XML Data Compression XML is a popular meta-language that facilitates the interchange and access of data. However, XML's verbose nature tends to increase the size of a data file by as much as ten-fold.       In this seminar, we give a brief introduction to data compression followed by a review of various compression strategies designed specifically for XML data. We then present two novel XML compression techniques, AXECHOP and TREECHOP.        AXECHOP uses a grammar-based approach that exploits the significant structural redundancies within XML documents, while TREECHOP supports querying of compressed XML data without requiring prior decompression.         We compare these two techniques to other XML compression schemes with respect to compression ratio and compression time, and describe our future research.