Bugs in the Wild: The Paradoxical Error Message Edition

A friend recently sent out a screenshot of a quite humourous error message. He was attempting to free up some space on a network drive, by deleting some files, when he received this less than helpful error message:

Error message that appeared when deleting a file

The text in the error message is:

Cannot delete week4: There is not enough free disk space.
Delete one or more files to free disk space, and then try again.

It can be seen that this is a faulty error message, and something else is really afoot; one cannot delete files if one cannot delete files.

An interesting question here is why this error message came up? Is this the actual reason the file cannot be deleted, if so a different error message should be displayed so as not to confuse people. If this is not the cause of the issue, then why did this message get displayed?

–Steve

Bugs In the Wild: WYSIWYG in WordPress Edition

I ran into this issue when creating my post for importing/exporting individual tables in MySQL. The issue resolves around the principal of WYSIWYG (What you see is what you get).

For one of the MySQL commands it was necessary to have two dashes (or minuses) next to each other, as can be seen in my the post mentioned above.  In the WordPress text editor displayed the two dashes properly in both the visual and HTML views, but after I had published the post, the two dashes where displayed (and when copied acted) as a single dash! For example the character in the quotation is seen as two dashes in the editor “–” but as can be clearly seen it is displayed as a single dash.

I tried for a while to resolve the issue, but I ended up just spacing out the dashes, like so “- -”, so that it could be seen that there were actually two dashes.

I feel this falls under a WYSIWYG type issue as in the text editor I was able to see the two dashes properly, but then when the post was published the same thing was not displayed therefore what I was seeing n the editor was not what I got in the post.

–Steve

Exporting and Importing An Individual MySQL Table

In moving databases from development to production it is sometimes necessary to export individual tables so that they can be imported into another database.

Exporting the Table
To export the table run the following command from the command line:
“mysqldump -p - -user=username dbname tableName > tableName.sql”

This will export the tableName to the file tableName.sql.
[NOTE: there should be no space between the two dashes, but I have to write it that way so that it display properly].

Importing the Table
To import the table run the following command from the command line:
mysql -u username -p -D dbname < tableName.sql

The path to the tableName.sql needs to be prepended with the absolute path to that file. At this point the table will be imported into the DB and you are ready to go!

I ran into this issue when attempting to add new tables to my database. I am unable to run the “LOAD DATA INFILE” command, that I had previously used to populate tables, because Webfaction does not give the permission to run the command. Therefore the simplest solution was to export a table from the MySQL database on my personal machine and then import it to the database on the Webfaction server, using the export/import commands seen above.

Hope this helps someone out with exporting individual tables and as always if any clarification is needed or I missed something feel free to let me know.

–Steve

Anatomy of an Error Message – A Windows Vista Example

I have recently had a somewhat frequent recurrence of an error message on my laptop, which is running Windows Vista. The error message can be seen below:

Windows Vista Error Message

The error message popped up (for seemingly no apparent reason), and to make matters worse, when I clicked cancel a new instance of the error message popped up, and I had to close it about 30-40 times before it stopped popping up!

You’ll notice that the first issue with this error message is that it is extremely uninformative and has indecipherable information, something the user should never see. This lack of information made so that I was unable to identify what was causing the error therefore I was not able to stop it from happening (as a quick note, I did not unplug any disks at the time, so it did not have to do with that). Subsequently, since the first incident, this has occurred a few more times with no real pattern as to what is causing it.

A bad error message is good illustrator to what a good error message should be. A good error message should have the following:

• An informative title – A user should know what caused the issue
• Actual error message should provide user with information on how to fix the problem
• Finally it should provide the user with actions that will help fix the problem identify in the message

The only thing the above error message has going for it is that its title gives a clue as to the issue.

To quickly summarize, the goal of an error message is to inform the user that there has been an error, what caused the error, how to fix the error and finally some actions you can take to fix it.

Two Forms One Page: Explanation of the HTML Form Action

When I started my web application for my design project I knew absolutely nothing about django, html, css… so basically any and all web technologies. Therefore for a very long time I did not really know the purpose of the action in the form declaration ( <form action=’.'>) or what the ‘.’ actually meant.

