Microsoft Word OpenIssuesInOO. doc

5.3 

Programming language support 

The above discussion may be used to set up requirements for a programming language and 

environment. Overall the environment (and language) should support: 

The exploratory phase. This is the phase where new phenomena/objects are identified. In 

this phase it is necessary to be able  to describe single objects without describing them 

as instances of classes. And it is necessary to be able to describe new objects as clones 

modified from existing objects. Prototype-based languages are clearly superior here. As 

mentioned previously, BETA is one of the few class-based language where it is also 

possible to describe a single object. Many class-based languages also supports cloning 

of objects. However, class-based languages do in general not support implicit 

delegation, but explicit delegation is usually possible. 

 

In this phase it is also necessary to be able to make incremental modification of classes. 

Most class-based languages support some form of incremental modification of classes 

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by means of subclassing with replacement of virtual procedures. Use of multiple 

inheritance  and mixins improve the possibilities for exploratory development. 

 

BETA has less support for incremental modification than most class-based languages, 

since it is impossible in BETA to completely redefine virtual attributes. They can only 

be extended.