October 07, 2006

"Software as a floor mosaic" metaphor

Here is a "software as a floor mosaic" metaphor: let's say we need to inlay a floor mosaic. We have a sketch or may be even a highly detailed plan of how the thing has to look like, and even the vision of it and clear and perfect, something like this:

We also have at our disposal assorted pieces of stone, ceramic patches, coloured sand and all the tools we might need. But no matter what tools do we have, it takes experience and above that a lot of time to make such a mosaic. Yes, experience helps but we still need to take each piece, adjust it, finish it and put it in place. Sometimes the piece will crack in our hands and we have to start over. Sometimes, a piece will be very different from what's needed in that particular spot and require much more work than another.

But then there is time pressure - the worst of all curses. Pressed with time we have the following alternative: to make it faster, we might take bigger stones and throw them in quickly yielding something like this:

And it may even sort of look similar, but I just can't force myself to see the plan in the implementation. Aesthetically, at least, it's obvious that mosaic laid out in this fashion is no match to the envisioned one. But how did our big stone practice made it break ?

In other words, what can we say about big stone mosaics ?


Bigger stones are by definition fewer, so we have to invest less in learning. The less stones we have to learn how to deal with, the more confidence we have in that we know how to handle them properly.

There is less variance between big stones, consequently there is no choice as to which stone pick for this or that spot - one less burdening decision to make.

Takes fewer pieces to lay the mosaic out. And it saves time, this is precisely the reason we choose this way.

The less pieces, the less interaction between pieces (although I must admit, this is really more a software insight).


UGLY. There are situations in which big stones fit in precisely, but those are exceptions, rather than rules. If we are up to a piece of art, not to the standard kitchen tile. This is the aesthetics-breaking reason. This is why the first one is amazing and the second one is not even satisfactory.

Along the same lines of aesthetics and taste goes this - if someone is always doing big stones, how could she tell what's beautiful and what's not ? It's still a mosaic, isn't it ?

Bigger stones obviously not always fit and we have no control over it. If we want control after all, we need to apply much more work compared to what would have needed if we were combining smaller ones from the start (that's exactly the reason why mosaic exists - we take small patches and combine them in a such a way that the whole thing looks beautiful from some distance, and don't spend forever cutting).

A mosaic built of bigger stones is less reliable (alhtough again, it's more of a software insight). We may be confident, but there is no way we can tell a crack inside a big stone, and if it happens to exist, we have no control.

And so, what's the average stone size modern software mosaics are being built of, what do you think ?

October 03, 2006

Security and usability of a real-life elevator

Security problems often appear from unforeseen interactions between different system parts. Likewise it happens when new features are added or existing ones are modified. Here is another example of that.

The office where I work occupies a five-storey building. All entrances to any level were initially equipped with card locks, and so to enter or to go from one level to another you had to have your card with you. This brought a certain amount of security, in terms of authentication and audit.

The problem was, there was initially no elevator, only stairs to access the levels. As time went on, convenience considerations prevailed and so an elevator has been installed. As such thing hasn't been predicted in the first place, the elevator shaft now couldn't be locked with card locks, simply because there is no doors on the elevator compartments, and such doors can't be installed (easily, or at all).

What happened is that security has been breached - once you have access to one level, you could take an elevator to any other without a card. This effectively defeated the entire system.

Anyhow, this is not the end of the story yet although the rest of it adds nothing from the security perspective. It's just that the elevator seems to attract user interaction problems as well.

And so one of the levels is also undergoing heavy repairs. You can enter it with or without a card now, but it's a mess therefore noone is supposed to. But the feature of entering any level without a card (in a form of elevator) is already there. Now, what's been done to prevent unaware people from using it in the wrong way, i.e. going to the second floor ?

The elevator button panel has been patched (literally, with a piece of paper and tape) so that you couldn't go to level two at all.

Now every day I come to work, this patched button reminds me of how difficult and unpredictable security and usability really is where it meets real life uses.