mx_, posts by tag: development - LiveJournal

Ima talk about how watch/clock works a little bit.  It's a very good analogy for understanding N-Tier application structure.  

A watch has one crucial component - some cool thingie, which oscillates at equal intervals (a "heart" of a watch).  In old clock, it was a pendulum, in new electronic clock, it's the light with precise frequency. No matter what little piece of crap they have oscillating, be it a tail of a dog, or the frequency of audience laughs on the Will and Grace show, doesn't matter.  What matters is for these oscillations to be of equal intervals.  So, we got our oscillator (your dorm neighbor's vibrator).  It is our source, our initial data.  Let's call our oscillator the Data Layer.

Ok, moving on.  Our next task is to somehow get the oscillations, in order to use them.  In other words, we need to access the data in the Data Layer.  It should be some sort of device, which is going to convert these oscillations into something useful, for example electronic impulses.  In our case it could be a camera pointing through the keyhole of her door as she masturbates. Let's call this accessing device the Data Access Layer.

We're at step three. We got the oscillations accessed.  However, those oscillations are very far from the Earth seconds, I'm pretty sure.  We need some smart mechanism, which can recalculate the frequency of our source oscillations into our target frequency - seconds.  In mechanical watch this is done through a set of gears, precisely organized to move the hands of the clock.  In electrical watch they use some integrated circuit, which does the job.  In our case, we could assume that it takes her exactly 47 seconds to come.  You know, whatever floats the boat.  This process transfers the data from some ambiguous initial state, to an understandable representation for us, the everyday folk.  Let's call this recalculating device the Business Layer.

Now, that the calculations are done, we're left with one last thing.  The Interface.  We need to somehow display the time to an ignorant average Joe, in his favorite am/pm i-don't-know-numbers-above-twelve representation.  In mechanical watch you mostly had to resort to the arrows ("hands") going in circles.  With electronic watch, we could display the time anyhow (be it arrows, digits on the LCD screen, or little LEDs, which tell time in binary, sold on thinkgeek.com).  For representation we use conviniently prepared information from the Business Layer, which is already calculated and makes sense to us. This, of course, is called the Interface or Implementation Layer.

The same exact idea is applied to web-programming. Only, instead of Quartz, we have the database, and Stored Procedures within it. They get raw information from the database and pass it further to the Data Access Layer. Then, instead of oscillation extractors, we have Data Adapters, which convert the raw data into Data Tables, useful within the code of the program.  Next, instead of gears, we have classes with functions making up the Business Layer.  Those classes have methods, which will adopt the DataTables to some specific cases that we expect in our application. And finally, instead of arrows, we will have HTML and CSS as our representation layer.  Except, if we go even further, we could break up the representation layer into even more tiers by introducing XML + XSLT.  But I'll tell about it later.  (Here's some diagram I found.)

The beauty of such approach is that each layer can be maintained independently, kept on different computers on the network, and even be replaced with something else.  For example MySQL database could be replaced with MSSQL, or Access, or flat file.

Oh yeah, I forgot to make an analogy of Representation Layer with our particular case.  Well, who gives a fuck about time when watching amatuer porn. Do everybody a favor, and spread it across p2p network, and newsgroups - that's your damn representation.