StAX and XML Accelerators tutorial

1.                         Introduction

XML Technology is gradually becoming the standard for Data Interchange. Most organizations in the world use XML is some form or the other. XML forms the basis of many future inventions in the field of information technology.

In spite of all these very lucrative advantages, the very basis of technology is under threat due to reduced Performance aspects that solutions have to live with due to the very nature of the parsing and processing technologies.

In the world of Java, there are primarily three options that are provided to parsing of XML Structures namely DOM (Document Object Model), SAX (Simple API for XML) and STAX (Streaming API for XML).

DOM and SAX have traditionally being used for parsing XML Structures. STAX is a relatively newer member of XML Parsing technology in the Java World.

1.1.                  StAX – Pull Model

STAX is built upon the concept of Pull model in which an application queries the parser for the next parsing event, but never surrenders control to the parser during the process. Stated differently, StAX essentially turns the SAX processing model upside down. Instead of the parser controlling the application's flow, and the application reacting to parsing events, it is the application that controls the flow by pulling events from the parser.

Pull Parsing Model in StAX allows for

a)      Control over the Parsing Engine

b)     Greater Programmatic control over the XML Data Structure

c)      Reduces heavy memory footprints, which are required due to usage of DOM Parsing techniques.

d)     Simple processing model such as used with SAX

e)      Event based processing control (this is called Pipelining) on XML Documents

f)       The StAX cursor model is the most efficient way to parse XML since it provide a natural interface by which the parser can compute values lazily

g)      It is more optimized for Speed and Performance in comparison to DOM and SAX

In spite of the advent of the STAX as member of the Java Technology, still a lot of debate exists in adoption of XML Technologies, mainly due to performance overheads.

1.2.                  XML Accelerators

XML Accelerators are the newest mechanism appearing in the industry. Currently there are primarily three options available in dealing with Improving XML Performance

a)      Microprocessor based acceleration: This option takes into account the fact that faster microprocessors will process XML data faster than not so fast microprocessor.

b)     Standalone XML Accelerator Engine: This devices hook into the individual applications and reduce the XML data beings transmitted across applications. What these don’t attempt to is improve the performance of XML processing on Individual Application.

c)      PCI Hardware boards for XML Accelerators: These hardware boards actually separate XML processing from the application thereby improving performance.  Figure below gives an example of PCI based Hardware Board processing mechanism

1.3.                  Conclusion

StAX is definitely is a much better solution implementation option as compared to DOM and SAX. However in order to boost XML Performance use of XML accelerator solutions is still evolving. Meanwhile, choice of the PCI Hardware based XML Accelerators for today may good option to enhance XML processing and implement the much needed SOA solutions.