Must is an object-oriented language in the tradition of Smalltalk-80. It has been designed as a part of the Mushroom project, to investigate new aspects of object-oriented programming. Apart from the sanitisation of a number of Smalltalk-80 features, Must includes major extensions in the areas of multiple inheritance, encapsulation, delegation and sharing of objects between users.
This reports serves as an introduction to Must. A knowledge of Smalltalk-80 is assumed.