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Posts Tagged ‘Computer Science’

Google Summer of Code 2010

Posted in Computer Science, Peer Relationships, Software Engineering, tagged , , , on 6 April 2010| Leave a Comment »

Last year, I had a great time participating in the Google Summer of Code with the Debian project. I had a neat project with some rather interesting implications for helping developers to package and maintain their work. It’s still a work-in-progress, of course, as many projects in open source are, but I was able to accomplish quite a bit and am proud of my work. I learned quite a bit about coding in C, working with Debian and met some very intelligent people.

My student peers were also very intelligent and great to learn from. I enjoyed meeting them virtually and discussing our various projects on the IRC channel as the summer progressed and the Summer of Code kicked into full swing. The Debian project in particular also helps arrange travel grants for students to attend the Debian Conference (this year, DebConf10 is being held in New York City!). DebConf provides a great venue to learn from other developers (both in official talks but also unofficial hacking sessions). As the social aspect is particularly important to Debian, DebConf helps people meet those with whom they are working with the most, thereby creating lifelong friendships and making open source fun.

I have had several interviews for internships, and the bit of my work experience most asked about is my time doing the Google Summer of Code. I really enjoyed seeing a project go from the proposal stage, setting a reasonable timeline with my mentor, exploring the state of the art, and most importantly, developing the software. I think this is the sort of indispensible industry-type experience we often lack in our undergrad education. We might have an honours thesis or presentation, but much of the work in the Google Summer of Code actually gets used “in the field.”

Developing software for people rather than for marks is significant in a number of ways, but most importantly it means there are real stakeholders that must be considered at all stages. Proposing brilliant new ideas is important, however, without highlighting the benefits they can have for various users, the reality is that it simply will not gain traction. Learning how to write proposals effectively is an important skill and working with my prospective mentor (at the time – he later mentored my project once it was accepted) to develop mine was tremendously useful for my future endeavours.

The way I see the Google Summer of Code is, in many ways, similar to an academic grant (and the stipend is about the same as well). It provides a modest salary (this year it’s US$5000) but more importantly, personal contact with a mentor. Mentors are typically veterans in software development or the Debian project and act in the same role as supervisors for post-graduate work: they help monitor your progress and propose new ideas to keep you on track.

The Debian Project is looking for more students and proposals. We have a list of ideas as well as application instructions available on our Wiki. As I will be going on internship starting May, I have offered to be a mentor this year. I look forward to seeing your submissions (some really interesting ones have already begun to filter in as the deadline approaches).

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Software Licensing and Copyright

Posted in Computer Science, Software Engineering, tagged , , , , on 20 October 2009| Leave a Comment »

One of the most often overlooked–yet arguably most important–issues in software development is copyright and licensing of works. In particular, I will discuss how this affects the open source software community with relevance to the Debian project.

As with any artistic or creative works, software is protected by copyright and its use is often governed by some sort of license. Please note that I am not a lawyer and I am not qualified to give legal advice, so take my suggestions with a grain of salt and please do leave a comment if you know something that I don’t.

A license is a legal contract that permits end users use of software under agreed-upon guidelines. In the open source community, licenses protect the integrity of free software by ensuring that they continue to remain freely available. For example, the GNU General Public License (GPL) stipulates that any derivative works of GPL-licensed code must distribute source code back to the community, which enables a two-way sharing of information between the originating software developers and the others who benefit from their work. Other licenses, such as the BSD License, are more liberal and do not have this restriction, but do have a disclaimer of warranties which shields authors from unintended legal consequences of their work.

Though licensing is probably the most important document detailing the relationship of the supplier (software developer or team) and other users, it cannot mean anything without copyright. In general, it is most useful to provide a copyright statement somewhere in resulting packages. A copyright statement is what allows authors to assert a particular license in the first place.

Moreover, license terms can only be changed when all copyright holders agree to the change. Unless you are explicit in your copyright conditions in the beginning, this can lock your project in to an undesirable license.

To make matters even more complicated, the Berne Convention for the Protection of Literary and Artistic Works (or simply Berne Convention as it’s most often called) describes a mechanism by which copyright is automatically in force upon creation of a work, even if the author does not explicitly assert it. For software, this effectively means that anyone who contributes any code is automatically the copyright holder on their contribution, which means that things quickly get complicated when there are many authors and contributors involved.

In Debian, we cannot and do not distribute software without knowing copyright information (including years of copyright, names, e-mail addresses where people can be reached, or a web site in the case of an incorporated entity). This is pursuant to the Debian Free Software Guidelines (DFSG), which require that we distribute only “free” software in our main repository–it’s part of our Social Contract.

