Q:

What's the difference between a centralized and a distributed sequence diagram?

I'm new to UML and I have crossed path with sequence diagram, and realized that there's 2 types: distributed and centralized. Can anyone explain me the differences?

A:

centralized control, with one participant doing most of the processing and the other participants there to supply data. 
Example:

Distributed control, in which the processing is split among many participants, each one doing a little bit of the algorithm
Example:

Both styles have their strengths and weaknesses. Most people, particularly those new to objects, are more used to centralized control. In many ways, it’s simpler, as all the processing is in one place; with distributed control, in contrast, you have the sensation of chasing around the objects, trying to find the program. 
Despite this, object bigots like strongly prefer distributed control. One of the main goals of good design is to localize the effects of change. Data and behavior that accesses that data often change together. So putting the data and the behavior that uses it together in one place is the first rule of object-oriented design. 
Furthermore, by distributing control, you create more opportunities for using polymorphism rather than using conditional logic. If the algorithms for product pricing are different for different types of product, the distributed control mechanism allows us to use subclasses of product to handle these variations.

