Not that anyone feels it is important today, but X11 is multi user graphical computing.
A display server can display anything any user connected to it wants to display.
Actual 90's era use cases:
Application server. One copy of 3D CAD, one database, 30 users all running on a beefy machine well up to the task.
Each ran via X talking to the app server. Admin was cake, data big model access was fast, no user could actually touch the data except through use of the program.
User having trouble, push a window onto my display. I fix it, close window.
Display wall, conferencing. Big wall display, multiple users display data on it, one management user handling windows, etc...
Display wall, many small displays, each running via workstation. App sends display data to all of them.
Distributed computing resources:
Once, just for fun, I had an application data shared via a machine running nfs, fonts served by another machine, yet another machine running the application, yet another handling window management, all displayed on yet another machine serving the display and taking input.
(BTW, it was possible to literally kill the window manager and launch a different one and the display would shift a bit and the user continued along still running their app, but now using a different window manager!)
User could click on an icon, all those machines contributed to the app experience. Was hard to tell the difference between that and it running all locally.
Why?
Linux user wanted to run CAD unavailable on Linux, was developer who wanted a Linux box. So I used X to push the whole experience to their machine and distributed it for fun once it was working well just to learn and really push things, frankly.
While running, it was hard to tell the Linux machine was not an expensive commercial Unix machine.
All that was over 10-T and 100-T ethernet BTW.
Well designed X applications, particularly those using the SGI GLX extensions ran very well on local LANs. Poorly designed ones were nowhere near the quality of experience.
That skill was expensive. I think this is a big part of why so many struggled with X. A browser, for example, would not be comparable, pretty terrible.
Displaying web pages sucked, yet modeling a freaking car was amazing!
At the time, the X implementation of multi user graphical computing allowed for these and other combinations of users, machines, displays and applications.
It was well thought out multi user graphical computing!
The users could be local, as in a multi head machine offering two sets of keyboard, mouse, display, or they could arrive over the network.
Same as the Unix it was built on top of.
I think that is what people really are trying to get at when they say "network transparency"
Not all these use, or the set of possible use cases X made possible, make sense today.
But, when it was done?
Nobody knew, so they made a system as capable and that employed the best ideas in multi user computing, so that it was all possible.
That's why people who got to understand and really use X appreciate it as we see them do today.
A display server can display anything any user connected to it wants to display.
Actual 90's era use cases:
Application server. One copy of 3D CAD, one database, 30 users all running on a beefy machine well up to the task.
Each ran via X talking to the app server. Admin was cake, data big model access was fast, no user could actually touch the data except through use of the program.
User having trouble, push a window onto my display. I fix it, close window.
Display wall, conferencing. Big wall display, multiple users display data on it, one management user handling windows, etc...
Display wall, many small displays, each running via workstation. App sends display data to all of them.
Distributed computing resources:
Once, just for fun, I had an application data shared via a machine running nfs, fonts served by another machine, yet another machine running the application, yet another handling window management, all displayed on yet another machine serving the display and taking input.
(BTW, it was possible to literally kill the window manager and launch a different one and the display would shift a bit and the user continued along still running their app, but now using a different window manager!)
User could click on an icon, all those machines contributed to the app experience. Was hard to tell the difference between that and it running all locally.
Why?
Linux user wanted to run CAD unavailable on Linux, was developer who wanted a Linux box. So I used X to push the whole experience to their machine and distributed it for fun once it was working well just to learn and really push things, frankly.
While running, it was hard to tell the Linux machine was not an expensive commercial Unix machine.
All that was over 10-T and 100-T ethernet BTW.
Well designed X applications, particularly those using the SGI GLX extensions ran very well on local LANs. Poorly designed ones were nowhere near the quality of experience.
That skill was expensive. I think this is a big part of why so many struggled with X. A browser, for example, would not be comparable, pretty terrible.
Displaying web pages sucked, yet modeling a freaking car was amazing!
At the time, the X implementation of multi user graphical computing allowed for these and other combinations of users, machines, displays and applications.
It was well thought out multi user graphical computing!
The users could be local, as in a multi head machine offering two sets of keyboard, mouse, display, or they could arrive over the network.
Same as the Unix it was built on top of.
I think that is what people really are trying to get at when they say "network transparency"
Not all these use, or the set of possible use cases X made possible, make sense today.
But, when it was done?
Nobody knew, so they made a system as capable and that employed the best ideas in multi user computing, so that it was all possible.
That's why people who got to understand and really use X appreciate it as we see them do today.