In this regard, I would make the following recommendations:

  1. When beginning any project (open source or not), include a copyright statement immediately. It will eventually become a force of habit; this is a very good thing, and will pay dividends in the future.
  2. Establish a policy whereby contributors are asked to assign you copyright of their work; make a note of this somewhere in your documentation. Better yet, if you are part of an incorporated entity, assign copyright to that entity.
  3. Be explicit about your licensing terms and make sure to include copies of the license with your software. This helps to resolve ambiguities where there are several derivatives of a license (occasionally, developers license software under the BSD License without specifying which version they mean)
  4. Be wary of the “Public Domain” — this is an even more contentious issue than choosing an appropriate license. It is probably preferable to use a non-restrictive license such as the aforementioned BSD License (and its variants) or the MIT/X11 license, which is even more permissive.

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Debian Perl Packaging: Where I Lied

Posted in Computer Science, Software Engineering, tagged , , , , , , , , , on 15 July 2009| Leave a Comment »

Okay, so this is a long-awaited follow-up to my first post on the topic of  Debian Perl Packaging. Some of you might note I was pretty extreme in the first post, which is partially because people only really ever respond to extremes when they’re new to things. When you first begin programming, the advice you get is “hey, never use goto statements” — but as your progress in your ability and your understanding of how it works, what it’s actually doing in the compiler — then it might not be so bad after all. In fact, I hear the Linux kernel uses it extensively to provide Exceptions in C. The Wikipedia page on exception handling in various languages shows how to implement exceptions in C using setjmp/longjmp (which is essentially a goto statement). But I digress.

Back to the main point of this writeup. Previously I couldn’t really think of cases where packaging your own modules is really all that useful, especially when packaging them for Debian means that you benefit many communities — Debian, Ubuntu, and all of the distributions that are based on those.

During a discussion with Hans Dieter Piercey after his article providing a nice comparison between dh-make-perl and cpan2dist. (Aside: I feel like he was slightly biased toward cpan2dist in his writeup, but I’m myself biased toward dh-make-perl, so he might be right, even though I won’t admit it.)

I’m really glad for that article and the ensuing dialog, because it really got people talking about what they use Debian Perl packages for, and where it is useful to make your own.

Firstly, if you’ve got an application that depends on some Perl module that isn’t managed by Debian, but you need it yesterday, then you can either install that module via CPAN or roll your own Debian package. The idea here is to make and install the package so you can use it, but also file a Request For Package bug at the same time — see the reportbug command in Debian, or use LaunchPad if you’re on Ubuntu. This way, when the package is officially released and supported, you can move to that instead, and thus get the benefits of automatic upgrades of those packages.

Secondly, if you’ve got an application that depends on some internally-developed modules, then they probably wouldn’t exist on CPAN (some call this Perl code part of the DarkPAN), except in the rare case that a company open sources their work. But corporations will never open source all of their work, even if they consider the implications of providing some of it to the open source community, so at some point or another you’ll need to deal with internal packages. Previously, the best way to handle this was to construct your own CPAN local mirror, and have other machines install and upgrade from it — thus your internal code is easily distributed via the usual mechanism.

One of the advantages of using CPAN to distribute things is that it’s available on most platforms, builds things and runs tests automatically on many platforms. CPANPLUS will even let you remove packages, which was one of the main reasons I am so pro-Debian packages anyway. However, it does mean you’ll need to rebuild the package on other systems, which is prone to failures that cost time and money to track down and fix. CPAN and CPANPLUS are the Perl tradition of distributing packages.

If you are using an environment mostly with Debian systems, however, you may benefit from using a local Debian repository. This way, you only need to upgrade packages in your repository, and they’ll be automatically upgraded along with the rest of your operating system (you do run update and upgrade periodically right?). There is even the fantastic aptcron program to automate this, so there’s really no excuse not to automatically update.

In either case, creating a local package means you will be able to easily remove anything you no longer need via the normal package management tools. You can also distribute the binary packages between machines — though it sometimes depends on the platform (for modules that incorporate C or other platform-specific code that needs to be rebuilt). Generally, most Perl modules are Pure Perl, and thus you can compile and test it once, on one machine, and distribute it to other ones simply by installing the .deb package on other machines. You can copy packages to machines and use dpkg to install them, or better yet, create a local Debian mirror so it’s done automatically and via the usual mechanism (aptitude, etc.)

In conclusion: if you’re going to make your own Debian packages, do so with caution, and be aware of all the consequences (positive and negative) of what you’re doing. As always, a real understanding of everything is necessary.

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