Relativity theory in Lojban
According to lai krtisfranks, this is how Lojban currently (as of the CLL) does it (for a given inertial frame of reference). Note that any line parallel to the x' line (such as the orange one and, notably/particularly, the x' line itself) is a line of simultaneity (ca). Any event in the region below the x' line (the region with the tight, purple, vertical stripes) is in the "past"/pu of the observer whose reference frame we are examining; any event in the region above the x' line (the region with the wide, blue, horizontal stripes) is in the "future"/ba of the observer. It is important to understand that all pastward timelike-separated (and lightlike-separated) events are in the "past" (for everyone, no matter what reference frame), but some spacelike-separated evens are also in this observer's particular "past" region; likewise for their "future" region; the events that are spacelike-separated can be apparently reordered so that they are simultaneous or even have their apparent order switched in some frames of reference (but nothing within the light-cone has this property, with strictness matching the strictness of what "within" means). This picture varies for each frame of reference. But it is representative of all of them in the broad strokes.
The maroon discs each are events (they are points, but they are depicted as larger for ease of visualization - also, the variations in the size of the discs is just the fault of the creator of the image and means nothing). The gold lines are for signals (with natural normalization of units). The vertical grey and black lines are observers who happen to share a frame of reference. The blue lines are the division between "past" and "future" according to non-Relativistic interpretation (for this pair of observers).
[There might be some issues with grammar and meaning in this subsection]
Use the above picture as a visual guide. Let the signal channel be snailmail, event A be the event of Grey sending notice that he got attacked by a bear, event b be the event of Black receiving the letter and sending back (instantaneously in this example) his condolences, and event C be the event of Grey receiving the communication of said condolences.
le mu'e la .grusi. cu jai gau benji lo xatra be fo le nu lo cribe la .grusi. cu gunta kei be'o goi xy xi pa la .xekri kei .goi tau .a'y cabna le mu'e la .xekri. cu co'e xi pa kei goi .a'y ma'i tu'a la .grusi. joi la .xekri. lu'u goi my
.i le mu'e la .grusi. cu co'e xi re kei goi tau by cabna le mu'e la .xekri. gau te benji xy xi pa gi'e jai gau benji lo xatra be fo le nu la
.xekri. cu kecti la .grusi. be'o goi xy xi re kei goi by ma'i my
.i le mu'e la .grusi. gau te benji xy xi re kei goi tau cy cabna le mu'e la .xekri. cu co'e xi ci kei goi cy ma'i my
.i by .e cy .e tau by .e tau cy balvi .a'y .e tau .a'y ma'i my .i .a'y .e tau .a'y purci by .e cy .e tau by .e tau cy ma'i my
.i cy .e tau cy balvi by .e tau by ma'i my .i by .e tau by purci cy .e tau cy ma'i my
.i .a'y .e tau .a'y purci by .e tau by ma'i my .i by .e tau by balvi .a'y .e tau .a'y ma'i my
.i tau .a'y boi by tcese di'au tu'a lo masno se'o'e mrilu co'e goi zy
.i by boi tau cy tcese .i to .a'y tcese tau by .i tau by tcese cy toi
.i tau .a'y calse .a'y di'au zy .i tau by calse by .i tau cy calse cy
.i tau .a'y purci temse cy .e tau by .e tau cy di'au zy .i cy .e tau by .e tau cy balvi temse tau .a'y
.i .a'y purci temse tau cy .e by .e cy .i tau cy .e by .e cy balvi temse .a'y
.i tau by purci temse tau cy .i tau cy balvi temse tau by
.i by purci temse cy .i cy balvi temse by