It is actually very simple, the ‘ action=”.” ‘ denotes where the form is being submitted (what URL is being called). Specifically, the “.” means that that form will be submitted to the current location (same page), for example if your url was http://mysite.com/search the form would be submitted to http://mysite.com/search.

Now that we know what the action does, it can be used to have two forms on the same page submit to different location. I created a page where a user can either login or register. To have the two forms submit properly I have the following actions for the two forms:

Login Form: <form action=’/accounts/login/’>

Registration Form: <form action=’/register/’>

Now when the login form gets submitted the /accounts/login/ is called and when the registration form gets submitted the data is sent to /register/. An important note is that the action gets performed on the specified location BEFORE the last ‘/’. For example if I had , the action would be performed on the home page and not the register page. Therefore it is important to always have the trailing ‘/’ .

Hopefully this saved someone some trouble getting multiple forms setup.

If you need any clarification, or more details, drop me a line and I’d be more than happy to help.

–Steve

Django – Going from development to production

I recently took my 4th year Systems Design Engineering project, which is a Django web application, from the development environment into a production environment and had quite a bit of difficulty, that could have been easily avoided if I had a tutorial to follow!

1. Hosting & Domain:
   The first thing is to either build a web host or purchase hosting from a company. I purchased hosting form Webfaction as they had a one click deployment for a Django application.  A domain name should also be purchased, I bought mine from GoDaddy for 10$.
2. Getting Setup on Webfaction:
   Webfaction takes a little while to setup your account~2-3 hours, when it is complete you will receive an e-mail and you can then login to their control panel. There are some resources that Webfaction offer to help you get setup, the first is a screencast and the other is a text guide.
3. Setting up the Database
   Once you are in the control panel area there are a few things you’ll want to do. Firstly you will need to add a database (if you have not done so), this can be done by clicking add new databse from the ‘Databases’ drop down menu.
4. Adding your domain name
   Under domains/websites select the domain link. Click on the add new button, and then enter your domain, for this tutorial we will assume it is ‘mysite.com’. When you add the domain be sure to enter in the subdomains field ‘www’ .
5. Setting up the application to serve the static media
   The next thing you will want to do is to add Static/CGI/PHP application to your website to serve the static media files (this is highly recommended). To do so go to the applications link under the domains/websites tab. Next click the add new button, name the application ‘media’ and select the app type as ‘Static/CGI/PHP’ and finally click the create button. Now you have to add the application to your domain, to do so click on the ‘websites’ link, and click the edit button for your website. Under subdomains select any that you would like to include, and then under site-apps ensure that you select the media app and set the url/path to ‘/media’. Click update, and you should be taken to the page as seen here:
   

   After site applications have been configured

6. Changes to your settings.py file:
   There are a few changes that need to be made to the settings.py file:
   DEBUG = False MEDIA_ROOT = ‘/home/username/webapps/media/
   MEDIA_URL= ‘/media/’

   Replace ‘username’ with the username that you selected for your webfaction account, now you are ready to upload your site. You will also need to change your database settings such that they match the new database created by webfaction.

7. Uploading your web applicaion
   To upload your web application, you will need to upload your ‘mysite’ application to the webfaction server. To do so you will need to download putty (an ssh tool) so that you can ssh into the host, the connection info as well as the username and password are provided by webfaction. Once you are logged in navigate to ‘/home/username/webapps/django/’ and replace the ‘myproject’ folder with your web application folder that you used for development. Once it has been uploaded you will need to tell apache where to locate the project, so naviagte to ‘/home/username/webapps/django/apache2/conf/’  and edit the httpd.conf file. You will need to change th PythonPath and SetEnvPythonPath “['/home/username/webapps/django', '/home/username/webapps/django/lib/python2.5'] + sys.path”
   SetEnv DJANGO_SETTINGS_MODULE  sitename.settings

   To setup your static media you will need to and another few lines of code to the same httpd.conf file:

   <Location “/media”>
   SetHandler None
   </Location>

   Save the file, and thats all you need to do in the apache folder. One last thing you will need to do is put your existing media into the media directory so that your static files are properly served by apache:
   /home/username/webapps/media

