I am implementing a machine translation system.
Are questions about how they implement something on topic?
I was about to ask how phrase-based SMT splits an input up into phrases. Then I figured I'd ask here first to see if it's in scope or not.
It depends on the focus of your question.
If your concern is primarily about how to exploit linguistic heuristics to solve the task, about the basic functionality of common algorithms applied in the modeling or processing of natural language (such as parsing techniques), what research has been done about a specific NLP problem or what computational linguistic resources/tools are recommendable for performing a certain task, then it's on-topic here.
If, by implementation, you mean to ask about the details of programming, i.e. specifics about the code you're writing, then it's better to ask it on Stackoverflow.
Rule of thumb:
If your question can be asked and answered without including actual code, it's probably concept-focussed enough to fit on a linguistics site.
If asking your question using solely natural language running text won't really help solving your problem, you're probably better off at Stackoverflow.
As far as your current question is concerned, since it seems to be more about general strategies in a natural language processing problem and not about specifics of program code, I'd say it's on-topic here.