XML Data Stores: Emerging Practices

X ML's wide adoption in both academia and industry has revealed a controversial fact. From one perspective, XML is characterized by interoperability, ease of use, and extensibility; from another, it creates difficulties when integrated into existing systems (such as typical database applications and database management systems). One result of this conflict is the arrival of native XML data stores, which involve XML at the internal architecture level. XML is a hierarchical language, based on tags that imply parent–child relationships. In contrast , rather than using trees as basic storage elements , most DBMSs rely on tables (relational DBMSs), objects and class hierarchies (object-oriented DBMSs), or tables and objects (object-rela-tional DBMSs). Researchers proposed native XML systems to address a specific problem: when relying on a standard DBMS, the system must factorize XML documents before it can store them in its data structures. This typically entails many format mappings and interchanges between XML's hierarchical structure and the DBMS's structures, which thus requires a high number of joins to reconstruct the XML document structure during query execution. Native XML data stores define a logical model to guide the storage of XML documents 1 — similar to the way a table guides storage in a relational DBMS — and thus free the data store from DBMS restrictions. Native XML data stores have three key benefits: 2 • Scalability. Because native XML tools are based on an XML internal format, they can more easily scale to meet either client-or server-side requirements. • Data-access speed. Native XML tools don't require overhead time for mappings, interchanges , and joins between XML and other internal structures (such as tables). • Reliability. Converting to and from XML can result in mismatches between the original XML structure hierarchy and the resulting table. Native tools avoid this problem in that they use XML for the internal document representation. Here, we survey emerging native XML storage approaches and identify and highlight popular implementations tailored to XML's " nature " and syntax. By understanding the storage practices of emerging native XML environments, programmers and software designers can better exploit the tech-nology's scalability and reliability benefits. Understanding the environments' structure is also useful Because XML is rapidly becoming the Internet standard for data representation and exchange, efficient XML document storage has become a core data management issue. Most early XML storage practices rely on conventional database management systems. However, such systems involve mappings and …