Dr. Dobb's Journal - November 2007 - (Page 53)

d11jiri_p8db 9/13/07 1:59 PM Page 53 inheritance. In Figure 2, classes Connector, Geometry, Wire, and Contact form a pattern Composite that allows complex hierarchical designs from several different types. This pattern is different from the commonly used association called “composition aggregate,” which is simply a specific implementation of OneToMany. An example of a composition aggregate is the relation between Master and Block. Each block belongs to only one master and ceases to exist if its master is destroyed. • Pointer diagrams representing C data structures were eliminated by the introduction of class libraries. Software complexity is a serious problem and the prevalent use of graphical tools including UML fits this observation. If this popularity cycle really exists, it implies that the arrival of a new programming technique is imminent and a new paradigm will eliminate or reduce the use of UML class diagrams. The new paradigm would have to include the major improvements that UML gave us: • Instead of programming with collections, UML uses more general associations. • Associations and classes are both treated as first-class entities. Popularity Cycle of Graphical Tools We have observed an interesting cycle. Programmers write programs that grow bigger and more complex until their own authors cannot debug or modify them safely. Graphical tools become popular to manage the complexity, but then a new programming language or new programming paradigm is invented, programmers return to the more compact textual programming, and a new cycle begins. In “The Inevitable Cycle: Graphical Tools and Programming Paradigms” (IEEE Computer, August 2007; www.codefarms .com/OOPSLA07/workshop/cycles.doc), we describe three historical cycles: • Flow charts were used to manage spaghetti logic in the code but were eliminated by structured programming. • Diagrams of table indices helped to manage Fortran programs but were eliminated by the introduction of C structures and pointers. Listing One class ChipLib { Collection masters; Master *chip; Collection geometries; }; class Master { String name; int xWidth,yWidth; Collection blocks; Collection nets; }; class Block { String name; int x,y; int orientation; Master *master; Collection termsByBlock; }; class Net { String name; Collection connectors; Collection termsByNet; Collection pins; Master *master; }; class Terminal { Block *block; Net *net; Net *masterNet; }; and so on Increased client demand for modeling forecasting optimization and data mining functionality BUY OR BUILD ? * To help you decide, download the “Buy or Build” worksheet from Numerical Algorithms Group at: www.nag.com/buyorbuild *and debug, then cross your ÀQJHUVWKHQ rebuild, then weep and . . . RES ULTS MAT TER. TRUST NA G . in your products has you asking: should I . . . Figure 2: UML class diagram of the data supporting the hierarchical VLSI chip design. Compare with Listing One where each association is implemented in a different color with the exception of green (blocks and master here). November 2007 l www.ddj.com l Dr. Dobb’s Journal 53 http://www.codefarms.com/OOPSLA07/workshop/cycles.doc http://www.codefarms.com/OOPSLA07/workshop/cycles.doc http://www.nag.com/buyorbuild http://www.nag.com/buyorbuild http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - November 2007

Contents Hmmmm Alia Vox Developer Diaries Developer’s Notebook Smart Compilers - But Smart Enough? Conversations Grid-Enabling Resource-Intensive Applications Distributed Computing: Windows and Linux Adobe AIR: Desktop/Web Convergence Transparency on Demand Reusable Associations Effective Concurrency The Agile Edge Swaine’s Flames

Dr. Dobb's Journal - November 2007

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