Author Archives: Michael Kölling

US now charges entry fee at the gate

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I just discovered that I now have to pay to enter the USA. Just like when entering Disney Land. But cheaper.

I am planning travel to the US again soon, and have been going through the paper work. For a very long time, travellers who entered the US on the Visa Waiver programme (i.e. most European countries) had to fill in a famous green form on the plane with some details. Then, at the beginning of last year, the US Customs and Border Protection Agency went modern: The paper forms were replaced with an online registration form collecting roughly the same data. (Well, for about a year we had to fill out both – the online and the paper form, but that’s been phased out now. The paper form is gone.)

Now, my ESTA registration, as it is called, has expired, and I have to apply for a new one. Which I just did. Only this time, it cost me $14.00.

The registration process now starts with this instruction in the first paragraph:

Before you begin this application, make sure that you have a valid passport and credit card available.

On the next page, it explains the interestingly named Travel Promotion Act (TPA) of 2009:

The Act directs the Secretary of Homeland Security to establish a fee for the use of the ESTA system, comprised of $10.00 for each VWP applicant receiving authorization to travel to the United States and $4.00 for the processing of the ESTA application. Applicants who are denied authorization to travel to the U.S. under the VWP will only be charged $4.00.

So, they are charging me four bucks for the pleasure of using a web form. And then a $10 entry fee if they decide to let me in. And I thought the point of using web interfaces to collect information was intended to make the process cheaper…

And we have to be careful in filling it in, too:

If information is entered incorrectly, the applicant may be charged additional fees to reapply.

I am not quite sure whether I should be annoyed at having to pay to cross a border into a country where I don’t require a visa (and having to pay for using a few hundred milliseconds of processor time on a web server!), or whether I should be happy to get all the delights of such a big country for only 10 dollars…

Sharing of teaching resources – it’s about people, not about stuff

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iconAt the beginning of April this year, we opened a new web site: the Greenroom.

The Greenroom is a web site where teachers who teach with Greenfoot can share resources and have discussions. It was clear for a while that sharing of resources was a powerful thing that was urgently needed for the Greenfoot community. Greenfoot is different from many other environments, teaching with it requires different projects and different ideas, and thus getting started with it, as a new teacher, is challenging. Having a community to talk to, to ask questions, to get ideas, to get tried and tested material, makes a huge difference.

Yet, this is a space where many have failed.

It is often said, with only slight exaggeration, that there are more teaching resource repositories than there are teaching resources. The fact is, countless resource repositories have been created, and most of them have tumbleweed blowing down the main street.

The typical pattern is this: A repository is opened, a flurry of activity follows, resources are submitted (often by the creators and other people personally involved or contacted), and then it dies down. A few months later, little is happening, resources are not maintained, few new resources are added, you can hear the cold wind blowing through empty spaces.

A high profile example is the repository of resources on the ACM SIGCSE website (one of the largest organisations in computer science education). It was – as far as I know – opened in early 2004, and initially attracted a good number of submissions. However, this quickly died down. Looking at the recent submissions, it seems that only four resources were submitted in all of 2008. This went down to three in 2009, with one single submission (so far) in 2010.

Now, I don’t want to pick on that one particular repository specifically. This pattern is not unsusual. I am pointing to it here as a typical example. Making repositories thrive is hard. (We have recently published a paper about this.) So, when we designed the Greenroom, we were very worried about meeting the same fate: spending a whole lot of effort in creating a repository site, only to have it die a slow, quiet death after a few short months.

I am happy to say that we seem to have avoided that fate. The Greenroom is alive and well.

From September 2009 to March 2010, the Greenroom existed as a Google Group. This gave us an excellent discussion forum, and quite poor storage of resources. Over these first six months, about 170 people signed up. Then, at the end of March 2010, we finished our custom implementation of the new Greenroom, and we were amazed at the result: even though only half of the Google Groups subscribers moved over, we surpassed the old subscriber numbers within two weeks, and then they continued to climb. Now, after eight months, we have about 900 people signed up. Lots of resources have been posted, and many interesting discussions are going on.

subscriber graph

Subscriber numbers of the Greenroom; old (red) and new (orange)

So, what makes this site work, when so many others have failed?

I think, in building such a site, you need to address a number of questions:

  • Who is allowed to upload resources? Everyone, or only trusted people?
  • How do you ensure quality? By prior review (work-intensive, hard), or do you let everything in (and risk flooding by poor quality, untried material)?
  • Do you restrict access? (If only teachers can access, you can also post exercises with solutions, exams, etc. But then you need verification.)
  • How do you maintain the resources? Who looks after them?
  • Do you store local copies of resources (which may go out of date) or links to outside resources (which may break)?
  • How do you organise searching and browsing? This requires relating resources to each other – who does that work?

