Geelong Libraries by branch – a data visualisation

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At a glance


Geelong Regional Libraries Corporation (GRLC) came on board GovHack this year, and as well as being a sponsor, opened a number of datasets for the hackathon. Being the lead organiser for GovHack, I didn’t actually get a chance to explore the open data during the competition. However, while I was going for a walk one day – as it always does – I had an idea around how the GRLC datasets could be visualised. I’d previously done some work visualising data using a d3.chord layout, and while this data wasn’t suitable for that type of layout, the concept of using annulars – donut charts – to represent and compare the datasets seemed appealing. There was only one problem – I’d never tackled anything like this before.

Challenge: accepted

Understanding what problem I was trying to solve

Of course the first question here was what problem I was trying to solve (thanks Radia Perlman for teaching me to always solve the right problem – I’ll never forget your LCA2013 keynote). Was this an exploratory data visualisation or an explanatory one? This led to formulating a problem statement:

How do the different Libraries in the Geelong region compare to each other in terms of holdings, membership, visits and other attributes?

This clearly established some parameters for the visualisation: it was going to be exploratory, and comparative. It would need to have a way to identify each Library – likely via colour code, and have appropriate use of shapes and axes to allow for comparison. While I was tempted to use a stacked bar chart, I really wanted to dig deeper into d3.js and extend my skills in this Javascript library – so resolved to visualise the data using circular rings.

Colour selection

The first challenge was to ensure that the colours of the visualisation were both appealling and appropriate. While this seems an unlikely starting place for a visualisation – with most practitioners opting to get the basic shape right first, for this project getting the colours right felt like the best starting point. For inspiration, I turned to the Geelong Regional Library Corporation’s Annual Report, and used the ColorZilla extension to eyedropper the key brand colours used in the report. However, this only provided about 7 colours, and I needed 17 in order to map each of the different libraries. In order to identify ‘in between’ colours, I used this nifty tool from Meyerweb, which is super-handy for calculating gradients. The colours were then used as an array for a d3.scaleOrdinal object, and mapped to each library.

var color = d3.scaleOrdinal()
        "Geelong West",
        "Waurn Ponds",
        "Ocean Grove",
        "Mobile Libraries",
        "Barwon Heads",
        "Western Heights College"

Annular representation of data using d3.pie

Annular representation of data - step 1
First step in annular representation

The first attempt at representing the data was … a first attempt. While I was able to create an annular representation (donut chart) from the data using d3.pie and d3.arc, the labels of the Libraries themselves weren’t positioned well. The best tutorial I’ve read on this topic by far is from data visualisation superstar, Nadieh Bremer, over on her blog, Visual Cinnamon. I decided to leave labels on the arcs as a challenge for later in the process, and instead focus on the next part of visualisation – multiple annulars in one visualisation.

Multiple annulars in one visualisation

Annular representation of data - step 2

The second challenge was to place multiple annulars – one for each dataset – within the same svg. Normally with d3.js, you create an svg object which is appended to the body element of the html document. So what happens when you place two d3.pie objects on the svg object? You guessed it! Fail! The two annulars were positioned one under the other, rather than over the top of each other. I was stuck on this problem for a while, until I realised that the solution was to place different annulars on different layers within the svg object. This also gave more control over the visualisation. However, SVG doesn’t have layers as part of its definition – objects in SVG are drawn one on top of the other, with the last drawn object ‘on top’ – sometimes called stacking . But by creating groups within the BaseSvg like the below, for shapes to be drawn within, I was able to approximate layering.

var BaseSvg ="body").append("svg")
    .attr("width", width)
    .attr("height", height)
    .attr("transform", "translate(" + (width / 2 - annularXOffset) + "," + (height / 2 - annularYOffset) + ")");

  Layers for each annular

var CollectionLayer = BaseSvg.append('g');
var LoansLayer      = BaseSvg.append('g');
var MembersLayer    = BaseSvg.append('g');
var EventsLayer     = BaseSvg.append('g');
var VisitsLayer     = BaseSvg.append('g');
var WirelessLayer   = BaseSvg.append('g');
var InternetLayer   = BaseSvg.append('g');
var InternetLayer   = BaseSvg.append('g');
var TitleLayer      = BaseSvg.append('g');
var LegendLayer     = BaseSvg.append('g');

At this point I found Scott Murray’s SVG Primer very good reading.

