| Needs work: Expand example ( w. code ), ID-REFS, XLink http://www.ibm.com/developerworks/xml/library/x-xdm2m.html |
Logical data modeling usually occurs largely at a high level, outside the constraints of particular technologies, such as XML or SQL. However, since the resulting data model will ultimately be implemented in one ( or more ) of the available technologies, the logical data model might be adjusted for the particular computing system on which the physical data model is to be implemented – in this case, XML.
A logical data model consists of three main components: entities, attributes, and relationships (http://web.archive.org/web/20080509063521/http://www.dbmsmag.com/9506d16.html ). XML provides a robust platform for implementing entities and attributes, but relationships can be more difficult to express ( http://www.tdan.com/view-articles/5538 ).
The hierarchical structure of XML can be used to convey basic relationships, such as one-to-one and one-to-many; for example, a document called ‘Module’ can contain one or more ‘Tutor’ elements. This can be thought of as expressing either an one-to-one relationship ( if the module only has one tutor ), or as one-to-many, if the module contains multiple ‘Tutor’ elements.
