GolamMostafa:
In a beginner/teaching environment, portability is desirable.
(1) The sentence has two parts: an introductory phrase and the independent clause.
IMHO it does not have two parts and, in particular, the second part is not independent.
Structurally it is the same as "in school diligence is desirable"
And, as I said in Reply #23 the sentence is awkwardly conceived in the first place.
IMHO an example of a sentence with an independent clause would be
"In school diligence is desirable, some students do not realise that"
Grammar MUST be subservient to meaning and content - in other words, first figure out the simplest and clearest way to say what you want.
...R