Annular representation of data - step 3
The annulars are now positioned concentrically

I was a step closer!

Adding in parameters for spacing and width of the annulars

Once I’d figured out how to get annulars rendering on top of each other, it was time to experiment with the size and shape of the rings. In order to do this, I tried to define a general approach to the shapes that were being built. That general approach looked a little like this (well, it was a lot more scribble).

General approach to calculating size and proportion of multiple annulars
General approach to calculating size and proportion of multiple annulars

By being able to define a general approach, I was able to declare variables for elements such as the annular width and annular spacing, which became incredibly useful later as more annulars were added – the positioning and shape of the arcs for each annular could be calculated mathematically using these variables (see the source code for how this was done).

var annularXOffset  = 100; // how much to shift the annulars horizontally from centre
var annularYOffset  = 0; // how much to shift the annulars vertically from centre
var annularSpacing  = 26; // space between different annulars
var annularWidth    = 22; // width of each annular
var annularMargin   = 70; // margin between annulars and canvas
var padAngle        = 0.027; // amount that each segment of an annular is padded
var cornerRadius    = 4; // amount that the sectors are rounded

This allowed me to ‘play around’ with the size and shape of the annulars until I got something that was ‘about right’.

Annular representation of data - step 4
Annular spacing overlapped


Annular representation of data - step 3
Annular widths and spacing looking better

At this stage I also experimented with the padAngle of the annular arcs (also defined as a variable for easy tweaking), and with the stroke weight and colour, which was defined in CSS. Again, I took inspiration from GRLC’s corporate branding.

Placing dataset labels on the arcs

Now that I had the basic shape of the visualisation, the next challenge was to add dataset labels. This was again a major blocking point, and it took me a lot of tinkering to finally realise that the dataset labels would need to be svg text, sitting on paths created from separate arcs than that rendered by the d3.pie function. Without separate paths, the text wrapped around each arc segment in the annular – shown below. So, for each dataset, I created a new arc and path for the dataset label to be rendered on, and then appended a text element to the path. I’d never used this technique in svg before and it was an interesting learning experience.

Annular representation of data - step 6
Text on arcs is a dark art

Having sketched out a general approach again helped here, as with the addition of a few extra variables I was able to easily create new arcs for the dataset text to sit on. A few more variables to control the positioning of the dataset labels, and voila!

Annular representation of data - step 7
Dataset labels looking good

Adding a legend

The next challenge was to add a legend to the diagram, mostly because I’d decided that the infographic would be too busy with Library labels on each data point. This again took a bit of working through, because while d3.js has a d3.legend function for constructing legends, it’s only intended for data plotted horizontally or vertically, not 7 data sets plotted on consecutive annulars. This tutorial from Zero Viscosity and this one from Competa helped me understand that a legend is really just a group of related rectangles.

var legend = LegendLayer.selectAll("g")
    .attr('x', legendPlacementX)
    .attr('y', legendPlacementY)
    .attr('class', 'legend')
    .attr('transform', function(d, i) {
        return 'translate(' + (legendPlacementX + legendWidth) + ',' + (legendPlacementY + (i * legendHeight)) + ')';

    .attr('width', legendWidth)
    .attr('height', legendHeight)
    .attr('class', 'legendRect')
    .style('fill', color)
    .style('stroke', legendStrokeColor);

    .attr('x', legendWidth + legendXSpacing)
    .attr('y', legendHeight - legendYSpacing)
    .attr('class', 'legendText')
    .text(function(d) { return d; });
Annular representation of data - step 8
The legend isn’t positioned correctly

Again, the positioning took a little work, but eventually I got the legend positioned well.

Annular representation of data - step 9
The legend is finally positioned well

Responsive design and data visualisation with d3.js

One of the other key challenges with this project was attempting to have a reasonably responsive design. This appears to be incredibly hard to do with d3.js. I experimented with a number of settings to aim for a more responsive layout. Originally, the narrative text was positioned in a sidebar to the right of the image, but at different screen resolutions the CSS float rendered awkwardly, so I decided to use a one column layout instead, and this worked much better at different resolutions.

Next, I experimented with using the Javascript values innerWidth and innerHeight to help set the width and height of the svg element, and also dynamically positioned the legend. This gave a much better, while not perfect, rendering at different resolutions. It’s still a little hinkey, particularly at smaller resolutions, but is still an incremental improvement.

