Google PageRank

PageRank is an algorhytm for rating the relevance of web sites designed in 1987 by Larry Page and Sergey Brinn. It is the base of Google search engine.

Algorhytm uses strusture of hypertext links as each other "recommendations"of webpages. The rating is not computed just from number of comming links , but from ranks of recomendating sites too.

If we wanna compute PageRank R(a) of site a, we could use scheme that looks like this:

where Ba is group of all pages linking on a, and Nu is number of links going from u. Basicly every site gives its rank to pages, that it links.

Problems with PageRank computing are closed site structures, on which links goes, but doesn't go out. For example two joined sites with link from outside on one of them would during the computing acumulate and will not release anything. This creates some kind of "trap", that Page and Brin calls "sink". Becouse of this is PageRank even more difficult, becouse it stops this sinks.
If you wanna compute Google PageRank for your site, you need to use Google Toolbar. But it is still not completely exact and it works just with IE or mofo. It looks like this:



PageRank is trademark of Google, Inc. and algorythm is patented (Patent USA 6285999) by Stanford University.

For webmaster is importing just that as height is your PageRank, as big importance gives Google to it. As height is importance, as height is the page placed in search result.Of course thats not the only criterium, Google has about 100 of them. Another advantage is that GoogleBot brows the sites with bigger PageRank more often. Google actualize PageRank in cca 3moths intervals.

We must admit that this is all hust a theory and noone without the deepest employers of Google knows for what purpous exactly PageRank is.

References:
Wikipedia (en)
explanation on JakPsatWeb (cz)
Article about toolbar pagerank (cz)

The Google Desktop

Today i've installed, until now, to me unknown product from Google - Google Desktop. Wikipaedia says that first version for windows was released 3years ago, for Mac on April and last month for Linux. I decided to write about it, becouse i think it's hightly effective and not very known. The first contemplation was to integrate google-style indexing into a desktop pc, but during the time, there appeared some gadgets (a pseudo widgets) and similar stuff. I, personaly don't believe on gadgets, becouse they eats much of memmory, like themes etc. But you could set Google Desktop as simple small textbox on the panel, which after filling a keyword starts immidiately show all files and mails, containing it in the name, or content. I think it's a PC version of Apple's Spotlight, so theres no reason to put it on Mac, but PC users would (IMO) like it. I didn't test it on Linux yet, but now i sit at PC with Windows XP, 200GB disk and 256MB of RAM and the results are fantastic. While it tooked 3 and a half minute to find all clues to Windows search (yes, that awfull dog), Google Desktop brought all results in 2seconds and in another 4 it included all mails and conversations from gmail too. Wonderfull. Google could do it thanks to indexing all files to its own database. Then it loads it based on their relevance. Of course, first it must index them. On my computer tooked it about ~4hours. However it does it when a computer is not working for more than 30seconds - just like screensaver - so it doesnt slow our work much. With a technology and system that allows you to search about 6exabytes of datas in time under one second and classify them on effective relevance, there is no problem with finding something on your small, pathetic disk, even if it has a terrabyte and your case contains just 700mHz Intel..
I had a small problem, during the instalation, and have to reinstall it, but now all works perfect. Maybe someday i will test the gadgets too, but on another PC.If you don't have Mac and you have a 30GB+ HDD, i advice you, to install it, you wouldn't sorry that.

Quote from desktop.google.com:

You have lots of information on your computer. Wouldn't it be great if you could find it all when you need it? You can use Google Desktop to locate your files, emails, past IM chats, and web pages you've seen. And Google Gadgets with sidebar puts up-to-the-minute info - your email, photos, weather, news stories, etc. - right on your desktop.

When you look at a web page, read an email, or edit a file, Google Desktop indexes that item and copies the item's content into your local cache, so that you'll be able to find older versions of files and web pages.

Depending on how much data your computer contains, it could take Google Desktop a few hours to index all your existing information. Since this one-time initial indexing only happens when your computer is idle, it shouldn't slow down your work. But it might be a good idea to go to lunch or to leave your computer on overnight to let it have time to index without your work interrupting the process.