Wednesday, October 19, 2011

Client Driven Modifications

There are now three thousand entries in the database. A thousand came from a single evening's work by my niece. Another 500 came from a nephew. The remainder probably came from my daughters. A number of design changes are prompted by the data so far.

The first is a mechanism to prevent multiple errors. If a student can't solve say 20 divided by 10, nothing is gained by having them submit 10 consecutive wrong answers. It wouldn't happen in a pencil and paper test and it shouldn't happen in my Java Math Test. For the purpose of pure Rasch theory, all that matters is that one student did not know the answer to one question. So including 10 wrong answers in the database gives rise to quite a serious distortion. But from the perspective of the user, allowing only a single attempt might be confusing; or would it?

My first instinct had been to add a "cheat" or "panic" button, to get the user out of a bad loop. And the current code just leaves the item there for a second (third, fourth ...) attempt. But, after thinking about the theory, and the traditional pencil and paper test, perhaps the correct procedure is to log the wrong answer, and go straight on to the generation of the next item. In this case, something needs to be added to the messages, to remind the student what the item was, and to inform them of the correct answer.

The second is a mechanism for me to track more accurately when the Applet is being used by outsiders as opposed to family members. Getting the IP address of the visitor to a web page is pretty easy with PHP, but the question is how to store it. In the current format, the SQL query is more or less written by the time a PHP script is called, and there is no field in the database for an IP address to be stored.

The third change, requested by a school in the Philippines, is the ability to track individual students. I had deliberately left this out, because of the Australian/Western obsession with privacy.

Australian data protection legislation enshrines ten privacy principles, which begin with:

An organisation must not collect personal information unless the information is necessary for one or more of its functions or activities.

The key word here is personal. I don't need personal information, but if users elect to personalize their own transactions for their own purposes, they must deem it necessary. Furthermore, if schools are encouraged to use avatar ids, which only they can associate with real students, my data will remain impersonal to anyone except those who created it.

Another principle worth mentioning (Number 8 on the list) is:

Wherever it is lawful and practicable, individuals must have the option of not identifying themselves when entering transactions with an organisation.

So notwithstanding what tracking mechanisms certain schools elect to use for their own purposes as long as I maintain the open (and anonymous) portal, the project as a whole will comply with this principle.

Of course if schools or individuals ignore my recommendation to preserve anonymity, there are eight other principles to consider, including data quality, security, openness, access and sensitivity. I think I need to cut and paste a suitable "conditions of use" from somewhere for those who elect to track their own data.

Leaving aside these potential legal issues, if I am changing the database to enable schools to track their students, I can pop in a field for the IP address at the same. And while I'm at it, I'll modify the Applet structure to collect some data before use as well as storing data after use. In my first post on Applet/Javascript Communication, information was passed from a web page to an Applet, so I can use that model to pass the student id and IP address to the Applet as parameters. They can then be woven into SQL statements to be passed back to the host page.

In the current version, users are taken straight to the page hosting the applet. In future versions, users will go first to a PHP page, which offers the option to log in, or to remain anonymous. They will then go to the page hosting the applet, and carry with them an id parameter, which will either be a real id for those who have logged in, or an anonymous id generated from the date stamp and IP address. Technically of course, the IP address could be used to identify a user, but most ISP would only give personal information to government agencies is special circumstances. As the users of my applet are not doing anything illegal, this is not going to happen.

The fourth change, which might as well be woven into all these others, is to allow operations with decimals. The current Items table only allows operations with integers. In fact the field type is actually small int, which further restricts the fields to plus or minus 32767. This is fine for multiples of ten in the order of magnitude, but it could lead to problems with larger multiples. I think for the foreseeable future, a single precision float will be more than adequate to store decimals in the item columns, as well as larger number if required.

The question is, should the IP address be stored alongside id with every transactions. It is a bit of a Catch 22. With the current infrequent use, the start time in milliseconds should be more than adequate for unique separation of sessions, because the odds of two sessions beginning simultaneously are very low. But with the current infrequent use, space is not an issue so IP could be included without running into storage problems. And as the frequency of use increases, and the odds of two simultaneous starts increase, so space becomes more of an issue as well. I think for now, I'll shove the IP address in. After all, computer space is pretty cheap these days, so even if I hit my web host limit, I can always siphon data off and store it at home.

For the handful of schools who want unique tracking, I can add an extra table to store their user id's and any other data they want to store alongside it.

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