http://www.handbookofsoftwarearchitecture.com The Handbook catalogs the software architecture of a large collection of software-intensive systems. en-us Copyright (C) 2000-2008 by Grady Booch http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#606 http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#606 here.

Quote of the day:

The way of the world is meeting people through other people.
Robert Kerrigan

]]> 28 Jul 2010 01:58:36 MST http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#605 http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#605 Computer History Museum, located in Mountain View, California, is not only a museum of hardware but also a museum of software. As reported by Arik Hesseldahl of Bloomberg today, with the permission of Apple Computer, the Museum has made available the original source code of MacPaint as well as the underlying QuickDraw graphics library.

MacPaint was written by Bill Atkinson, a member of the original Macintosh development team. Originally called MacSketch, he based it on his earlier LisaSketch (also called SketchPad) for the Apple Lisa computer. Bill started work on the Macintosh version in early 1983. He also created QuickDraw (then called LisaGraf) for the Lisa. Andy Herzfeld, another key member of the team, considers QuickDraw "the single most significant component of the original Macintosh technology" in its ability to "push pixels around in the frame buffer at blinding speeds to create the celebrated user interface."

MacPaint was released with the Macintosh in January, 1984. The application was written in Apple Pascal and was packaged in a single file of only 5,822 SLOC, together with an additional 3,583 lines of assembly code for the underlying Motorola 68k microprocessor, used to implement routines needing high performance as well as certain interfaces to the operating system. QuickDraw was the Macintosh library for creating bit-mapped graphics and was used by MacPaint and other applications, and consisted of a total of 17,11 lines of 68 assembly code packaged in 36 files.

Quote of the day:

Design is not just what it looks like and feels like. Design is how it works.
Steve Jobs

]]> 20 Jul 2010 00:24:21 MST http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#604 http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#604 Patterns-Based Engineering: Successfully Delivering Solutions via Patterns. I had the opportunity to read their manuscript while in progress, and very much enjoyed what they had to say and how they said it.

You can follow more of their work here.

Quote of the day:

Research is just like sex. Sometimes something useful comes from it, but that is not why we do it.
Richard Feynman

]]> 15 Jul 2010 13:17:07 MST http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#603 http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#603 Plato. Given that I was at the Air Force Academy, AirFlight was a favorite, but I also remember flirting in chat rooms (Talkomatic) and using instant messaging (Term-Talk). And that was thirty-plus years ago.

The Computer History Museum recently held a retrospective on Plato and the videos of that entire conference are now available here. While you are there, do check out the rest of the videos on the Computer History Museum YouTube channel. There are currently a legion of artifacts, with everything from historic computer films from the 1950 and 1960 decades, to museum lectures and panels, exhibit films, and co-production pieces.

Quote of the day:

I arise in the morning torn between a desire to save the world and to savor the world. That makes it hard to plan the day.
E. B. White

]]> 24 Jun 2010 10:35:13 MST http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#602 http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#602 Rinse the Algorithm.

Quote of the day:

As complexity starts becoming more and more important, architecture is always going to dominate material.
Alan Kay

]]> 20 May 2010 00:35:18 MST http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#601 http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#601 Barbie Millicent Roberts, the best-selling doll of all time, has launched her latest career as a computer engineer.

Quote of the day:

I want one.
Tony Stark

]]> 17 May 2010 01:47:22 MST http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#600 http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#600
Actually, this kind of resonance is not uncommon with complex systems. Hit a series of waves in just the right way and you'll break the back of even the most carefully engineered ship; encounter a particular combination of winds and you'll topple the tallest building. You can design for and test against most such conditions, but the state space of any complex system is such that you can't afford to design and test against all possible conditions. So, common practice is to over engineer the system, be certain that you operate it within its intended design envelope, and when things that you could not design or test for happen, patch the system so that it won't happen again. Hopefully, no one dies in the process.

Now, I'm not a financial expert, but my take is that last week's stock market jitters were a manifestation of this kind of complex system resonance. The new SEC rules that have been put into place are thus a (reasonable) systemic patch, for they attempt to break the dynamic coupling among computer trading on different exchanges, a coupling that could not have been anticipated nor tested for. I say "could not have been anticipated" because you can't a priori predict where and when these kinds of resonances will take place; "nor tested" because the highest fidelity simulation of the market is the market itself, and any lesser simulation would likely never exhibit such behavior at all. At worst, a systemic resonance such as this will tear a system apart. Having a human in the loop or having explicit governors vastly changes the dynamics because, from a control systems perspective, you have a very different frequency dynamic going on, one that will either dampen or neutralize the resonance.

What's the lesson here? Software-intensive system are not immune to such systemic problems. Indeed, as we build more systems of systems, it's increasingly likely that we will see more of these kinds of strange, intermittent behaviors. Problem is, each individual system may be operating perfectly, but it's the combination of such systems under particular operating conditions that produces resonance. When that resonance happens, there will be much finger pointing, but that won't solve anything, because it is a systemic problem. Furthermore, we really lack the analytic tools to test for much less reason about such problems in software-intensive systems. So, the lessons from systems engineering apply to software-intensive systems as well: over engineer them, operate them within particular design envelopes; patch the system when it resonates. I should add that having loosely couples systems helps a great deal too, because you give the system room to move, so to speak.

Quote of the day:

It turns out that an eerie type of chaos can lurk just behind a facade of order---and yet, deep inside the chaos lurks an even eerier type of order.
Douglas Hofstadter

]]> 10 May 2010 16:07:21 MST http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#599 http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#599 Many Bills, a Web-based mechanism for exploring congressional legislation.

Quote of the day:

All the legislation in the world will not abolish kissing.
Elinor Glyn

]]> 19 Apr 2010 11:51:44 MST http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#598 http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#598 video about the rise and fall of the waterfall process.

I had the pleasure of working with Win Royce some years ago (and I have the pleasure of working with his son, Walker). Pay close attention to the scene around 4:15, in which it is made clear what Win was really trying to say (but which was oft ignored).
Quote of the day:

If debugging is the process of removing bugs, then programming must be the process of putting them in.
Anoymous

]]> 07 Apr 2010 22:51:48 MST http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#597 http://www.handbookofsoftwarearchitecture.com/index.jsp?page=Blog#597
Quote of the day:

The Internet is the world's largest library. It's just that all the books are on the floor.
John Allen Paulos

The Internet is just a world passing around notes in a classroom.
John Stewart

The Internet isn't free. It just has an economy that makes no sense to capitalism.
Brad Shapcott

A journey of a thousand sites begins with a single click.
Anonymous

]]> 19 Mar 2010 11:49:17 MST