8. Setting up the Database :
   The first thing you will need to do is to get a dump of your current sql database, I personally used mysql, and got a dump with the following line of code:   mysqldump -u [username] -p [password] [databasename] > [backupfile.sql] . Now you need to navigate to your project on the webfaction host, /home/username/webapps/django/mysite/ and enter the db shell by entering: python2.5 manage.py dbshell . You should see a mysql command line promp where you can upload your mysql dump: mysql – u user_name -p your_password database_name < file_name.sql. Now  you have your database loaded up and you are ready to go.
9. Firing it Up:
   Everything is ready to go, the last step is to fire up your apache server, to so navigate to /home/username/webapps/django/apache2/ and enter the command bin/stop to stop it in case it was running, and then enter bin/start to start it up.
10. Pointing the domain name to the webfaction name servers:
    There actualy is one last thing to do, and that is on the domain side of things. You will have to go to the site where you purchased your domain name, and then change the nameservers to those at webfaction, which are as follows:
    ns1.webfaction.com
    ns2.webfaction.com
    ns3.webfaction.com
    ns4.webfaction.com
    Now you can navigate to http://mysite.com and it should come up, congrats your site is live!

There you have it, from development to production. Also remember if you make any changes to the settings.py file you will have to stop and then restart the apache server.  Hopefully this quick tutorial will help you get up and going, and if you have any other questions feel free to ask me!

–Steve

Revolutionary vs. Evolutionary Design – The 3rd Generation iPod Shuffle

I am sure many of you have seen the new 3rd generation iPod shuffle, as seen here. What really caught my attention was this line from the VP of product marketing:

“The new iPod shuffle is the world’s smallest music player and takes a revolutionary approach to how you listen to your music by talking to you, also making it the first iPod shuffle with playlists.”

What catches my attention is that they state that their new ‘revolutionary’ VoiceOver feature;  the ‘revolutionary’ VoiceOver feature will tell you the song titles, artists and playlist names. To me the fact that the shuffle talks to you is not a revolutionary change in the way people listen to music.I think they need a little lesson in what constitutes a revolutionary design and what really is an evolutionary design.

The terms evolutionary and revolutionary may seem very similar but there is an important difference, I’ll start by describing both. Evolutionary designs are ones that simply take a design to the next logical step, for example the first iPod nano with video support was an evolutionary design, it brought video to a small portable device but it did not really change how people watch videos. Revolutionary designs are those that fundamentally change how something is done, a classic example of a revolutionary design is the printing press, it fundamentally changed how information was desiminated and possibly led to the prevalence of literacy.

It should be obvious at this point how the new VoiceOver technology is not a revolutionary step in the way that we listen to music. The VoiceOver technology simply provides the same information that a visual display would, just through the auditory channel, thus not really changing how we listen to music.

To me, an example of a revolutionary design for a new music player would be one that could sense our moods and then auto create playlists based on them, or one whose controls could be operated based on our thoughts instead of the current tactile interface. Now obviously I know that these ideas are a little far fetched and currently infeasible, but one can always dream!

———————

Do you agree or disagree with the arguments made above? Let me know, I’d love to hear your thoughts.

An upgrade to the mechanical pencil

As a foreword, I am aware that this is one of those ‘out there’ ideas that may never be feasible, but despite that I feel it is a good idea!

The idea came when I was studying for my image processing midterm. I was making notes with my trusty mechanical pencil when I realized that every 3-4 words the lead in the pencil would become dull, I am using 0.5mm lead, in case it matters. When the lead becomes dull my writing becomes very unclear, so I would spin the pencil around about 180 degrees to where the lead was now sharp, and then another 3-4 words I would again spin the pencil to get to the sharp part of the lead. After doing this for a while, I thought to myself, why should I have to spin this pencil 20 times a minute! This is when the idea struck.

I propose that new mechanical pencil designs have a system that results in the lead rotating on its own so that the lead is always sharp. There are a few implementations here, the pencil could have a mechanism where the lead is always turning slightly, the actual amount would have to be ascertained through some calculation in how quickly lead dulls. Another implementation would be for the lead to ‘know’ when to rotate; if the pencil was smart enough it could know how long a person had been writing and the pressure with which they were writing. With this information it would be possible to know when the lead would become dull, therefore at the point of dullness the lead would automatically rotate. A final implementation idea, and probably the most feasible, is to place another button on the side of the pencil that would rotate the lead 180 degrees for you.