Thinking this through more deeply, although SVG and d3.js in general are vector-based, and therefore lend themselves well to responsive design to begin with, there are a number of elements which don’t scale well at different resolutions – such as text sizes. Unless all these elements were to be made dynamic, and likely conditional on viewport and orientation, then it’s going to be challenging indeed to produce a visualisation that’s fully responsive.

Adding tooltips

While I was reasonably pleased with the progress on the project, I felt that the visualisation needed an interactive element. I considered using some sort of arc tween to show movement between data sets, but given that historical data (say for previous years) wasn’t available, this didn’t seem to be an appropriate choice.

After getting very frustrated with the lack of built in tooltips in d3.js itself, I happened upon the d3.tip library. This was a beautifully written addition to d3.js, and although its original intent was for horizontal and vertical chart elements, it worked passably on annular segments.

Annular representation of data - step 10
Adding tooltips

Drawbacks in using d3.tip for circular imagery

One downside I found in using this library was the way in which it considers the positioning of the tooltip – this has some unpredictable, and visually unpleasant results when data is being represented in circular format. In particular, the way that d3.tip calculates the ‘centre’ of the object that it is applied to does not translate well to arc and circular shapes. For instance, look at how the d3.tip is applied to arc segments that are large and have only small amounts of curvature – such as the Geelong arc segment for ‘Members’. I’ve had a bit of a think about how to solve this problem, and the solution involves a more optimal approach to calculating the the ‘centre’ point of an arc segment.

This is beyond what I’m capable of with d3.js, but wanted to call this out as a future enhancement and exploration.

Adding percentage values to the tooltip with d3.nest and d3.sum

The next key challenge was to include the percentage figure, as well as Library and data value in the d3.tip. This was significantly more challenging than I had anticipated, and meant learning up on d3.nest and d3.sum functions. These tutorials from Phoebe Bright, and LearnJS were helpful, and Zan Armstrong’s tutorial on d3.format helped me get the precision formatting correct. After much experimentation, it turned out that summing the values of each dataset (in order to calculate percentage) was but a mere three lines of Javascript:

var CollectionItemCount = d3.nest()
    .rollup(function (v) { return d3.sum(v, function(d) { return d.Items})})

Concluding remarks

Data visualisation is much more challenging than I thought it would be, and the learning curve for d3.js is steep – but it’s worth it. This exercise drew on a range of technical skills, including circular trigonometry, HTML and knowledge of the DOM, CSS and Javascript, and above all the ability to ‘break a problem down’ and look at it from multiple angles (no pun intended).














The Light Clock

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My Light Clock arrived on Friday, and the weekend was a great opportunity to set it up and learn more about how it worked.

I’d backed this project for two key reasons;

  • The project was run by an Australian hardware and software engineer – Chris Carter – who was recommended by colleagues in the opensource community. I’m passionate about opensource development, and I wanted to help back an Australian project, particularly given the success of LIFX.
  • The project was based on open hardware and open software. The base board for The Light Clock appears to be the arduino-compatible ESP8266 which is fast becoming the go-to board for open hardware developers. The lighting is based on AdaFruit’s neopixel range.

The box was very plain and simple, and the device itself was packed with polystyrene peanuts and bubble wrap – very secure nonetheless. The Australian adaptor was included in the box, however the lead on the device was only about 1.5m long. The Light Clock sticker on the back of the device was a nice touch, however I would have liked a Light Clock sticker separate in the box for say laptop stickering. Being one of the first 200 people to receive a Light Clock device, a ‘Kickstarter Edition’ engraving or similar would have been a welcomed addition, but understandably not part of minimum viable shippable product.

First steps with #thelightclock, a @kickstarter project I backed.

A photo posted by @kathyreid_id_au on

The short lead presented the first design and installation challenge; ostensibly this device is aimed at replacing existing analogue clocks that are wall-mounted. However, it’s rare that someone would have a general power outlet (GPO) high up on their wall, necessitating a fairly long lead run to a ground-level GPO. This may not be the case in say corporate offices, which may already have networked clocks in place, or existing infrastructure for digital signage.

