General XML Schema

A very vital component of an Ajax based application is the XML. This mark-up language tool has been tapped to ensure that the client side of the online application is as lightweight as possible.

A client side online application will usually require a higher bandwidth because it continuously streams data to the browser. But with the help of XML, the application could easily stream data on the client side.

The ability to be adaptable to other languages of XML has also increased the possibility of mash-ups in an Ajax based application. Instead of simple JavaScript, you’ll have additional programming languages to improve the application.

But XML could be subdivided into further categories. These categories aim to improve the security of the application as they increase the screening process of the data that could be integrated in the application.

Called the XML schema (take note of the lower case), this type of XML helps the Ajax based application and other programming languages increase security as it will validate the data entered against the rules set by developers.

There are many type of XML schema developers could use. But there are only three major XML schema types that developers are seriously working today.

XML Schema of W3C

Before moving forward, take note that this form of XML Schema may have the same name as the general schema but it’s different when compared to other types. The XML Schema was outlined by W3C. To avoid confusion with the general term, this type of XML schema is now known as XSD or XML Schema Definition.

The main focus of XSD is on the aftermath of validation. It will have the same features of validation but after this process, the XSD will be creating a list of data types that was accepted for developers to see.

Because of its post validation procedures, this has been under fire by many developers. Since it creates a list and opening up a lot of data types during validation, it can’t be easily secured or even understand.

Document Type Definition

A widely popular alternative to XSD, this form of XML schema has been preferred by most developers because of its simplicity. Instead of going around the rules set be developers, DTD will strictly rely on the restrictions set by developers. This gives the developers more freedom on increasing security in their application. DTD is also seen as the default validation tool for XML.

But DTD is often seen as a very limited tool for XML. On the other hand, considering the options you would have, DTD would definitely be a better option.

RELAX NG

If you do not want the complications of XSD or even the DTD (although it’s already simple); RELAX NG would be your choice of XML schema. In gist, this is a very compact type of XML schema. But its main feature is that it is commonly found with XML which means adoption is very easy. This type of XML scheme is perfect for simple applications but handles very important data.