YWorks - products

Came across this company that calls itself a 'diagramming company'.
A list of their product offerings can be found here.

Two interesting 'free' products that are included are:
- ANT script visualizer
- Java obfuscator

Ready to go templates

Believe it or not! There is a open-source project that aims to provide ready-to-go templates for all phases of a product or an application.
Link: http://readyset.tigris.org/nonav/templates/frameset.html

Difference between CPU time and elapsed time

In Performance metrics jargon, we often come across two measurements: CPU time and total elapsed time. So whats the difference between the two?

CPU time is the time for which the CPU was busy executing the task. It does not take into account the time spent in waiting for I/O (disk IO or network IO). Since I/O operations, such as reading files from disk, are performed by the OS, these operations may involve noticeable amount of time in waiting for I/O subsystems to complete their operations. This waiting time will be included in the elapsed time, but not CPU time. Hence CPU time is usually less than the elapsed time.

But in certain cases, the CPU time may be more than the elapsed time !
When multiple threads are used on a multi-processor system or a multi-core system, more than one CPU may be used to complete a task. In this case, the CPU time may be more than the elapsed time.

Difference between different editions of VS 2008

I was looking for a official comparision between the different VS2008 editions and thankfully I found it here.

The express editions are different downloads for each language. i.e. for C#, VB.NET
So if you want to open different projects in different languages, then go for standard or professional. Then the express editions do not have visual designers for WPF and WWF.

Some of the differences between the standard edition and professional edition are that you can use the professional edition to build MS Office applications. Also the professional edition has support for Crystal reports, Unit testing etc.

More information can be found at the following links:
http://msdn2.microsoft.com/hi-in/vs2008/products/default(en-us).aspx
http://msdn2.microsoft.com/hi-in/vs2008/products/bb894671(en-us).aspx

ETag response header

HTTP 1.1 introduced a new kind of cache validator i.e. ETag.

ETags are unique identifiers that are generated by the server and changed every time the resource is updated. An ETag is a string that uniquely identifies a specific version of a component. The only format constraints are that the string be quoted.

ETag: "10c24bc-4ab-457e1c1f"

The problem with ETags is that they typically are constructed using attributes that make them unique to a specific server hosting a site. So in a typical clustered environment, if the next request for a cached resource goes to a different server, then the ETag won't match and the resource would be downloaded again.

Most modern Web servers will generate both ETag and Last-Modified validators for static content automatically; you won't have to do anything.

More info about ETag can be found at the following links:
http://developer.yahoo.com/performance/rules.html#etags
http://nerdmonkey.com/blog/archives/000098.html
http://www.web-caching.com/mnot_tutorial/how.html

The advantage of ETag over the 'last-modified-date' tag is that the fact that ETags don't require a date but will take any string. So U can compose ETag with any custom logic and source.

Parallel download in browsers

We all know that browsers make multiple requests to servers for each and every resource that is contained in the page. But what is the max number of persistent connections that the browser can make to download all elements of a page?

Well to my suprise, the W3C specification on HTTP 1.1 actually states the same.
"A single-user client SHOULD NOT maintain more than 2 connections with any server or proxy. "

What this essentially means is that broswers can download no more than two components in parallel per hostname. U always discover new things :)

YSlow for Firebug - cool cool extension

I have been a die-hard fan of the 'Firebug' add-on to Firefox. Firebug has proved to be invaluable to me for diagnosing front-end performance issues.
Now Yahoo has extended Firebug with another feature called 'YSlow' that shows good aggregate data and also recommends changes to be made in the page.

More information can be found at http://developer.yahoo.com/yslow/