Advertisement

Concluding thoughts: Object-orientation and mobile agents
Object-oriented programming represented a higher level of abstraction than procedural programming. Early proponents of object-oriented programming promised that this higher level of abstraction would make programmers more productive, code easier to understand and maintain, and make possible better development tools. Although opinions may vary as to the extent to which these promises have been fulfilled, for the most part, the software development community has embraced the object-oriented approach.

Mobile agents may simply represent another step in the evolution of the object-oriented paradigm. Aglets are Java objects that can autonomously move from host to host. Like a traditional object, an aglet has state, behavior, and identity. Unlike a traditional object, however, an aglet also has location.

Next month
Next month will be the final article in my long series that covers Java bytecodes. It will discuss the various ways the Java virtual machine invokes methods.

Resources

• The aglets home page is here:
  http://www.trl.ibm.co.jp/aglets
• IBM's Massively Distributed Systems research page has several interesting agent-related links:
  http://www.research.ibm.com/massdist
• Servlets are code that can be sent in the reverse direction from applets, from a client to a server. This model enables a client to execute a script on a server without requiring that the script already be present at the server. There are many servlet-related links at the bottom of Phil Chang's servlets article from last month's JavaWorld:
  http://www.javaworld.com/javaworld/jw-04-1997/jw-04-servlet.html
• The IBM research paper titled "Mobile Agents: Are they a good idea?" by Harrison, Chess, and Kershenbaum is available for download in PostScript format here:
  http://www.research.ibm.com/massdist/mobag.ps
• For aglet code samples and another perspective on Java aglets, check out this article by Bret Sommers, in last month's JavaWorld, "Agents: Not just for Bond anymore":
  http://www.javaworld.com/javaworld/jw-04-1997/jw-04-agents.html

About the author
Bill Venners has been writing software professionally for 12 years. Based in Silicon Valley, he provides software consulting and training services under the name Artima Software Company. Over the years he has developed software for the consumer electronics, education, semiconductor, and life insurance industries. He has programmed in many languages on many platforms: assembly language on various microprocessors, C on Unix, C++ on Windows, Java on the Web. He is author of the book: Inside the Java Virtual Machine, published by McGraw-Hill. You can reach him at bv@artima.com.

This article was first published under the name Under the Hood: Solve real problems with aglets, a type of mobile agent in JavaWorld, a division of Web Publishing, Inc., May 1997.