Connecting to the network

The next challenge was connecting to the Light Clock, and getting it on to my home wi-fi network, so that it could use NTP to keep in sync. The Light Clock correctly appeared as an advertised SSID in my Network Manager, however every attempted connection to this SSID failed. Rather than spend the time diagnosing it, I used my Nexus 5X mobile phone, running stock Android, to connect to The Light Clock SSID. This was successful on the first attempt, and I was able to join The Light Clock to my home wifi network. As expected, The Light Clock could not see my 5GHz SSID, and could only see my 2.4GHz SSID. This appears to be pretty normal for most IoT devices at the moment, but I suspect we’ll see more support for the 5GHz frequency over time. The service that joined The Light Clock wasn’t responsively designed, so it was a bit tricky on a mobile device.

Once I got the device on the network, I then went back to try and diagnose why I couldn’t connect to The Light Clock SSID via Ubuntu, and found something very interesting. The MAC address picked up by the router, shown in the image below, was;


however, the MAC address picked up in dmesg (the Ubuntu Network Manager log) was


So, I think there may be an issue with the MAC address it’s broadcasting, or how my machine was picking up the MAC address. Here’s a link to the dmesg logs in case anyone is curious. For the record, I’m using an Atheros network card in my ASUS N76. It’s otherwise generally pretty reliable.

How The Light Clock appears as a device on the router
How The Light Clock appears as a device on the router

Configuring The Light Clock

Configuring The Light Clock proved much easier than getting the device on the network. You simply connect to a web interface to the device over your WiFi network and adjust the settings.

Another observation was that clear setup instructions were at

/setup is becoming the default setup URL for devices such as this

The Light Clock settings screen
The Light Clock settings screen

Experimenting with colours yielded some interesting conclusions. The colour settings tended to work best when both colours – the hours colour and the minutes colour – were heavily saturated and bright. Neon type colours – bright pinks, yellows, blues and greens – tended to work best in terms of contrast between hours and minutes. For someone whose house is pretty much all neutral shades – stones, earthy colours – finding a colour palette that was both clearly readable but resonant with the rest of the interior design was very challenging, and I couldn’t settle on a palette that met both requirements.

The blending option when set high tended to make the time much more difficult to read, and I settled on the lowest blending setting. The other feature that would be useful here would be the ability to adjust the brightness of the hours colour setting and minutes colour setting independently, so for instance you could have a very bright hours setting and a very dull minutes setting. I’m not sure if this is possible with the Neopixel hardware though. I did have a look at the source code to see if it was an easy pull request to do, but I couldn’t figure out how the brightness value is added to the pixel colours.

The settings also had three slots to save different colour schemes, which is a useful UX addition, however I would have liked to have seen more slots. In experimenting with the hour markers, I found that no hour markers at all actually made the time more readable, which was counter-intuitive.

With a little tweaking, I think this device could be integrated into other design projects, such as on canvas or with something like LilyTwinkle.

Integration with other IoT devices

One of the key drawbacks of The Light Clock is that it doesn’t appear to have any integration with other IoT devices, such as LIFX, Hue, Nest and so on. There are a number of use cases I can see for The Light Clock to have a lot of additional value if integrated such as;

  • Using The Light Clock as a visual indicator of notifications, phone ringing and alerts
  • Synchronising The Light clock as a wake-up device. Currently I use LIFX to slowly turn on my bedroom light in the morning, and I’d like The Light Clock to be synchronised with this, particularly given that it tends to work best with neon colours.
  • Integrating Light Clock control in to other apps – such as LIFX. I’m really glad that I don’t have to install yet another mobile application to control The Light Clock – because the IoT app market is already so fragmented.

I was also half expecting some sort of documented API for The Light Clock so that I could experiment with some integration myself, and although the source code is available, the device itself doesn’t appear to have a documented API or web service. From what I can tell, the settings page basically takes a bunch of GET variables and writes them to the board, so even knowing the range of GET vars would help to be able to integrate The Light Clock with other devices.

The verdict

This is a great product for people passionate about open hardware, and who like to tinker, but it’s not yet mature enough for a mainstream product. With some small design tweaks and attention to detail in the codebase, it would be a strong standalone product, however it’s key value lies in integrating with other IoT devices to provide meaningful and valuable interactions.

I’m not sure what I’ll do with my Light Clock – I don’t have a wall mounted GPO or GPO in range where I could mount one, unless I find a longer-lead adaptor.

