While working on the Stars-Nova project at SourceForge.net we wanted to prevent developers from accidentally making commits to Subversion (SVN) without providing a log message. Sometimes developers simply forget to enter a log message, leaving the rest of the team in the dark as to what changes they have made to the repository. You can diff the modified files to try to figure out what they have done, but a short message in the revision log would save you that time. Even experienced developers might on occasion slip and commit with an empty message. Luckily SF.net allows you to correct the log message after the commit has been made (command line: svn propset svn:log "new log message" -r80 --revprop <repository URL>), but that might not be the case for your choice of SVN hosting provider. It might take a while before the developer who forgot to enter the message is made aware of the issue and can correct it so we would rather get the commit right the first time around and save us the trouble.

SVN allows arbitrary server-side scripts to be configured to run on various events (pre-commit, post-commit, etc.). These script hooks offer a lot of flexibility and would have been a good place to centrally enforce a non-empty log message policy. However, because of security reasons SF.net, and all other SVN hosting providers I know of, does not allow user-defined server-side hook scripts. Instead SF.net provides a short list of predefined scripts and a check on log message length is not among the scripts that are included. I have submitted a feature request at SF.net suggesting that they add a server-side hook script such as this and I encourage you to vote for it.

Most of the developers on Stars-Nova use TortoiseSVN and this SVN client just happens to support client-side hook scripts. Based on that I wrote a small script (mmm… JScript) that prevents the user from accidentally executing a commit without providing a message. Currently it does not trim leading and trailing spaces, new lines or other non-printable characters before the character count is checked. However, the minimum character count can be configured so that an accidental space or new line (new lines are composed of two characters: carriage return and line feed) will also stop the commit.

Usage:

1. Make sure you have a recent version of TortoiseSVN (min. v1.5).
2. Open the TortoiseSVN Settings dialog (right-click a folder in Windows Explorer > TortoiseSVN > Settings).
3. Go to “Hook Scripts” and click “Add…”.
4. Choose Hook Type: Pre-Commit Hook
5. Set the Working Copy Path to the directory (or any parent directory) where you checked out your working copy from SVN. “C:\” works as well if you want this script to always execute when you run commit on working copies located anywhere on your C drive.
6. Set Command Line To Execute: WScript <path to script>\MinMessageLength.js
7. Ensure that “Wait for script to finish” is checked.
8. Ensure that “Hide the script while running” is checked.
9. (Optional) Configure the minimum number of characters allowed by changing  the MIN_CHARACTERS variable in the script.

Download the TortoiseSVN client-side hook script

• IEEE 802.15.4 (forms the basis for ZigBee) with integrated antenna
• 3-axis accelerometer (with two range settings: 2G or 6G)
• Temperature sensor
• Light sensor
• Tri-color LEDs
• 6 analog inputs readable by an ADC
• 2 momentary switches
• 5 general purpose I/O pins and 4 high current output pins

SPOT’s main advantage over the BUG is that it has built-in communication. Bug Labs are probably hard at work to build a communication module as well to make it more desirable.

Edit (2008-07-19): Clarified the relation between IEEE 802.15.4 and ZigBee.

The system isn’t completely finished, but soon it will be possible to buy the base module and other modules like:

• BUGlocate – GPS receiver.
• BUGcam2MP – 2 megapixel digital camera.
• BUGview – 2.46″ 320×240 pixels LCD screen.
• BUGmotion – A combined motion detector and accelerometer.

The base module will eventually have built-in WiFi and hopefully they will also make a UMTS (3G) communication module. Applications are developed using Java together with an Eclipse based IDE. I’m very interested to see what kind of applications people might come up with for this thing.

It’s like Lego for grownups.

Some late breaking news about Android: Google Android phones make debut.

Estimated time used for the project the past week: 30 hours

• Topics – used by publish/subscribe (pub/sub) where the communication can be many-to-many.
• Queues – used for point-to-point communication.

In both cases the sender and receiver can be decoupled in terms of both space, time and synchronization as described by Eugster et al. in The Many Faces of Publish/Subscribe. JMS also has a hierarchical topic-based publish/subscribe model which is easy to get into. I’ve been working with Apache MQ to implement a simple JMS based publish/subscribe system. The server part of the system is almost functional, but I haven’t started on the mobile client code yet. I’m not quite satisfied with the way the server system processes all the incoming events because the business logic is spread out into several listener classes. My current goal is to find a more convenient way to arrange the logic so that it will be easier to set different policies for the system. I’ll also start writing some code for Android and find out how easy it is to get Android to talk to a JMS based system. Maybe I’ll have to use one of the alternative transports that Apache MQ provides to make it easier.

