Fair(ish) Use: Parity Error Trick

As I’ve mentioned in our Hangouts I’m preparing to teach AP Computer Science Principles this coming 2016-2017 school year. So, when I’m not doing work for ED 654, I’m in the depths of a computer science crash course. Luckily for all of you, there are some pretty cool topics I’m learning about and I picked my current favorite to share for this assignment.

The Parity Error Magic Trick

Cartoon animation showing steps of the parity error trick. Teacher closes eyes while student flips a random tile. Teacher turns around and examines the grid. Teacher correctly identifies which tile the student flipped over.

Image Source: CS Unplugged

To perform the parity error magic trick hand the stack of cards over to a student and ask them to lay out the cards face-up or face-down however they’d like in a grid pattern (or have them flip cards in a pre-set grid). Once the students are done, the teacher uses the remaining cards to create an extra row and column of cards on the grid. The teacher then turns their back, and the student flips any card in the grid. When the teacher turns around they should be able to spot which card in the grid has been changed.

This video demonstration of CS Unplugged’s “Error Detection Card Trick” activity was created by Jennifer Rosato for the Mobile CSP lesson on Error Detection:

Memory, magic, or some good ol’ parity error detection?

Solution: First, face-down cards are assigned 0s, and face-up cards are assigned 1s (see how we’re working those binary digits in?). For each row and column there are either going to be an even number of 1s or an odd number of 1s. The teacher decides whether they are going to run an “even parity” or an “odd parity.” For the sake of this example let’s assume it’s an even parity. The trick is in the extra row and column that the teacher adds to “make it more difficult” which actually isn’t random at all. If the students has placed 3 face-up cards in a row then the row is odd, but since we’re working with an even parity the teacher will make the row even by placing an extra face-up card in that row. Every row and column are made even with the extra parity cards that the teacher lays down.

When the student flips one of the cards while the teacher’s back is turned it creates a parity error. Now there will be a row and column that no longer have an even number of 1s. All the teacher has to do is locate where the odd row and the odd column intersect to correctly find the flipped card.

Parity error detection can also be used to help solve riddles like the one in this animation created by Alex Gendler for TED-Ed:

Parity Error Detection in Coding

I only understand parity error detection in its simplest form, so what follows is the entirety of what I know. If everything is made of transmitted bits (1s and 0s), there’s bound to be an error once in a while. Adding redundant parity bits to a code, allows for a basic form of error detection without altering original code. In a 1-bit parity, the redundant bit is placed in the leftmost position. Originally the redundant parity bit was added to a 7-bit string, making an 8-bit byte: 0011 1010. 1-bit redundancy (like putting a card at the end of a row) is able to detect an error but is unable to locate and correct it. The information would need to be retransmitted. Another downside of 1-bit redundancy is that it only flags an odd number of errors. For example, if it were an even parity byte 1010 0101 and two of those bits were flipped 1010 1111 it wouldn’t flag an error because the even parity is still true.

But fear not! 1-bit redundancy is not the only kind of parity error detection. Say hello to the Hamming Code. The Hamming Code uses a 3-bit redundancy for every 4 bits of code. Not only does this code allow for error detection, but also error correction. Through this technique three of the original bits are checked against each of their corresponding parity bits, and if they don’t fulfill the parity, the error in the original data bits can be corrected. This video from Khan Academy does an excellent job of breaking this down:

“NOTE: All Khan Academy content is available for free at www.khanacademy.org”

Error correction: How can we communicate in the presence of noise?


Fair Use of Materials:

I’m always especially nervous about using videos I find online, so I pushed myself to use more videos in this assignment and do a little digging to see how the owners would like them to be used.

Card Trick Cartoon – At the bottom of the CS Unplugged site they had posted “The CS Unplugged material is shared under a Creative Commons BY-NC-SA 4.0 licence.” I clicked on it to see what that actually meant, and I felt that I could work with those terms so that I could use the image in my post. I made sure to include attribution with the image.

Four Factors of Fair Use

Purpose & Character: I used the image for non-commercial purposes in an educational post that was meant to elicit new commentary. It was also placed in a broader conversation about parity error detection beyond the card trick.

Nature of the Copyrighted Work: This image was a creative work, but because it was posted as CS Unplugged material it falls under their CC license, so I’m still in the clear.

Amount and Substantiality of the Portion Taken: I used the whole image that was provided on the site, but again their CC license allows for this.

Effect of the Use upon the Potential Market: CS Unplugged doesn’t make a profit off of their online curriculum, and I’m not making any money from my blog.

Error Detection Card Trick (video) – It took me a while to figure out how exactly to use this video fairly. I first saw the video in a lesson on Error Detection in the Mobile CSP online curriculum (which is open source). But, when I went to the video itself to embed it, the owner of the video was one of my mentors for the course and I received a warning that looks like this: Screenshot of a YouTube warning saying "This video is unlisted. Be considerate and think twice before sharing."