And most importantly:

  • How do you make people come and submit interesting material, and participate in interesting discussions?

I think there are some design choices you can make to address many of these things. As a result, we have built a repository site that is quite different from others. We decided to not use a standard platform (because they only gave us the same old stuff that we didn’t want) and build our own from scratch. The main design choice, which makes most of the difference is this:

The site must be about people, not about stuff.

So we designed a site that is primarily about community, and then about material. There are many design details that embody this idea:

  • The main page of the site shows activities of people, not lists of things.
  • People sign up to the site, and have an ongoing relationship with it. It’s not something where you go once every two years when you redesign your course, it’s a place where interesting things are happening every week or maybe even every day.
  • People sign up with their real names, and are encouraged to post profile pictures. In the Greenroom, you move in a community of peers, not in a big, anonymous black hole.
  • The mental model is that of a staff room in a school, not of a library. It’s about meeting people, not about searching through piles of stuff.
  • Submitting unfinished resources is welcomed. We all know that most things never get finished – submitting something is better than submitting nothing.
  • The resources are owned by the community, not by single people. The edit rights follow a wiki model: everyone can edit everything. (I remember the moment in our design discussions when Neil Brown, one of our team members, suggested this. This changed almost everything. Many of the questions posted above are affected by this. Like many good ideas, it seems obvious in retrospect, but wasn’t at the time.)
  • Small contributions are welcome. Linking some related resources, for example, is a good thing. It’s quick, anyone can do it, and the wiki model allows everyone to do it.

In short: I think people should re-think teaching repository design. It has worked for us. (More details about this are in our paper.) There is daily activity in the Greenroom, many people visit regularly, we have frequent interesting discussion in our forum, and a large number of excellent resources. It has been going much better than we dared to hope.

So, if you think about designing a resource repository, think about the people, not about things. And if you are a teacher interested in Greenfoot, join the Greenroom. There are many friendly people there happy to help.

Highs and lows of flying in the USA

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I am on my way back home from a visit to the US right now. Two things just happened in the last few hours:

  1. On my flight from Atlanta to Boston, I had internet access on the plane! Woohoo! That was the first time for me that I saw that working. The previous blog post (“Comparing Scratch, Alice and Greenfoot”) was actually written and posted while at about 30,000 feet somewhere over the east coast of the US. I could actually escape watching the romcom they showed on the in-flight movie system, and do something interesting. (At least for me.) A toast to technological advancement!
  2. Going through security here in Boston (where I’m now sitting in an airport “pub”), I was selected to go through the backscatter scanner. As some people before me, I opted out. So I got a very intimate pat-down. Sigh.

Now, I really like visiting the US, but I’d feel a lot happier if I didn’t get treated like a criminal each time. The routine finger printing every time I enter here already rubs me up the wrong way, and now this.

Technology in used a good and in the wrong way.

Comparing Scratch, Alice and Greenfoot

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logosAt ITiCSE 2009 and again at SIGCSE 2010, we had panel session: Comparing Alice, Greenfoot and Scratch. The session came about because all three development teams – the Scratch, Alice and Greenfoot teams – were regularly asked one question: What’s the difference?

All three systems aim to let young people learn about programming. Many teachers (as well as parents or kids) have heard of more than one of them, but deciding which one to use can be difficult. While there are clear differences, the time it takes to evaluate all three of them is not trivial.

The panel session turned out to be very popular. The room was packed full, and we got plenty of questions afterwards. So we decided to create a written version of this session. And it’s now available.

We wrote a set of papers, which have now been published in a special issue of the ACM Transactions of Computing Education (TOCE). Each paper was written by a key member of the design team of one of the environments. The papers are more extensive and more in depth than the panel was (we all took the chance to write about various aspects our systems, which we had intended for some time, but never got around to doing), but they also aim to record some of the discussion that we had at the time.

Target age groups for Alice, Scratch and Greenfoot

The TOCE special issue consists of an introduction, three papers (one each) about the three environments, and a discussion section at the end. They are

(NOTE: All papers are available in the ACM digital library. ACM allows authors to also publish the papers on their own web sites. I will link to those freely available copies when they have been made available by the authors. So check back in a little while if you could not get all you were interested in.)

Greenfoot wins 2010 Premier Award

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We are very happy to hear that Greenfoot was awarded the 2010 Premier Award for Excellence in Engineering Education Courseware, a prize given to systems that show “high-quality, engaging, non-commercial learning innovations designed to enhance engineering education.”

Two systems are chosen annually by Engineering Pathway to receive the Premier Award, a prize that marks outstanding contributions in engineering software. Ian and Davin from our team made the trip to the Frontiers in Education Conference in Washington, D.C., to receive the award at a special “Premier Award Ceremony”.

