WattDepot Katas

To begin our exploration of energy-related programming, my fellow ICS classmates and I have been tasked with hacking out 6 programming exercises, or katas, that deal with WattDepot.

What is WattDepot you ask? Well, here is part of the description from the host site:

"WattDepot is an open source, RESTful web service that collects electricity data (such as current power utilization or cumulative power utilization) from meters and stores it in a database. The data can then be retrieved by other tools for visualization and analysis. It is designed to provide infrastructure for experimentation and development of "Smart Grid" applications."

So as you can see, WattDepot is a useful tool for viewing energy consumption data. Here are the 6 katas we were required to do in order to become more familiar with the WattDepot library:

Kata 1: SourceListing

Implement a class called SourceListing, whose main() method accepts one argument (the URL of the WattDepot server) and which writes out the URL argument and a list of all sources defined on that server and their descriptions, sorted in alphabetical order by source name.

I finished this kata during class. It took me about twenty minutes and was pretty straightforward.

Kata 2: SourceLatency

Implement a class called SourceLatency, whose main() method accepts one argument (the URL of the WattDepot server) and which writes out the URL argument and a list of all sources defined on that server and the number of seconds since data was received for that source, sorted in ascending order by this latency value. If no data has every been received for that source, indicate that.

This kata was also straightforward. It took me a half an hour or so.

Kata 3: SourceHierarchy

Implement a class called SourceHierarchy, whose main() method accepts one argument (the URL of the WattDepot server) and which writes out the URL argument and a hierarchical list of all sources defined on that server. The hierarchy represents the source and subsource relationship between sources.

This was the only kata I didn't complete. I couldn't figure out how to get the subsource data that I needed in order to print the hierarchy the way I wanted.

Kata 4: EnergyYesterday

Implement a class called EnergyYesterday, whose main() method accepts one argument (the URL of the WattDepot server) and which writes out the URL argument and a list of all sources defined on that server and the amount of energy in watt-hours consumed by that source during the previous day, sorted in ascending order by watt-hours of consumption. If no energy has every been consumed by that source, indicate zero.

Katas 4, 5 and 6 together took me about three hours altogether. They were pretty challenging because this was the first time I dealt with timestamps or dates in Java, and I found them to be very non-trivial.

Kata 5: HighestRecordedPowerYesterday

Implement a class called HighestRecordedPowerYesterday, whose main() method accepts one argument (the URL of the WattDepot server) and which writes out the URL argument and a list of all sources defined on that server and the highest recorded power associated with that source during the previous day, sorted in ascending order by watts. Also indicate the time when that power value was observed. If no power data is associated with that source, indicate that.

Kata 6: MondayAverageEnergy

Implement a class called MondayAverageEnergy, whose main() method accepts one argument (the URL of the WattDepot server) and which writes out the URL argument and a list of all sources defined on that server and the average energy consumed by that source during the previous two Mondays, sorted in ascending order by watt-hours.

This kata was hard because you had to figure out how to determine the day of the week in order to find the average energy for a Monday--another non-trivial task. This kata took me about an hour.

From these katas I learned that energy data manipulation can be really useful. I think its important that the software analyze the data and create output that is easy to read and understand. That way it can be utilized fully by other professionals and not just other programmers.