Monthly Archives: May 2006

Sound Engineering and Premature Extrapolation

In a recent post Patrick Logan has a few pointers and quotes about Premature Extrapolation. Henry Petroski’s Design Paradigms: Case Histories of Error and Judgment in Engineering provides a similar perspective, albeit from an angle that has nothing to do with computers.

One of the key messages that Petroski’s book is trying to get across revolves around what Patrick calls premature extrapolations. Paraphrasing Petroski, mediocre engineers scale up designs that worked in the past, hoping that they will also work at a larger scale. Good engineers don’t blindly scale; they start from the other end, analyzing potential failures and then designing to prevent them. One of the many examples he uses to illustrate this point is John A. Roebling’s Brooklyn Bridge (which belongs in the latter category) and Clark Eldridge’s Tacoma Narrows Bridge (which belongs in the former). The book offers many other examples.

I’ve been a fan of Alan Kay’s “Good ideas do not always scale” for many years. I’ve even used it in Chapter 18 of PLoPD4. After reading Petroski’s book I thought that any computer scientist going through it ought to be able to come up with that line.

Silicon Valley’s Secret Sauce

In his latest essay Paul Graham dissects what makes Silicon Valley “the” Silicon Valley. As someone who lived and worked in two (self proclaimed) Silicon Valley-like technology parks (the Silicon Alps and the Silicon Prairie) I found Graham’s discussion of the key ingredients interesting. (BTW, Wired sheds additional light over the Silicon envy.) While Grenoble has great schools and location (with ski slopes a 45 minute bus ride from the campus), and Chambana great schools and cornfields (with tall, thick corn next to the movie theater’s parking lot), neither achieved the Silicon Valley critical mass while I lived there.I also have the benefit of having read an excellent book on the topic, and am waiting for a second one to be published:

  • The Man Behind the Microchip: Robert Noyce and the Invention of Silicon Valley, a great book in at least 3 ways: the story of Robert Noyce; the history of semiconductors (from Ge transistors to Intel’s 4004); history of the Valley.

  • Broken Genius : The Rise and Fall of William Shockley, Creator of the Electronic Age is not out yet, but I’ve added it to my wishlist after hearing an NPR interview with the author.

Pattern Languages of Program Design

After a long gestation the fifth volume of Pattern Languages of Program Design (PLoPD) has been published.

Myself, Markus and James selected among patterns workshopped at PLoP conferences from 1998 through 2004. We structured the book in six parts. Part I focuses on design and contains patterns aimed at people designing object systems. As the Internet and embedded systems continue to expand their reach they bring with them concurrency and resource management problems; Part II contains patterns on these topics. Part III continues the shift from one to many applications and contains patterns for distributed systems. The domain specific patterns from Part IV focus on mobile telephony and Web-based applications. Part V shifts gears to architecture and comprises patterns that tackle composition, extensibility, and reuse. Finally, Part VI offers a smorgasbord of meta-patterns for improving the quality of pattern papers and helping their authors.

Here’s what you can find in each chapter:

  1. The Dynamic Object Model pattern combines ideas from class-based (like Java) and prototype-based (like Self) languages to address dealing with elaborate flexibility requirements.
  2. The Domain Object Manager allows application code to handle transient and persistent domain objects while supporting multiple data stores or application servers, keeping the domain objects independent of the persistence or middleware APIs.
  3. Encapsulate Context provides value to developers who are seeking ways to lower the ripple effects of code changes regardless of programming language, allowing them to manage an increasing number of call parameters without introducing global variables.
  4. A Pattern Language for Efficient, Predictable, Scalable, and Flexible Dispatching Components addresses the challenges associated with developing dispatching components, providing one of the building blocks of a handbook for distributed real-time and embedded middleware.
  5. Triple-T focuses on writing software for real-time processing is hard and poses unique challenges, covering five patterns harvested from time-triggered bus architectures for safety-critical real-time systems, such as the ones employed by Airbus airplanes or BMW and DaimlerChrysler automobiles.
  6. Real Time and Resource Overload Language presents a pattern language for designing reactive systems that gracefully accommodate load bursts, applicable to any systems that process incoming requests, such as web servers, middleware, OLTP, and so on.
  7. Drawing upon examples from several systems that deal with distribution De-Centralized Locking covers a pattern for managing locks in the context of distributed systems.
  8. The Comparand Pattern focuses on dealing with identity when working with objects from different hosts or processes within a distributed system.
  9. Service Discovery tackles a common problem in practical ways, distilling solutions from well-established examples such as SLP, JXTA, UPnP, LDAP, DNS, and the now ubiquitous and IEEE 802.11.
  10. MoRaR is a pattern language focused on mobility and radio resource management.
  11. Content Conversion and Generation on the Web is a pattern language aimed at people building applications that deal with dynamic HTML generation.
  12. Plug-ins represent a popular technique for extending applications, allowing users to late-bind new functionality. The Patterns for Plug-Ins pattern language covers techniques mined from a wide body of software, including operating systems, web browsers, graphics programs, and development environments.
  13. The Grid Middleware Architectural Pattern covers the architectural elements of grid middleware as well as guidelines for implementing and deploying them.
  14. Targeting application developers integrating components written in different languages or built with hetereogenous component concepts, the Patterns of Component and Language Integration distill insight from systems that include Apache Axis and the Simplified Wrapper Interface Generator (SWIG).
  15. Patterns for Successful Framework Development
    covers a set of patterns for mitigating the mismatch between the recommended practice of building frameworks and the reality of many software development projects.
  16. Distilling from 10 years of writing and reviewing patterns Advanced Pattern Writing provides advice for improving pattern writing.
  17. A Language Designer’s Pattern Language explains how does one generate a pattern language from a system of forces.
  18. The Language of Shepherding focuses on analyzing and providing feedback about patterns.
  19. Patterns of the Prairie Houses uses the design themes of Frank Lloyd Wright’s prairie houses as an exploratory vehicle for showing how people should approach pattern mining and writing.