So, of course, I thought twice before sharing. First I checked to see what kind of license the online Mobile CSP material has, which ended up being a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International license. I knew that I should be able to use the video because it had been uploaded onto the Mobile CSP site and was covered by the CC license. But, I still felt weird about it, so I wrote an email to my mentor to get her permission to use the video in this post.

Four Factors of Fair Use

Purpose & Character: I used the video for non-commercial purposes in an educational post that expanded the discussion around the content and elicited new commentary.

Nature of the Copyrighted Work: I wouldn’t consider this video to be creative because it is a demonstration of a card trick, and doesn’t contain original material.

Amount and Substantiality of the Portion Taken: I included the entire video in my post.

Effect of the Use upon the Potential Market: Mobile CSP curriculum is open source and does not sell their material so there was no profit lost from my use of the video.

Can you solve the prisoner hat riddle? (video) – To see how I could use this video I first checked out the TED Video Usage Policy. It looks like TED Talks are under a Creative Commons license Attribution – NonCommercial – NonDerivative. But, then after that section was information specifically about TED-Ed, which doesn’t fall under CC, but instead under YouTube’s Standard Policy. I’m not sure why they have some of their videos hosted on the TED site and other hosted through YouTube. How can they really support their tagline of “Ideas Worth Sharing” if their whole education outfit isn’t under CC?

Four Factors of Fair Use

Purpose & Character: I used the video for a non-commercial purpose in a way that expanded on the ideas in the video and brought it to a new group of people for commentary.

Nature of the Copyrighted Work: The idea in the video isn’t creative as it is a well known riddle, but the art in the video was creative. I provided adequate attribution to the creator and to TED-Ed.

Amount and Substantiality of the Portion Taken: I used the whole video (because using half of a riddle kind of takes the fun out of it…). But since the other TED videos are non-derivative, I think it may actually be in my favor that I used the whole video.

Effect of the Use upon the Potential Market: As the video was already being shared through TED-Ed who encourages their videos to be distributed, the creator would not have been making a profit from the video. Unless he was making money through YouTube, in which case I’m just providing more hits for him. I’m not making a profit by having the video embedded in my blog.

Error correction (video) – Khan Academy has a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States license for all of their online material. They also have a thorough FAQs section about how/when/where you can use their material. I specifically looked at “I would like to embed your videos on my site. Is that allowed?” Along with adhering to their CC license, they also asked that embedded videos use the Khan Academy player and to include their “NOTE” about all Khan Academy material being free on their website.

Four Factors of Fair Use

Purpose & Character: My use of the video was non-commercial. There was value added to the video by placing it in conversation with the other parity bit information contained in the post, and made it accessible for new commentary.

Nature of the Copyrighted Work: While the information wasn’t creative (non-fiction) the video animation certainly was creative, but the video is covered under Khan Academy’s CC license.

Amount and Substantiality of the Portion Taken: I used the whole video that was posted on the Khan Academy site, but again, the material is covered under CC.

Effect of the Use upon the Potential Market: Khan Academy makes it very, very clear that their material/curriculum is free and want it to remain free (hence posting the NOTE before the content). So neither of us make any money off of posting the video.

Work Together – Minecraft Social Contract

For the “Work Together” assignment, Philip Peterson and I developed discussion questions that could be used in the classroom to create social contracts for virtual Minecraft communities. We started with the questions that I use in my own classroom to develop social contracts (as directed through the “Capturing Kids’ Hearts” program) and adapted/rewrote/expanded them for guiding a virtual community.

IP: Friend or Foe

The thing about writing limericks is that if you write a great, great limerick people will remember it but they will forget the name of the person who wrote it, and that’s okay. The permanence of anonymity, the immortality of the anonymous. Long live the jokes and who cares who thought them up. They are permanent. And if years from now you should see “The young fellow from Pocatello…” in a collection of verse, or written on a toilet stall, it’ll be anonymous even though I wrote it in a hotel room once in Pocatello, Idaho, and that’s okay. (Keillor, 15:48)


This past Saturday was Garrison Keillor’s last performance as the host of the beloved radio program “A Prairie Home Companion.” And I won’t lie, I’m taking it pretty hard. At the end of his final “News from Lake Wobegon” segment, Keillor talked about his love of limericks and how if his only legacy is a limerick written on a bathroom stall making young boys laugh, that would be enough for him, because “what more could you hope for?” (16:52).

Headshot of Garrison Keillor.