List of feedback for next iteration of this product

  • Include an adaptor that has a long lead to cater for the use case where someone doesn’t have a wall-mounted GPO available, or allow this to be selected during the purchase process.
  • Alternatively, the product could be redesigned to run on batteries (wasteful) or better, power over ethernet – but again the same design limitation remains – just as people are unlikely to have a wall mounted GPO available, they’re even less likely to have a wall mounted RJ45 ethernet port available. I suspect this will change as more and more people have networked devices on their wall though, so I don’t see it as a major limitation.
    Note to self: I need to include wall-mounted GPOs and RJ45 sockets in my home renovation master plan
  • Chris Carter’s The Light Clock source code is available on GitHub, but isn’t in its own project. There also aren’t any license files for the different repositories, so I’m not sure if I’m allowed to fork it or issue pull requests.
  • In the settings, you manually have to set whether it’s daylight savings time or not. Given that it uses NTP for keeping network time, I would have thought it would be possible to get it to automatically accommodate daylight savings time. Could be wrong here, NTP may not store that data, or it may be difficult to pick up the geolocation from the home wifi network.
  • Have separate brightness settings for minutes and hours
  • The web interface for adjusting The Light Clock settings would benefit from being responsively designed
  • Can haz API plzkthx 😀


Update: trying to mount it to the wall

So, I gave mounting it to the wall a go. This was a nightmare. The two circular openings to hang The Light Clock with are flush to the back of the clock, meaning that I couldn’t mount it with cuphooks  as the hooks were too curved to snag into the openings. I also tried with the Command re-usable big hooks, and tried to assemble them so I stuck them in the openings first, then tried to stick the entire lot to the wall, with no success. Definitely frustrating. Even if I had got it to mount on the wall, I would have still had a cord trailing down the wall, and the 1.5m power cord is still insufficient to reach the GPO.

Was anyone else able to mount this successfully? How did you do it?

Learning Bitcoin and the blockchain with the bitcoin computer

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Digital currencies have been gaining traction for some time now, and although I had a broad sense of what they did and how they could be used, I hadn’t had an opportunity to utilise them in a real world setting. So, I set some personal learning goals and set about achieving them:

  • To learn the terminology associated with digital currencies, in particular Bitcoin, and the blockchain, which would serve as a foundation for building my knowledge
  • To undertake some practical exercises involving the actors, methods and marketplaces for digital currency, allowing me to explore limitations, current and future applications, and understand the enterprise use cases for the blockchain.

Buying the bitcoin computer

The initial research indicated that the bitcoin computer would be a good place to start. What drew me to it was that it was backed by some big names in the industry, and its approach to a digital currency marketplace was unique; leveraging micro payments for micro transactions such as sending an SMS or an email. Based on Raspbian and running Linux also gave it bonus points 🙂

The first problem encountered was that it didn’t ship to Australia. Challenge accepted.

Having already set up an Australia Post Digital Mailbox, it was super easy to establish a ShopMate account. The experience here was seamless, and for an additional $AUD 43 my 21.c0 bitcoin computer was shipped from Portlandia to Australia. Win!

The cost of the computer was a bit steep at $USD 399, which worked out to just under $AUD 600 with the woeful exchange rate. Still, I figured this was cheaper than say a formal course on bitcoin or blockchain.

Initial steps

Unboxing, as many fellow geeks will resonate with, is a ritual, and an integral part of any large tech purchase. The didn’t disappoint. The packaging was sleek, black, minimal and beautifully put together. The Raspberry Pi-based computer was nestled comfortably in black firm styrofoam, with the power cords and accessories stashed underneath.

Inside the box was the bitcoin computer itself, power cord, and USB cable to connect the board to your computer for initial setup. The USB cable actually had four connectors, but the board has three pins. The unneeded connector (red) had been cut off, to make setup easier. This was a small detail, but indicative of the thought that had been put into the product. A USB wireless adaptor was included in the box, without which the product would have been almost unusable, so this was a great inclusion. Perhaps the only improvement suggestion here would be to use a WiFi adaptor that supports both the 2.4GHz and 5GHz ranges – my router runs two SSIDs, one on each range, and the included WiFi adaptor was only able to connect to the 2.4GHz SSID.

The only component that wasn’t initially included that I had to hunt up was a US -> ANZ power adaptor, which is forgivable considering don’t technically ship to Australia.

Behold! The first three @21 Bitcoin Computers in The Netherlands. Want to join the hackathon? Let me know!