This is the second award that Greenfoot has received (after winning the Duke’s Choice Award in 2007). But, of course, we don’t do all this for the awards. We just do it for all the the fame and money…

You can Save The World

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Earlier today I wrote about the new Greenfoot features. I forgot one: Saving the world.

In previous editions of Greenfoot, there was one annoying aspect: every time you had to recompile your classes, your interactively created objects disappeared. (This was not a bug: it is necessary, because the class implementing these objects does not exist anymore.)

This could be overcome by writing an initialiser method in the world class that creates and inserts all the objects you want to have in the world. This solves the problems, since objects get recreated automatically. However, writing these initialiser methods can be tedious.

So we come to the rescue: Saving the World.

You can now insert the objects you initially want in the world interactively, and then save the visible state of the world as the starting state of your program. Let’s look at an example.

Let us assume I want a scenario where the initial objects at the start of the game are a hamburger and three pigs. (Don’t ask). Let us further assume that I have just created the pigs and the hamburger interactively and placed them into my world. Figure 1 shows my world at this stage.

Figure 1: Three pigs and a hamburger

This is all well so far – with the problem that the actors will disappear (and I have to manually recreate them) after every compile.

Enter Save the World.

In Greenfoot 2.0, I can now select Save the World from the world context menu (Figure 2).

Figure 2: Saving the world

When I choose this function, Greenfoot writes the source code for a method called “prepare” into the class of the world object. This method contains code to create and insert objects just as they are in the world, and a call to this method from the world constructor (Figure 3).

Figure 3: The generated 'prepare' method

The effect is that next time, when I recompile my class and the world is re-created, the objects in the world are re-created as well. The status of the world is saved.

There are a few characteristics worth noting about this mechanism:

  • We consciously chose to create source code (rather than, say, serialising the world objects) because it can serve as a good learning instrument. Students can study the generated code and learn from it.
  • The source code of the automatically generated ‘prepare’ method may be freely edited by hand. There is not much special about this method, and you are welcome to adapt it in the editor in any way you feel like.
  • When the world was already saved, and you save it again, the prepare method will be adapted appropriately.
  • The prepare method will include code to recreate exactly what you did to construct the world. For example, if you create and place an object, and then move it, the prepare method will add the object at first at the same position where you first added it, and then move it. This is necessary, because the sequence may have had side effects. If you are only interested in the final position, you can streamline the prepare method manually by editing it (and taking out any unnecessary calls).
  • After the scenario has run, the world cannot be saved anymore.

(All screenshots in this post are produced by the author and are hereby placed in the public domain.)

Greenfoot 2.0 – The new features

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Yes! It’s here! It’s out!

Greenfoot 2.0 has just been released. After a lot of hard work, and about a month behind schedule, we finally completed the work on Greenfoot 2.0. Even though it may not be immediately obvious, this is one of the largest updates we have ever produced for Greenfoot. A lot of work has been done internally, and users will discover the effects of many of them over time.

Greenfoot splash screen

The Greenfoot 2.0 splash screen

New features are available in the editor, for processing and recording sound, for editing images, debugging your programs, and more. Here, I will summarise the most interesting changes (at least those that users can directly see – there are many internal improvements to performance and stability that I won’t discuss here).

The first thing users will notice after upgrading is a new splash screen. (Yes, we are now supported by the good folks at Oracle, instead of Sun Microsystems, after Sun was swallowed up by Oracle.)

But after that, it all might look rather underwhelming at first. The Greenfoot main window looks pretty much as it used to look before. “Where’s the new stuff?”, I hear you ask. Sharp-eyed users may notice one small change: the world name, that used to be shown above the world in the main window, is not there anymore.

The name of the world used to serve as a placeholder to represent the world object itself. It had a right-click functionality, that let you access the world object’s context menu to invoke instance methods on the world object itself. The problem was that this functionality was quite hidden, and many users never discovered it. It was bad UI design, since nothing in the name indicated that this was clickable. It had, in fact, almost easter egg-like quality.

We have now removed this name, and instead made the whole world area right-clickable. Right-clicking the world itself (or indeed the grey background behind it) will show the world object context menu and lets you invoke the world methods.

main window

The main window

Right-clicking in the world itself is more natural (more conforming to user expectations and more discoverable) and we expect that users will find this menu more easily now. (By the way, the reason that this was not done like this in the first place is that early versions of Greenfoot had different functionality attached to mouse clicks in the world.)

The next thing many users will discover is the new look of the editor.

The new editor

Greenfoot now incorporates the same editor that is used in BlueJ since the BlueJ 3.0 release earlier this year. The new features include scope highlighting, a new navigation view, better Find and Replace and code completion. (Code completion is activated by pressing Ctrl-Space.) I have described these features in more detail in an earlier blog post, when they came out with BlueJ – read them there if you want to know more..

greenfoot editor

The new Greenfoot editor

We expect that the new editor, especially the availability of code completion for Greenfoot API calls, will be a substantial improvement to the user experience. (I have been using it for a few months now, and I wouldn’t want to work without it anymore!)