By Prairie Home Productions, Attribution, https://commons.wikimedia.org/w/index.php?curid=6753486

To wrap Keillor’s closing sentiment into our discussion of intellectual property, I think our current laws would show that we often do hope for more when we publicize our ideas. We may want to reap the benefits. We may want recognition. We may want to hang on to some semblance of control. This is not to say that it is wrong to hope for these things, but as someone who has been conditioned to believe ownership over ideas is the norm, I was struck by Keillor’s emphasis on anonymity. Keillor’s statement comes across as generous, as selfless; he is providing joy to future generations and is seemingly content with his name being lost to the wind. He doesn’t need credit. He doesn’t want profits from the royalties. Maybe it will inspire more young boys to write semi-inappropriate limericks and cause more people to laugh on a podcast one day.

This makes me wonder, “Would this be enough for me?” What if instead of a limerick, it was a technological innovation. Would I have it in me to willingly share my ideas to the benefit of others and not just myself, especially if there were a monetary profit up for grabs.

What interests me about intellectual property isn’t the nitty-gritty legal details, but the human motivations behind it. My example above of relinquishing rights over a limerick may be silly (a low-value piece of intellectual property), but I think it demonstrates how quickly an idea (once shared) can disseminate and lose attribution, and Keillor shows us one way a person can respond in that situation. He hopes that his work inspires others, becoming a vehicle for future innovation. We anticipate a joke being something we share freely and lose nothing in the telling. So, why do we feel this way about some ideas and not others? Money? Acknowledgment? And at what point do you weigh personal gain against the benefit of a wider population?

The peril of intellectual property is that it isn’t tangible: it isn’t land you can sign papers on, or an object to lock away in a safe. According to Steven Kinella in his 2008 article “Against Intellectual Property”, property laws only make sense when we’re dealing with conflicts over resources and scarcity, “The very possibility of conflict over a resource renders it scarce, giving rise to the need for ethical rules to govern its use. Thus, the fundamental social and ethical function of property rights is to prevent interpersonal conflict over scarce resources.” But can an idea be “taken” or “stolen” if it has been made accessible by the originator? Do you have less of your intellectual product once others get their hands on it as well?

Front cover of the book "Blown to Bits". Two hands holding a globe.

Image Source: www.bitsbook.com

I just started reading a book entitled “Blown to Bits” (2008) that tackles issues surrounding the digital explosion, and intellectual property happened to show up in the introductory chapter. In their example, the problem is not that we’re able to make copies of online material, but that we’re able to make perfect copies. A perfect copy means there is no need for the original and in fact, “even the notion of “original” is meaningless” (p. 7). Once something is digitized it becomes “bits,” or binary digits: text, photos, audio, movies, and software. They can be perfectly recreated, but this doesn’t mean the originator is suddenly lacking bits: the property doesn’t go “away.” They sum this concept up nicely saying, “But bits are an odd kind of property. Once I release them, everybody has them. And if I give you my bits, I don’t have any fewer” (p. 7). An “odd” kind of property, or maybe not property at all.

So, our laws may be slow on the uptake that intellectual property is not the same as tangible property, but I would guess that this is going to be a gradual, snail’s pace, change. But there seem to be some companies who are finding ways to bridge the gap between the two. For instance, Tesla. In a recent Forbes article, Elon Musk discussed the decision to have an open-source policy with their software saying, ““Technology leadership is not defined by patents, which history has repeatedly shown to be small protection indeed against a determined competitor, but rather by the ability of a company to attract and motivate the world’s most talented engineers” (p. 3, 2016). Tesla retains the patents for their battery, but allows their software to be open-source. By doing this, Musk attention is not on hiding a secret formula from his rivals, but on the top-notch developers who are drawn to the software and can make the product better. Can you imagine? A business philosophy that focuses on collaborators instead of competitors.

Wing It! – Infomagical Challenge

**Similar to my last Wing It, I’ll be completing this challenge this coming week (7/4-7/8) and would love to have some Wingmen onboard! 

Note to Self logo. Dark colored head with multi-colored patterns exploding from the top.

Image Credit: www.wnyc.org

Thanks to Manoush Zomorodi and the podcast “Note to Self,” here is another week-long challenge. Like Bored and Brilliant, the Infomagical challenge encourages listeners to be better consumers of online information. Some of us may have FOMO (Fear of Missing Out), so we breeze over articles, stories, and headlines without ever really retaining any useful information. How could we make our online information browsing more productive, and more importantly, use it to support our personal goals?

Objective: At least for a week, let’s try to fight information overload by paying attention to what we’re doing online, and the gadgets that get us there.

Assignment: Nousion-ites! You can do this! The challenges and corresponding short podcasts can be found here. Listen to the podcast or read through the new challenge every morning this week. If you don’t think you’ll remember, sign up for text or email reminders here. Take notes on your experience and create a mini-reflection (text, audio, video, etc) for each day, then wrap it all up and you can post at the end of the week for a Wingman assignment.

Points:  15 /15

My infomagical journey:

Infomagical Day 5: My note to self – 

george