Sequence Diagram by Charles Babbage

Charles Babbage designed the Analytical Engine, a mechanical computer, in the 19th century. Only a partial trial model was built when he died in 1871:

In his 1826 paper, On a Method of Expressing by Signs the Action of Machinery, he explains the need for a graphical modeling language in his project:

The difficulty ... induced me to seek some method by which I might at the glance of the eye select any particular part, and find at any given time its state of motion or rest, its relation to the motions of any other part of the machine, and if necessary trace back the sources of its movement through all its successive stages to the original moving power.

Babbage later stated:

Without the aid of this language I could not have invented the Analytical Engine; nor do I believe that any machinery of equal complexity can ever be contrived without the assistance of that or some other equivalent language.

In the paper he uses a clock as an example:

The diagram below shows, in the middle columns (READING OFF PART), the hands of the clock (Hour, Minute and Seconds) and to the left the parts (TIME PART) connected to them. The time parts are labeled with the letters you can also find in the drawing of the clock mechanism above.
In the ORIGIN OF MOTION rows in the diagram you find arrows indicating the interactions between the parts. The lower half of the diagram shows a vertical time line with indications of the activity (active, direction of motion, variable speed...) of each part.   
It is interesting to note how close this resembles UML's sequence diagram is, with its object lifelines, message exchange arrows and activation boxes.

Here's an example of a UML Sequence diagram:

google anniversary doodle

Google 17th anniversary doodle showcases lego cabinet of the first google server at Stanford:

Astah: fast modeling

Astah (formerly Jude) is a uml tool that works very well, I only have some minor remarks about the interface:

• did not find a way to make an element unselectable (e.g. when you do not want to multiselect all elements in a package, but not the package itself), like you can in Enterprise Architect.
• you easily select sub-elements when you want to select e.g. a class

Here is a page with some tips for fast modeling from Astah, and a link with keyboard shortcut.
Some more tips

• Association classes: right click on an association, choose convert to association class 

Sequence diagram modeling does not have the same level of perfection in v7.0:

• Astah is in message draw mode, even when not appropriate (if you misclick you add an unwanted message)
• not easy to add methods from diagram to existing classes
• no automatic generation of communication diagrams from sequence diagrams (and vice versa) 
• unlike sequence diagrams, communication diagrams do not
• prompt to add new classes
• support iterations

model translation dictionary

Speaking in tongues: Nice translation dictionary from one modeling notation to another by Scott Ambler

Canon pixma mp510 ink absorber almost full / Canon pixma mp510 absorptiekussen bijna vol

IMy printer showed me this error message: Canon pixma mp510 ink absorber almost full. Please contact the service center.
Here's how I dealt with it:

What is the problem? 

Your printer performs head cleaning by forcing ink through the heads to remove dirt. This ink goes into the waste ink tank, which fills up.
Your printer does not really measure this, but when the page printing counter goes over a threshold it displays this message. You can press OK to make the message go away, but when the counter goes over a second threshold, the message will become: "ink absorber full" and you cannot print anymore.

Contacting the service center will cost you more than a new printer, so basically this message says: this printer is designed to fail, buy a new printer.

Option: replacing the print absorber

If you want to play "self-service" center, you can find the service center manual, with all instructions here. Here's the manual section on partial replacement of the main absorber:

I did not actually try this, but google says you can try to extend the life of your absorber pads by washing, drying and putting them back.

Resetting the counter

Next you need to reset the counter.
More often then not, the waste thank is not full at all, so you can risk just resetting the counter.
Here be dragons: when the tank really fills up, the printer might spill quite some ink!


I did not succeed resetting the counter with the instructions in the service manual (go into service mode, press reset four times, press power).

However I had success with this method from tricks-collections (actually for mp520):

1. Switch printer off
2. Press OK/BW copy/RESET simultaneously (1/2/3 in picture below)
   
3. Press on/off (button 4) while keeping the above buttons pressed.
4. When printer is on, release buttons 1/2/3
5. This might actually be enough, but just to be sure I pressed buttons 1/2/3 while i switched the printer off again.
   

Java 9 JShell

Jshell (developed in project Kulla) is a java shell allowing you to type java instructions at the shell prompt and have them executed.

• if jshell detects a complete statement even without a closing semicolon
• you can type an expression which will be evaluated 

-> 2 + 2
| Expression value is: 4
| assigned to temporary variable $1 of type int

• you are not obliged to catch exceptions
• you can save and load your command history
• you can use methods and references that will only be defined later

-> double volume(double radius) {
>> return 4.0 / 3.0 * PI * cube(radius);
>> }
| Added method volume, however, it cannot be invoked until method cube(double), and variable PI
are declared

• you can list current variables, methods...
•  tab completion as you type

Here's a small tutorial.

Windows 10 upgrade: login fails

After upgrading to windows 10 my password was not accepted !?
Issue: Windows had changed my default keyboard layout to US/Eng, which did not match my keyboard.
This is a setting you can change in the right bottom corner of the login screen, issue solved:

Some people also use their keyboard driver, the on-screen keyboard can help here: