by JOANNA GADEL

A fantastic pace has been noticed in the web sector. As a result, various definite standards and techniques are emerging. Every time there is an improvement, the web site design and applications grow complex, and there is a subsequent impact in the common web programming too. Several web programmers (Like: http://www.webprogrammers.com.au/) face this problem while making a website. Web programming requires expertise on many different levels. Skills in user interface design, human machine interaction, information design, scripting, code library development, database design and database queries are some of the important facets that are supposed to be had in a smart database programmer. In many or all of these levels a web programmer can face problems, and any web pattern needs to have explained the design considerations across any or all of these levels.

As such we need to be able to find a programmer who is aware of the problems area and can implement the required solutions. The programmer jobs include the solution of the problems originated in the day to day web programming. But first we must know the places where the problems usually occur.

The Problems Area

Form processing:

Form processing is the first step to record the problem of getting and verifying input from a user. It is the main part of all web applications, though there are many different approaches for solving this problem available to the web developer.

The basic method remains the same other than the actual content being entered. All forms should:

• Show an empty form to the user • Confirm the data entered to be valid and depict an error if it is incorrect • Perform the required action by the use of the data

Using either a single or multiple page design forms can be implemented. A self-referring script is needed for the single page technique, while the user can enter, confirm and submit the data through multi-page forms.

Navigational Structure:

A consistent look and feel is established by a clean, structured navigation and information design. Users can easily find their location in the sites through a proper navigation system.

There are at most three kinds of navigational structures:

• Single level navigation carries a list of top level areas. • The user can then drill down through the different hierarchical parts that the multi-level navigation has created, and they can find their desired content. Generally the hierarchy is two level deep to keep the display simple.

• Third navigational structure is the dynamic multi-level navigation that uses a hierarchy. Here the user after selecting the parent can be able to see the next level of navigation.

Database Operations

Accessing database is a fundamental problem for web developers. It is a common problem for the While entering the data into the database and editing entries through specific functions or an abstracted database wrapper, most of the times the data is found to be erroneous; this makes it a good candidate for pattern. Nearly all the programmers including php programmer (http://www.getaprogrammer.com.au/), java programmer, sql programmer and asp .net programmer make this phase as an essential part for a smooth running of any database design. They make a user interface design to clear the process.

At a higher-level many objects or items, the data used is captured by a row in the database. Here exists a common problem for the web programmers creating a set of useful functions and information based on these items.

Authentication Problems

The authentication phase needs to be revised properly with the different levels of a cheap programming. Several familiar mistakes have been there in these levels, and we are to solve them without any delay.

• The web programmers do nothing as to record or track any request to authentication in the None Level. • In the Session Level the web programmers used to track this anonymous person by the current visit only. • Another problem is there while tracking the anonymous person across numerous sessions in the web site in the Visitor Mode. • We must authenticate the person when we finally have the User with the relevant information.

These levels should be thoroughly checked up and similar other implementations should be necessitated if need be. The above levels should be considered together while in case of authentication.

Error Handling

It is a great challenge to build graceful degradation into a website. It is a vital job to hire programmers who can catch the errors before they confuse the users. By logging and notifying the errors a professional coder can prevent these errors to happen again.

Keeping the site alive even if components are off-line, the database programmers can handle any error problem by serving the database requests in the backed-up database that is read-only also.

E-commerce Problem

Using form and authentication any problem in the E-commerce can be easily solved if it is detected earlier. Only, a particular pattern independent on a particular implementation of forms or authentication is to be built. But first an interaction is to be done with the user and backend processing of the data.

[tags]programming, software, e-commerce, authentication form, processing, data, web programmers, freelance programmers, database operations[/tags]

by PETER VAN HOVE

Because of the different standards for rewritable optical media, in particular CD-RW, DVD-RW and DVD+RW, the state of the media after a quick erase is different. This state determines if it’s still possible or not to recover data with any data recovery software tool for that matter. There is some complexity involved and you may need to read this article twice Mainly because of the different exceptions and the role of the software vs. hardware.

First maybe the difference between a full erase and a quick erase on drive level:

I’m intentionally mentioning drive level because in most cases it’s the drive that executes a blank command sent by the software. So for the software it’s more or less a “hit and run” command. Send it down and walk away or poll the drive till ready.

When a full erase command is issued on re-writable optical media then the complete surface of the disc is over-written with a neutral pattern (all zeroes or all 0xAA or something like that). The result is that all data that was once present is now gone forever. There are no magical tricks to ever find the data back, the old content has been wiped completely, not even in a high end laboratory with geniuses at work would it be possible to recover the data. Additionally, the disc’s structures on the inside rings, which all drives use to determine the layout of the media , have been updated to resemble empty media. All references to tracks and session that were once there are now gone.