The next step was to connect my Ubuntu 14.10 LTS-based laptop to the and run some setup software. This was excellently documented, with instructions inside the box itself, and also prominently displayed on the website. What I really liked about the setup was that there was an automatic version, and a manual version if you had more experience on a Linux CLI. There were also options for other operating systems.

I got a little bit stuck on the initial setup, and couldn’t get the script to run. Initially, I wondered whether I’d triggered an unsafe shutdown of the device, and it was trying to re-index the database, so I let it run setup overnight. This didn’t fix the issue, so I jumped on to the support Slack (about 0700hrs Australian Eastern Standard Time – so GMT +1000hrs), thinking that no one would be online. Not only was support readily available, it was helpful, polite, friendly, and assumed that technically I knew what I was doing – an excellent support experience. In the end, it was a total n00b issue – the microSD card in the computer wasn’t seated correctly!

#21co first steps with #bitcoin and #blockchain

A photo posted by @kathyreid_id_au on


Learning a bit more

Once I had run setup successfully, I was able to mine my first Satoshis (sub-units of Bitcoin currency). Because it’s now difficult to mine Bitcoin directly, due to the computational complexity, a single machine has a very low probability of successfully mining a Bitcoin block. To work around this limitation, facilitates a collective approach called buffered pooled mining. In this scenario, many computers work co-operatively to mine Bitcoin, and collectively distribute the rewards. This means that you may only receive a few thousand Satoshis per day, but it’s sufficient to learn the concepts involved and start to prototype applications and ecosystems that leverage Bitcoin and the blockchain.

The next challenge was to see if I could set up a simple application that utilised the infrastructure to provide services for micro payments of Bitcoin. Using the tutorial, it was reasonably quick and easy to do. I found all the tutorials were written in really clear, simple terms, and stepped you through the different concepts being demonstrated in a very logical way. There were a few glitches along the way, mostly to do with package management and dependencies, so having at least a basic grasp of apt and pip was very useful.

I’m not sure where I’ll go next with this hardware – perhaps a micropayment webservice or too, but even with the initial steps here I’ve got a much better understanding of how Bitcoin and blockchain concepts can be applied more broadly. I could choose to run the 21 Bitcoin computer as a full Bitcoin node, but my internet connection is so slow that it probably isn’t worth it.

Use cases for the blockchain

The foundation of digital currency – the blockchain – has implications far beyond monetary transactions. The blockchain itself models provenance – the ownership of an asset (in the case of digital currencies, monetary assets) over time. Could it be applied to the physical as well as digital world, for instance to record the change of ownership of physical assets? I’m not so sure.

Physical and digital assets have different properties that may limit the blockchain’s applicability to the physical world – for instance physical assets such as cars, houses and jewellery can both be destroyed, or reconfigured. For instance, I could take piece of clothing and burn it, thus destroying it. The blockchain – or at least the Bitcoin blockchain, cannot easily handle such a use case, and the protocol would need to be extended to do so. It also cannot handle the reconfiguration of assets. Let’s say that I have a string of pearls, with 100 pearls on the string, that was given to be my by mother. The blockchain could record the change of ownership from my mother to I, but let’s say that I cut the string of pearls in half, creating two shorter strings with 50 pearls each, and then I gift one of the 50-pearl strings to my sister. The blockchain could handle this monetarily – splitting one value into two values, each distributed to separate owners, but it could not handle this physically – but recognising that two separate assets had been created where one previously stood. Of course, it’s possible that in time extensions or additions to the blockchain would address these shortcomings – it will certainly be an interesting thread to track.

Privacy and identification in the blockchain are also of interest. The blockchain itself doesn’t identify participants in transactions, which is great for privacy, but not so great for transparency. I suspect we’ll see the rise of services such as OneName which help to identify participants. For instance, imagine if government transactions were on the blockchain – you’d want them to be transparent.

Of course the blockchain itself also represents a unique big data source. As the use of Bitcoin evolves over time, it would be an interesting exercise to observe trends or changes in the patterns of transactions – such as average value, the frequency that BTC was transferred to or from particular addresses and so on.

Another interesting application of blockchain could be in content management and for handling versioning – as essentially a content management system is a series of assets that are mutative via known transaction types. Using blockchain for content management would also help to solve some of the problems around “what did a particular asset or collection of assets look like at a point in time” – as the blockchain contains an entire historical record.

A fascinating area.