Hi I run into these different types of reprsenting an object in uml diagrams and was wondering which is the correct one or the most used one?
The following pictures are examples of collaboration diagrams one on which the objects are circles (interfaces, controllers, ...) and the other squares?!
PS: it's not just collaboration diagrams but others types too.
The standard notation symbol for objects is a rectangle.
Yet UML is highly adjustable and main methods for that are stereotypes and profiles. Stereotypes can have icons to be used as a replacement for a standard UML notation symbols.
The circles based icons in the first picture are standard, widely recognized and accepted icons to represent stereotypes for ECB design pattern classes (Entity, Control, Boundary). Add the UML inherent actor's sticky figure notation and you have all the pieces.