Could Sprint Goal & Sprint Backlog be considered as the Boundary of a Sprint?

How important do you think time-boxing is to Scrum Events?

What is a "Boundary" ? What is 

Sprint Goal and Sprint Backlog are with capital because they are designated as specific terms as defined in Scrum Guide(precisely a commitment and an artefact), but I don't see anywhere Boundary ? 

@Laurent VIDAL  this quote is from the Scrum Guide section that describes the Product Backlog. 

The Product Goal describes a future state of the product which can serve as a target for the Scrum Team to plan against. The Product Goal is in the Product Backlog. The rest of the Product Backlog emerges to define “what” will fulfill the Product Goal.

A product is a vehicle to deliver value. It has a clear boundary, known stakeholders, well-defined users or customers. A product could be a service, a physical product, or something more abstract.

The Product Goal is the long-term objective for the Scrum Team. They must fulfill (or abandon) one objective before taking on the next.

That is the only place that the word "boundary" is used in the Scrum Guide. I believe that what @JAYANTO BHATTACHARYA is asking if whether there is an equivalent for the Sprint Backlog since the Guide does not state one. 

While I'm here..... +1 for @Ian Mitchell's comment.