Definition and Optimizability of ngql sequential sentence

[czpmango]

My test:

(czp@nebula) [nba]> $var = GO FROM "Tim Duncan" OVER * yield like._dst as dst; order by $var.dst;$var1=go from $var.dst over like yield like._dst as dst1,$var.dst as dst2;order by $var.dst
+-----------------+
| dst             |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
| "Manu Ginobili" |
+-----------------+
| "Tony Parker"   |
+-----------------+
Got 7 rows (time spent 15030/16290 us)

(czp@nebula) [nba]> $var = GO FROM "Tim Duncan" OVER * yield like._dst as dst; order by $var.dst;$var1=go from $var.dst over like yield like._dst as dst1,$var.dst as dst2;match (v:player) return v;order by $var.dst
+-----------------+
| dst             |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
| "Manu Ginobili" |
+-----------------+
| "Tony Parker"   |
+-----------------+
Got 7 rows (time spent 47863/49124 us)

(czp@nebula) [nba]> $var = GO FROM "Tim Duncan" OVER * yield like._dst as dst; order by $var.dst;$var1=go from $var.dst over like yield like._dst as dst1,$var.dst as dst2|match (v:player) return v;order by $var.dst
+-----------------+
| dst             |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
|                 |
+-----------------+
| "Manu Ginobili" |
+-----------------+
| "Tony Parker"   |
+-----------------+
Got 7 rows (time spent 48728/49929 us)

(czp@nebula) [nba]> $var = GO FROM "Tim Duncan" OVER * yield like._dst as dst; order by $var.dst;$var1=go from $var.dst over like yield like._dst as dst1,$var.dst as dst2;go from $var1.dst1 over like yield like._dst as dst33, $var.dst
+-----------------+----------+
| dst33           | $var.dst |
+-----------------+----------+
| "Tim Duncan"    | __NULL__ |
+-----------------+----------+
| "Tony Parker"   | __NULL__ |
+-----------------+----------+
| "Manu Ginobili" | __NULL__ |
+-----------------+----------+
| "Manu Ginobili" | __NULL__ |
+-----------------+----------+
| "Tony Parker"   | __NULL__ |
+-----------------+----------+
| "Tony Parker"   | __NULL__ |
+-----------------+----------+
| "Tim Duncan"    | __NULL__ |
+-----------------+----------+
Got 7 rows (time spent 21976/23141 us)

Tue, 26 Oct 2021 14:08:38 CST

How to define the behavior intent and optimizability of these statements.
How to define error reporting behavior of sequential sentence.
Just throw out some reflections on the design of Sequential sentence and Variable.
There are no similar cases in the documentation or TCK.