in git, and most TeX documents will require perhaps only 50MB of such files.
So downloading on the fly resources required from the typesetting of a TeX source document is entirely practical. The source could be CTAN, or somewhere else. This is because git is a peer-to-peer distributed file system. Further, like a well set up website, git doesn't fetch resources it's already got.
One hard part of implementing PTD, besides getting resources and overcoming inertia, is specifying the exact form of the resource tree of a PTD. I hope that once that part is in practice solved others will use it. This will allow other parts of the standard to evolve. It took Abode 11 years to go from PostScript to PDF.
LAST WEEK'S VIDEOS
Last week's TeX Hour was on XML to (La)TeX to PDF. Digital Humanities met Mathematics and Physics. The videos are available at