Sound recording

sound recorder

The sound recorder

Greenfoot now has a built-in sound recorder. It can be found in the Controls menu, and you can now record your sounds directly from within Greenfoot. The functionality is very simple — just recording and trimming is supported — but this is what you need most of the time. If you want more sophisticated sound editing, you can still use third party applications (such as Audacity). However, the built-in recorder should be sufficient in many cases.

There is unfortunately a Java bug that cases problems with sound recording on some USB connected microphones. It works, however, with most microphones, and we hope that the remaining problems will be fixed in a future Java update.

But sound recording is not all that’s new with sound. You now also have more control over sound playback.

MP3 support

Yes, mp3 support! Greenfoot can now play mp3 files! Really. So go on and write your first MP3 player.

The GreenfootSound class

In previous Greenfoot versions, programmers had little control over how sounds are played. They could be started, but that’s all. Now, Greenfoot has a new class called GreenfootSound. It has method for starting, stopping and pausing sounds, as well as looping. This makes working with sounds much more flexible.

For short, simple sounds (such as sound effects), the Greenfoot.playSound(…) method is still the best to be used. But if you need more sophisticated functionality, create a GreenfootSound object and you can control the sound in more detail.

The debugger

Greenfoot now has a debugger built in. As some of you had discovered before, the code for the debugger has been there under the hood for some time (and there were ways to make it come up), but it was not working well, not supported, not finished, and had no proper interface.

debugger window

The Greenfoot debugger

Now you can open the debugger window from the menu, set breakpoints, stop the execution, single step through your programs and monitor your variable values. Especially for illustrating the working of control structures, this should be a useful help.

Image editing

Creating or editing images is a task that is very often part of developing Greenfoot scenarios. Now you can start creating or editing images directly from within the Greenfoot image dialogue.

image editing

Editing images

The action menu under the image list offers functions to edit, delete or create an image. This will happen in external applications. By default, Greenfoot will open the default application for the chosen file type on any platform. This behaviour can also be configured to select a specific application. (I will write in more detail about some of these new functions in separate posts soon – I’ll discuss how to do this then.)

When images are created, they are automatically placed into the scenario’s images folder, so that they are immediately available for use in Greenfoot.

Unbounded worlds

The last bit of functionality I’ll talk about today are unbounded worlds.

As you know (if you have used Greenfoot in the past), actors cannot leave the world. When they try to move beyond world boundaries they are simply placed at the edge of the world. Breaking out is impossible for them. This has good reason: if actors were to leave the visible world, it can be very hard to get them back. You cannot interact with them anymore, and you don’t really know where they are. In fact, you may not even be aware that they are still there. This has great potential of confusion and difficulty for beginners.

This behaviour remains the default in Greenfoot 2.0 — but you can now configure your world to allow actors to leave the visible area for specific scenarios, should you want to do that. (And we know that some of you do: many of you have asked for this for some time!)

The world is then essentially infinite in all directions, and the visible world in the Greenfoot window is just a viewport into a small part of this eternal universe.

The World superclass now has a second constructor that allows the bounds to be removed:

Constructor Summary
World(int worldWidth, int worldHeight, int cellSize)
Construct a new world.
World(int worldWidth, int worldHeight, int cellSize, boolean bounded)
Construct a new world.

The first constructor is as before. Thus, you old code will work unchanged. For example, a world constructor

public AntWorld()
{
    super(500, 400, 1);
}

will work as before and create the usual bounded world. However, you can now also use

public AntWorld()
{
    super(500, 400, 1, false);
}

In this case, actors will be allowed to leave the visible world and walk as far away as they like. For some type of games this will be very useful. When out of the visible world, they will still act, cause collisions, etc. You just cannot see them.

And so…

So, plenty of new stuff in Greenfoot 2. The last thing to tell you is where to get it. And that is, of course, where it has always been: www.greenfoot.org.

Install it, take it for a spin, and let us know what you think. We’d love to get your feedback. Bug reports, of course, but also things you like. You comments are one of the inputs that drive our future development.

And most of all, as always: Have fun programming!

Update:

I forgot to mention one new feature: Saving the world. I have now described this in a separate blog post.

Greenfoot on Twitter

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Twitter logoIn a bold attempt to keep up with the times, and trying to not appear to be the bunch of old dinosaurs which we actually are (in internet age, at least), Greenfoot is now on Twitter.

None of us really knows very much about this, but apparently this is what one does nowadays. So now you have the unique chance to follow the GreenfootTeam and find out first hand why releases are delayed, bugs pop up, and how software somehow still gets released eventually.