How to enforce the left-to-right node ordering in GraphViz rank layout?

Question

I am visualizing a collection of process with GraphViz. Each process consists of some Read or Write operations in program order. Naturally, it is desirable to arrange the op

Answer 1

    digraph G 
{
ranksep = 1.0; size = "10,10";
{ 
    node [shape = plaintext, fontsize = 20];
    0 -> 1 -> 2 -> 3 -> 4;
}
node [shape = box];
{
rank = same;
0->wy1->rf1->rc1->rz1->ry1->ra1->rb1->rx2 [color=white];
rankdir=LR;
}
{
rank = same;
1->wf1[color=white];
rankdir=LR
}
{
rank = same;
2->wx2->wc1[color=white];
rankdir=LR;
}
{
rank = same;
3->wf2->wz2->wx3->wa1[color=white];
rankdir=LR;
}
{
rank = same;
4->wz1->wy2->wx5->wb1[color=white];
rankdir=LR;
}
wy1 -> rf1;
rf1 -> rc1;
rc1 -> rz1;
rz1 -> ry1;
ry1 -> ra1;
ra1 -> rb1;
rb1 -> rx2;
wx2 -> wc1;
wf2 -> wz2;
wz2 -> wx3;
wx3 -> wa1;
wz1 -> wy2;
wy2 -> wx5;
wx5 -> wb1;
wf1 -> rf1[color = blue];
wc1 -> rc1[color = blue];
wz1 -> rz1[color = blue];
wy1 -> ry1[color = blue];
wa1 -> ra1[color = blue];
wb1 -> rb1[color = blue];
wx2 -> rx2[color = blue];

// W'WR Order:
wx3 -> wx2[style = dashed, color = red];

// W'WR Order:
wx5 -> wx2[style = dashed, color = red];
}

I am not quite sure that i've correctly got your problem, but try using this and comment please if it is what you want. I've added invisible edges for correct ranking of nodes and used rankdir to use left-right layout.