A quick erase is meant to be quick (duh …) and therefore the disc’s main data area is left unaffected, or at least mainly unaffected. All (or most) data remains present on the disc. What changes is the disc’s structures again, on the inside rings of the media. All references to tracks and session are deleted and the media is left in a state which seems like empty media for a CD/DVD writer (in most cases … read further).

So if the bulk of the data is still there after a quick erase … what’s the problem then you ask ? Well, the biggest problem exists for CD-RW and DVD-RW (DVD dash / minus RW).

As I explained before, during a quick erase on drive level the disc’s structures are changed so that a drive sees the disc as blank media again afterwards. And that is the big problem, an empty disc – as far as the drive is concerned – is an empty disc and the drive will not allow to read anywhere on the disc. All read commands fail immediately with drive generated errors. The drive doesn’t even try reading on the requested locations. At this point the drive is the limiting factor, there is no way to circumvent this as it’s not possible to tell the drive there is different media inside than what the drive sees for itself (*).

The only way (*) around this problem is to send the disc to a (possibly expensive) recovery lab that may have the right equipment to deal with it. As this is a by hardware limited problem, some labs have custom made hardware to deal with this specific problem.

(*) If I notice there is more interest in this then I will dedicate another article to this problem, in particular how a handy person with too much free time could try a few things.

There is one big exception for DVD-RW (not CD-RW) if the erase software works in the spirit of the DVD+RW standard. Meaning that the software doesn’t issue a “quick erase” command but instead does the erasing by itself, like it would on DVD+RW. Read further to understand.

The big exception to all the above is DVD+RW (DVD plus RW). The designers of the format were clever enough to decide that there shouldn’t be an erase function for this format at all. After all a full erase only adds to the so called DOW (Disc Over-Write) and thus reduces the quality of the media. If a full erase is truly required by the user then the application software can still simply write a neutral pattern over the complete surface of the disc with the same effect. And as a DVD+RW can have only one track in one session, changing the inner circle structures is not needed either. If there is a track already … well then there is a track already .. why change that ? If one wants to write new content then the old data can simply be overwritten. Of course this also positively influences background format and other features I won’t go in to now. In other words there is no erase command that an application can send.

If a user wants to quick erase a DVD+RW then the application software must be clever enough to simply write some neutral data over file-system structures (e.g. ISO9660 and UDF etc). And in fact that’s what most applications do when they quick erase a DVD+RW.

The consequence is that for a DVD drive there still is a track after a quick erase, so this is not blank media, and if there is a track with a length then, data recovery software can send read commands and get data back. And a scan for missing data can yield to positive results.

Same as with DVD-RW there is a big exception. The reason is that in the beginning not all drive manufacturers understood the philosophy and spirit of the well thought out “no erase command” principle. So what they did was make sure that a format command basically does what an erase command did and then they informed all software vendors, which were obviously confused, that they should send a format command instead of a blank command. Wrong …

To the best of my knowledge most drive vendors today have adopted the “no erase” +RW philosophy properly and recently developed drives don’t erase anymore, even not when a format command is sent. The same goes for the software vendors, they too saw the light. However … it’s hard to change the world and exceptions still exist out there.

So when people ask, “I have a quick erased DVD+RW or DVD-RW … can it still be recovered”, it’s difficult to give a definitive answer because it depends so much on the type and make and even firmware revision of the writer, in combination with the erase software and version of that software.

From experience, quick erased DVD+RW media, erased with a current drive and current software is very often recoverable. Chances for success degrade significantly for DVD-RW, because many applications simply send an erase command (or format command) to the drive. Quick erased CD-RW is only recoverable in the lab or with special tricks that are hard to explain here.

Hope this made sense to you …

Terminology: “Erase” and “Blank” are basically the same, software mostly uses the term “Erase” whereas official specifications and standards use the term “Blank”, as in Full Blank or Quick Blank.

Interesting links from wikipedia explaining the different formats: http://en.wikipedia.org/wiki/Compact_disk_erasable http://en.wikipedia.org/wiki/DVD-RW http://en.wikipedia.org/wiki/DVD_plus_RW http://en.wikipedia.org/wiki/DVD-RAM

Copyright © 2007, www.isobuster.com all rights reserved. This article was written by Peter Van Hove, CEO at Smart Projects. Smart Projects is an experienced company with high focus on CD and DVD technology, highly involved in CD / DVD / BD and HD DVD Data recovery with IsoBuster as one of its leading applications.

[tags]recover erased cd, recover erased cd-rw, recover erased dvd-rw, erase software, firmware, data recovery[/tags]