Today we continue reading Jigsaw : Efficient, low effort mashup isolation by James Mickens and Matthew Finifter. Mashups are web applications that contain code from different principals.
Jigsaw lets mashups be isolated with its framework  and lets them selectively expose private state. We saw some of the features and design goals of Jigsaw. We got familiar with some of the terms such as domain, principal and integrator. We also reviewed box which is an isolation container much like an iFrame for each principal  however there are three differences between a box and an iFrame . Two iFrames can directly access each other's Javascript's namespaces using frame references. But box explicitly prohibits this.  The only way to allow cross principal access is with access modifiers on the principal object. IFrames share same origin.
But boxes enable fault isolation and privilege separation from different principals that originate from the same domain
Another difference is that boxes use nesting relationships to secure the resoutces of the children. With this hierarchy, common object oriented practice of encapsulation and inheritance can be used to better facilitate the management of resources. The third difference between box and iFrame is their use of communication channels.  IFrames uses asynchronous  postmessage calls . These calls can only transmit immutables and not pass objects by reference. Boxes facilitate synchronous calls and don't require marshaling of objects with the use of proxy.
#coding exercise
Find least common multiple of two integers
Int lcm (int x, int y)
{
Return (x*y)/gcd (x,y);
}