英语翻译Regarding the data model concepts provided by RDBS and X

英语翻译
Regarding the data model concepts provided by RDBS and XML,there are fundamental differences leading to data model heterogeneity,which aggravate the integration of both paradigms.Heterogeneity with respect to data models is mainly due to the different purposes RDBS and XML have been developed for.The aim of RDBS is to store large amounts of data enabling efficient access and ensuring their consistency [5].In contrast,XML is intended to serve as a format for structuring and exchanging hypertext documents [1,66].Data model heterogeneity is discussed in the following subsections focusing on typing mechanisms,null values and default values,identification,relationships,and order of instances.Since from a database perspective,many concepts supported by DTDs are insufficient for schema definition,e.g.,the typing mechanisms,XML is often referred to as a data format,only,having no appropriate data model.Consequently,there have been strong efforts to supplement DTDs by means of the richer XML schema specification language XML Schema.In contrast to DTDs XML Schema is expressed by means of XML itself.Extensions include a richer set of primitive data types as well as a mechanism to enable inheritance.Although the use of XML itself as language to specify various schemata allows to reuse existing XML tools for schema validation,the use of XML Schema is by far more complex than simply using DTD syntax.