Semi Structured Data Model in Database

Semi Structured Data Model in Database

Semi Structured Data Model in Database

 

Semi-Structured Data Model is based on labelled graphs rather than labelled trees.It allows allow cyclic references.Schema is usually contained within the data, which is sometimes called self-describing.Schema information is in the edge labels and the data is  stored at the leaves.It provides a flexible format for data exchange between different types of databases.Certain forms of semi-structured data have no separate schema.
   
Semistructured data has recently emerged as an important topic of study and research. There are huge amount of data in the World Wide Web.The data in the web are not structured, but there is huge requirements of querying/integrating/exchanging information on web.

Since it is a semi-structured database model,the queries cannot be made as efficient as in a more constrained structure like relational model.SQL is used to query relational data.Xpath is used to navigate through elements and attributes in XML document.XQuery is used to query XML data.

XML Schema and DTD can be used describe the structure of XML document, that is we can use this to validat an XML document. But it is not mandatory to have XML schema or DTD for an XML document,it is optional.