The drawback is obviously that it would cost more money to implement this kind of system, and mechanical pencils are meant to be inexpensive. That being said, if there were an automated lead rotating mechanical pencil that did happen to be more expensive, I would definitely be the first to rush out and get one!

–Steve

4th Year Project: Scraping Pages!

The first step to my project was to get the main information that I was going to display on my web page. As mentioned in the previous post, the two pages I want information from are the schedule of classes and the undergraduate calendar. I used Ruby to accomplish this, if you want more info on scraping with Ruby drop me a comment.

The information I needed to pull from the schedule of classes was the basics for each class including the department, the class name and number, the enrollment cap and total, what day/time it was schedule for and the instructor.  A quick inspection of the page demonstrated that it was very poorly design, no information had tagged IDs or anything useful in that way. After a little digging and with the help of this command:

ie.show_tables

I was able to ascertain that the schedule of classes page had 2 tables, with the second table containing ALL of the desired information on the page; now if this isn’t bad web design I don’t know what is!

Alright I was getting somewhere, the information is in a table, now it was just a matter of finding the right logic to catch the information I wanted. Again after a little investigation I found that the department name would appear in the first column of a given row, and after I caught the department name there was a concrete pattern to where the rest of the information I wanted was placed. The logic I ended up using (and excuse the lack of indenting, wordpress is being a pain) was:

size.times do

if(classArray[count][0] == dept)

Write desired information to an excel form (for the time being)

end

count = count+1 #Increase count so that it checks the next row

end

So this basically iterates through each department page and pulls down all of the information I need! I apply very similar logic to pull down all of the information from the Undergraduate calendar. As things stand I have all of the current information available to students in an excel sheet, this is only temporary, I will shortly be putting it in to a MySQL database so that I could start putting it with the Django framework!

As far as next steps, well that would be to start learning Python/Django and getting a development environment up to play with, should be fun!

–Steve

Fourth Year Systems Design Engineering Project: My uwaterloo classes

A little background is in order for those unfamiliar with engineering at waterloo. First off is to explain this whole fourth year project business. In not too much detail, the project is done in the fourth (and final year) of engineering at Waterloo and is something that is done by all all engineering departments. The project spans the last two school terms (8 months) and the only requirement is that it has an acceptable amount of engineering content.  Now as a student in Systems design (SYDE for short) I have already done two projects similar to this, the only real difference is that they only lasted 4 months instead of 8. The project is usually done in groups of at most 2-3 but I am going at my project alone.

The main problem that I have chosen to tackle revolves around the information that is available to students when they are attempting to find information on different classes that they could potentially take at UW. I have come up with a problem statement, which is part of my Design Plan , it is as follows:

Students at the University of Waterloo are subject to an undergraduate class system that is less
than ideal; information is disjoint, there are no reviews for classes, there is no search feature,
rendering it difficult to plan out a university career. A successful solution will allow a user to
easily and quickly ascertain the quality of a class and enable them to plan their university careers
such that a university student requires reduced effort in choosing courses.

I have told quite a few people about my project, and the first response from those outside of Waterloo is surprise at how inadequate the current system is. I personally have had tons of trouble with finding classes that I want to take. The only hard information that is offered is the schedule of classes that tells you when classes are and the undergraduate calendar which provides you with an at most 4 line description of a course. In my experience a four line, antiquated description of a course is not nearly sufficient when I am selecting a class that I am paying close to $1000 to take. This is jus the tip of the ice berg to the problems that are with the current system, for more details read over my design plan, or leave me a comment and I will be more than happy to elaborate.

The solution that I am planning to implement is another web based application, but one that addresses the major difficiencies that I see. My web application will allow users to: rate classes, upload course informaion, view the schedule along with the description in a single location, plan out their whole university career and search the database of classes. These are the main areas that I am focusing on for now, if I finish faster than I anticipate, then I will be tackling a few other issues that I have identified!

The plan is to create the web application using the Django framework, so it will mainly be python based. For scripting needs I will most likely be using Ruby because that is where I have the most experience. For database needs I anticipate using MySQL. I have actually already scraped all of the information that I require from the current uwaterloo pages and placed into an excel table, just until I get the MySQL database setup.

I will be making posts here and there about the project, the first most likely being on the scraping script as I feel some of the things I learned from it might be useful to others!  If you want more info check out my Design Plan.

–Steve