Archive for January, 2004

Further thoughts on Distributed Observers

I’ve been reviewing the details of the ActiveTracker implementation of the MVC design pattern. As I noted here, the first problem I ran into was that the observer pattern in ActiveTracker only worked within a single process. I’ve been thinking that I would like a business system that implemented observers in a distributed manner.

However, as I’ve thought about this more, I’ve realized that while the idea might sound good in theory, it can quickly become troublesome.
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Strange ice formation

A couple weeks ago, while walking near the back of the house, I noticed an odd ice formation. It had formed underneath the exhaust pipe from our furnace. I took a few pictures. Here is the best of them.
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This week, I noticed that the ice formation had grown. Here’s one view.
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And here’s a view from the side.
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My wife couldn’t stop laughing for almost five minutes when I pointed this out to her. Sadly, the freezing rain that we have had has deformed the ice, and I don’t think it will ever return to its former shape without some unnatural assistance.


Distributed observers in MVC pattern

Last night, I installed a test project called ActiveTracker. You’ll have to have an account to the MSN group to access the link. ActiveTracker is a modification by Petar Kozul to Rocky’s ProjectTracker. ProjectTracker demonstrates many of the features of the CSLA.NET framework. ActiveTracker includes an implementation of the Observer design pattern.

It was late by the time I successfully built the solution, so I was only able to play around with the general functionality for a few minutes.

One of the Oberver features is implemented in the ProjectList dialog. The dialog lists the projects. If a project is added, the list automatically refreshes and shows the new project. This is a feature that I think can make a system great. Keeping the UI updated with the most current information can be a great benefit. If a user A is reviewing a customer order and user B changes the customer order, the display for user A is automatically updated. I love this concept.

I decided to test the active project list by opening up two instances of the application. I opened the list in the first instance. I added a new project in the second instance. It did not automtically refresh the first instance. I added another project in the first instance, and the display was refreshed, properly showing all the projects.

Every time I have read about the MVC and Observer patterns, the examples have always dealt with “in-process” notifications. I want to cross that boundary! I’ll be looking at the project code over the weekend and try to figure out how it could be modified to register Observers from other processes (and other computers). I think the biggest design decision will be the how to change the communication channel. Isn’t this just like a chat program under the covers?

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Ned Batchelder points out the site He writes:

Judging from the current articles on their home page, they seem to be true to their word, chastising Bush, Gephardt, Dean, the whole bunch. We need all the help we can get in these areas.

I worry when I see sites like this. I think this kind of site turns people off from the political process. When you read article after article about the out-of-context quotes, the misstatements, and the just-plain-false statements made by our poliitical candidates and the lobbying organizations that also participate in the political rhetoric, it’s very easy to get discouraged. This is almost as bad as “negative advertising” that people complain about with every election cycle.

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BMI (Body Mass Index)

Duncan Mackenzie writes that he has made a New Year’s resolution to lose weight. His impetus was his BMI.

Congratulations to Duncan for making this decision. He won’t regret it. Four years ago, my wife and I joined the local YMCA. At the time, I wasn’t obese, but I definitely had some flab around the midsection. My height (5′ 10″) and weight (195) at the time calculated to a BMI (28) that is getting near the obese category.

We did cardiovascular work for a few months and then started lifting weights. Our YMCA has equipment from TechnoGym that keeps track of your workouts. The cardiovascular exercises are done at a measured and constant heart rate, with the machine adjusting the intensity automatically to keep you in your zone.

I dropped down to almost 170 pounds. Then my weight started increasing again, even though I didn’t think that I really looked any fatter. The muscle that I was developing from lifting weights was increasing my weight.

If Duncan sticks with it — and I hope he does — he should forget about the BMI as his fitness improves. The most important factors are how you feel and the energy you have. I would also encourage finding a partner to help you with your motivation. My wife serves as my motivation. There are days when one or the other of us doesn’t really feel like going to the Y, but the other person makes them go. This is a Good Thing.

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Big winter storm?

I’m reading blogs from Seattle that are discussing the big winter storm that they had recently. Some people posted links to photo sites, so I took a look. What did I see here and here? I see maybe two inches of snow on the ground.

I’m sorry, but two inches of snow in Ohio would not constitute a snow day in Akron, Ohio. The salt trucks and the plows would have been sitting on the side of the highway for hours before the snow even started falling.

When I see stories like this, I remember one particular day when I was at the University of Michigan. I played in the basketball band. The night before a Saturday home game, an ice storm passed through Michigan. A literal sheet of ice covered everything. This was the kind of ice storm that breaks off huge tree branches due to the weight of the ice.

I had to walk about a mile from my room to get to the arena. I think I slipped and fell on the ice a half dozen times. By the time the game started, Crisler arena was nearly full. Even with the ice storm, the fans showed up for the game.

It’s all relative, I guess. This may be the most snow Seattle has seen in many years. To me, it’s an occurrence we’ll have several more times this winter.

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If you’re reading this, I’ve successfully used MovablePoster to create a blog entry. Hopefully, this will provide a more efficient way for me to make entries.

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