Standards for Technology in Automotive Retail
This section addresses the requirements for the selection and implementation of compression standards within STAR. Two alternative compression standards are discussed, a convention around payload compression and the mechanism of doing http compression.
The goal of compression is reduce the size of the large documents so that transfer across the Internet can be expedited. There is a cost to compress and decompress a document, but with modern processing speed it may be advantageous to spend the processing resources to gain network efficiency.
Reduction of Size
STAR BODs are textual XML documents that can be reduced in size by compression, which translates the inefficient human readable format of the documents to a smaller binary format. The amount of compression is dependent on the variety and complexity of the actual text.
Not all messages need to be compressed. Implementing compression/decompression on smaller size would be counterproductive and prove to be an overhead on the Sender/Receiver systems, and result in increasing response time. A common observation about BODs is that although most will not be greater then 1MB, the small percentage that is will likely be significantly larger then 1MB.
Since small BODs may not yield much benefit in compression, it is not recommended that small BODs be compressed. Larger BODs, however, can yield great benefits and it is recommended that BODs larger then 1MB should be compressed using the gzip compression scheme. This may vary based on the quality and speed of the Internet connection at the Sender/Receiver. Given the compression point of 1MB, it is estimated that a large percentage of the BODs will not require compression.
Bandwidth between business partners
Most business partners collaborating in a STAR BOD exchange would have some level of broad band set up between them. Adding compression to the data exchanged would reduce the bandwidth required for the exchange and allow for greater utilization of the available bandwidth between partners.
Increased processing time
While it is true that compression results in reduced data size and bandwidth usage it can also result increased resources consumption and processing time on both the server as well as client. This was also shown by the W3C Study. Only where network bandwidth is constrained and processing resources are relatively cheap does the cost of additional processing time justify compression.
One of the benefits of XML is that the self-describing, textual data format can be read and understood by humans without the aid of an application. While there is no requirement for human access to the STAR BODs, compressed BODs cannot be read by humans without decompression.