Saturday, 2 January 2010

MoSCoW Requirements

I'm not entirely sure how requirements are normally arrived at. I decided to stick to a prose style and tried to cover all the requirements I could think of.

Overview

The system is intended to be used after the analysis of a project. When the analysis is complete, the bug alerts will be displayed in an ordered fashion designed to provide the best return on investment for the time spent triaging. To provide this ordering, the user should take part in a supervised learning session to train the system on the analysed project. The learning should select examples from the analysis which will provide the most information about the project. To determine the order of bug alerts for the learning session Kremeneck et. al's Information Gain algorithm will be used. Users should be able to end the training session whenever they wish. This means that bugs which are morely to be true positives are shown first. Within the bugs likely to be true positives there should be an ordering of priority. This probability of a true positive will be determined using Kremeneck et. al's FEEDBACK-RANK algorithm. A custom priority model should be implemented to bring the bugs the user most cares about to the top of the list.

It is intended that the investment in performing a supervised learning session will provide a net gain in the efficiency of bug triaging. Because priority of a bug is included in the ordering, the system should identify the bugs most important to the user first. If the user has limited time to triage bugs, they should be able to use a "skimming the cream" approach, which should still justify Findbugs' usage. The user should be able to detect when they are encountering a large ratio of false positives, and have a high confidence that they can end the triaging session.


Learning Session
Once an analysis is complete, the user should be able to enable a learning mode. At this point the system should calculate the Information Gain for each bug report. The Information Gain algorithm should be the same as used by Kremeneck et. al. Once this value is calculated for each alert, the interface should display the alerts in order. The user should then be able to classify each alert as a true or false positive, with a priority. The system could also alert a user when the Information Gain value from the remaining alerts reaches a low enough level that it is no longer worth continuing the learning session. The system could also present a streamlined user interface for classifying the alerts, for example, by displaying all the keyboard shortcuts required to make the mouse unneccesary. The system should also persist the results of the learning session so they may be shared, triaging can be deferred and learning is an incremental part of the continuous build of a project.


Triaging Ranked Alerts
Following a learning session, the system should be able to order the alerts based on the FEEDBACK-RANK (with priority). The system could display information on the ranking (such as a gauge for each alert ala Google's PageRank). The system could also provide a streamlined interface, as described for the learning session. The system should use the feedback provided for each alert to update the ordering of the alerts. This could be done automatically, but if performance is an issue it could be at the user's request. The system could provide information on the user's progress through the ordered alerts (for example, traversing the graph of the orderered FEEDBACK-RANKs). The system could provide a separate area of the UI or use the existing UI to display the ordered bugs. Once an alert in the queue is classified, it should be removed from the interface. However, the user must be able to revisit already classified bugs (they may change their mind), therefore the system should allow displaying already classified alerts. The system should persist classifications in this mode in the same way user classifications are already persisted. The system could inform the user when they have reached a point where the remaining bug alerts are more likely to be false positives.

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