1. Towards Multi-Paradigm Software Development Valentino Vranić vranic@elf.stuba.sk Department of Computer Science and Engineering Faculty of Electrical Engineering and Information Technology Slovak University of Technology in Bratislava

2. 1 Overview Several new approaches to software development have a multi-paradigm character Some are explicit with this (e.g. multi-paradigm design for C++) And some are implicit (e.g. aspect-oriented programming) The main points of this presentation:  Use of the term paradigm regarding software development  Multi-paradigm approaches to software development

3. 2 The Meaning of Paradigm Introduced in science by Thomas Kuhn: –a consistent collection of methods and techniques accepted by the relevant scientific community as a prevailing methodology of the specific field Widely used (and abused) in computer science Used at two levels: –large-scale paradigms –small-scale paradigms Multi-paradigm –the application of multiple paradigms Metaparadigm –a paradigm of paradigms: shows how to select and combine paradigms

4. 3 Large-Scale Paradigms The essence of the software development process Refer to all the phases of the software development A change of paradigm: evolution or revolution A change of a paradigm in science is taking part through the scientific revolution A paradigm is dominant in its field, i.e. there can be only one

5. 4 Large-Scale Paradigms (contd.) But there are several software development paradigms currently existing (imperative, procedural, object-oriented, functional, logic…) Some paradigms seem to evolve: Imperative programming Procedural programming Object-oriented programming

6. 5 Small-Scale Paradigms The other use of the term paradigm: to denote programming language mechanisms Scope, commonality and variability (SCV) analysis Example: procedures –S: a collection of similar code fragments –C: the code common to all fragments in S –V: the “uncommon” code in S; variabilities handled by the procedure parameters and/or the code before or after the procedure call Some other small-scale paradigms: templates, objects, inheritance… Large-scale paradigms consist of the small- scale paradigms

7. 6 Aspect-Oriented Programming Aims at modularization of the crosscutting concerns (resulting in the tangled code) Main AOP approaches (next slide) build upon the OOP AOP is not OOP bound — it is also applicable to procedural or functional programming Another paradigm is needed to which AOP is to be applied

8. 7 Generative Programming Composition Filters Demeter/Adaptive Programming Subject-Oriented Programming Generic Programming Domain-Specific Languages Aspect-Oriented Programming Generative Programming Aims at automatic software manufacture Has to be tailored to a particular domain yielding a paradigm  GP is a metaparadigm Xerox PARC Aspect-Oriented Programming Object-Oriented Programming

9. 8 Multi-Paradigm Programming in Leda Leda was created as a multi-paradigm language — in terms of the large-scale paradigms Enables combination of the procedural, object- oriented, functional and logic programming Problems: –extension to other paradigms –no support in selecting and combining paradigms

10. 9 Multi-Paradigm Design for C++ Intended for C++, but can be tailored to any richly expressive language Makes an explicit use of the small-scale paradigm concept Two analyses, commonality and variability, performed both on application and solution domain Lining up yields which paradigm is to be used for which feature

11. 10 Intentional Programming Programming abstractions are limited by the fixed syntax programming languages IP: a program represented by the AST (called intentional tree) Requires special programming environment Binary format for the program files MPD would contribute to more regularized use of the IP IP enables creation of the new intentions — small-scale paradigms

12. 11 Conclusions The need to distinguish between large- and small-scale paradigms Multi-paradigm software development is a growing concept Widely present at implementation level Has to be “legalized” at design level MPD — a possible basis for future multi- paradigm software development MPD requires further improvement: –extended notation –method incorporating traditional approaches into MPD –the connection with design patterns