A compressor for effective archiving, retrieval, and updating of XML documents

Abstract

Like HTML, many XML documents are resident on native file systems. Since XML data is irregular and verbose, the disk space and the network bandwidth are wasted. To overcome the verbosity problem, the research on compressors for XML data has been conducted. Some XML compressors do not support querying compressed data, while other XML compressors which support querying compressed data blindly encode tags and data values using predefined encoding methods. Existing XML compressors do not provide the facility for updates on compressed XML data.In this paper, we propose XPRESS, an XML compressor which supports direct updates and efficient evaluations of queries on compressed XML data. XPRESS adopts a novel encoding method, called reverse arithmetic encoding, which is intended for encoding label paths of XML data, and applies diverse encoding methods depending on the types of data values. Experimental results with real-life data sets show that XPRESS achieves significant improvements on query performance for compressed XML data and reasonable compression ratios. On the average, the query performance of XPRESS is 2.13 times better than that of an existing XML compressor and the compression ratio of XPRESS is about 71%. Additionally, we demonstrate the efficiency of the updates performed directly on compressed XML data.

A Framework for Query Processing over Compressed Knowledge Bases

“…COX exploits two different solutions to encode data structures and data, in a two-step compression process. For data structures (XML tags and attributes), a Reverse Arithmetic Encoding (RAE) [6] variant is used. For attribute values, a dictionary maps the most frequent strings to 1-byte codes.…”

“…The interval [1.0, d) is reserved to encode closing tags. Since every possible value is strictly between 1.0 and 2.0, the first byte will always be 01111111 2 in 32-bit floating point representation, so it can be truncated without loss of information [6]. After the first step a tag header is written at the beginning of the output file.…”

“…XGrind [8] can perform (i) exact-match and prefix-match queries directly on compressed values and (ii) range and partial-match queries on values decompressed on-the-fly. XPress [6] exploits RAE to improve the path-based queries. XPress query engine transforms a label path expression into a sequence of intervals.…”

RFID-Enhanced Ubiquitous Knowledge Bases: Framework and Approach

“…XPRESS (Min et al 2006) adopts reverse arithmetic encoding, a semi-adaptive algorithm. Furthermore, a type inference module detects data types of XML attribute values and a specialized encoding method is applied for each type (numbers, dates and so on).…”

“…Recent research has been increasingly focused on compression schemes for XML documents allowing to directly query encoded annotations (Min et al 2006), which would eliminate the need for decompression before query evaluation. To this aim, we designed an approach for compression of XML-based semantic annotations able to support queries directly on compressed data ).…”