I’ve done some checking on IEEE 802.1Q and 802.1p (which is rumored to be defined in 802.1G) in regards to the router that might be used in a practical implementation of this system. 802.1p is essentially a standard for providing QoS at the MAC level. It defines eight different traffic classes which are used by 802.1Q. 802.1Q is the Virtual Bridged Local Area Networks (VLAN) standard. In this standard the IEEE has defined a framework called the Generic Attribute Registration Protocol (GARP) for switches and bridges to work with different types of attribute values. GARP is in turn used by a VLAN management protocol called GARP VLAN Registration Protocol (GVRP) which enables you to manage how VLAN configurations are propagated throughout a network of switches (Cisco has a similar proprietary protocol called VTP).

What seems to be the case is that GVRP can only be used to manage switches when there are several connected in a network. According to this article by HP it looks like the first switch must be manually configured. I’m not entirely sure about the technical details, but from what I can tell it doesn’t seem to align with our needs of just configuring one switch and getting it to forward Internet traffic.

Estimated time used for the project the past week: 40 hours

I’ve checked out Apache MQ and is seems like something I can use. It supports lots of different transport protocols for message exchange and the configuration doesn’t seem to be too tricky. It also supports JMS 1.1 which is the latest version of JMS. I also tested Git a bit and I’ve decided to start using it on this project. At the surface it doesn’t seem to be very much different from Subversion, which I’m used to, but the fact that you can commit to a local repository/index is a big bonus. I look forward to explore the distributed features in Git.

Estimated time used for the project the past week: 38 hours

The original slides were based on the assumption that the mobile phone already knew the status of the alarm system. That isn’t very realistic so the new slides makes use of an event driven system (publish-subscribe) to make the phone aware of the alarm system status. The correct order to read the slides would be to first look at the new slides and then the process continues in the original slides.

I’ve also tried out the Android SDK and written a few small applications to understand how it works. Since there might be better mobile phone frameworks/platforms that can be used I’ve also done some research into other related frameworks/platforms. The disadvantage of Android is obviously that it doesn’t have any supported phones on the market yet, but on the other hand it’s a quite powerful platform compared to some of the others which are already in the hands of consumers.

I estimate that I’ve used about 40 hours on the project the last 7 days. It’s probably a bit more than 100 if you count from when I began and till now. I’ve also put together a project plan which is nice to have.

If you happen to need software for plotting I highly recommend gnuplot. I also tried R for a few hours, but that is a chapter in my life I would rather forget. gnuplot lets me do exactly what I needed in a few simple steps, which is more than I can say about R. It might be because the documentation for gnuplot is so exellent or because there are so many good tutorials, but I managed to whip up a couple of graphs in no time at all. If you want some work done, and you want it done now then gnuplot is your friend.

BTW, this is probably the last DECS progress report as well. At least on this website. At least for now :)

Jan Magne,
Over and out

NOTE: This post has been imported from my old it’s learning ePortfolio DECS blog.

A new draft of the report is complete. This time all the chapters are in place and all the “??” references has been eliminated.

The following is a list of modifications made to chapter 1 and 2:

• Fixed typos and minor word and sentence bugs.
• Moved first paragraph of Section 2.1 to Chapter 1.
• Added reason for redifining ‘one’ to ‘non-zero’ (disambiguation) in second paragraph of Section 2.1.
• Added reduced and identical matrix disambiguation in Section 2.1.
• Fixed notation ambiguity at the end of Section 2.1.
• Added a bit about backtracking in the third paragraph of Section 2.2.
• DeKnuthified some of the content.
• Added formal definition of exact cover to section 2.1. (Does it confuse more than it helps?)
• Added some information and a couple of illustrations about n-queens to the introduction.
• Added n-queens example with primary and secondary columns in Section 2.1.1. It also makes use of the formal exact cover definition.

Pluss the addition of the chapters about implementation, testing and simulation and the conclusion.

NOTE: This post has been imported from my old it’s learning ePortfolio DECS blog.
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