ANNA UNIVERSITY M.E CSE REG-2013
Anna University - CP7202 Advanced Databases Study Material Free Download
CP7202 Advanced Databases - Unit 5 EMERGING TECHNOLOGIES Study Material Free Download
Structured, Semistructured, and Unstructured Data
XML Hierarchical (Tree) Data Model
XML Documents, OTO, and XML Schema
XML Documents and Databases
XML Querying
Summary
Review Questions
CP7202- Advanced Database XML and Internet Databases:
STRUCTURED, SEMISTRUCTURED, AND UNSTRUCTURED DATAThe information stored in databases is known as structured data because it is represented in a strict format. For example, each record in a relational database table-such as the EMPLOYEE table in Figure S.6-follows the same format as the other records in that table. For structured data, it is common to carefully design the database using techniques such as those described in Chapters 3, 4, 7, 10, and 11 in order to create the database schema. The DBMSthen checks to ensure that all data follows the structures and constraints specified in the schema.
However, not all data is collected and inserted into carefully designed structured databases. In some applications, data is collected in an ad-hoc manner before it is known how it will be stored and managed. This data may have a certain structure, but not all the information collected will have identical structure. Some attributes may be shared among the various entities, but other attributes may exist only in a few entities. Moreover, additional attributes can be introduced in some of the newer data items at any time, and there is no predefined schema. This type of data is known as semistructured data. A number of data models have been introduced for representing semistructured data, often based on using tree or graph data structures rather than the flat relational model structures. A key difference between structured and semistructured data concerns how the schema constructs (such as the names of attributes, relationships, and entity types) are
handled. In semistructured data, the schema information is mixedin with the data values, since each data object can have different attributes that are not known in advance. Hence, this type of data is sometimes referred to as self-describing data. Consider the following example. We want to collect a list of bibliographic references related to a certain research project. Some of these may be books or technical reports, others maybe research articles in journals or conference proceedings, and still others may refer to complete journal issues or conference proceedings. Clearly, each of these may have different attributes and different types of information. Even for the same type of reference-say, conference articles-we may have different information. For example, one article citation may be quite complete, with full information about author names, title, proceedings, page numbers, and so on, whereas another citation may not have all the information available. New types of bibliographic sources may appear in the future for example, references to Web pages or to conference tutorials-and these may have new attributes that describe them.
<html>
<head>
</head>
<body>
<H1>List of company projects and the employees in each project<\H1>
<H2>The ProductX project:</H2>
<table width="100%" border=O cellpadding=O cellspacing=O>
<TR>
<TO width="50%"><font size="2" face="Arial">John Smith:</font></TO>
<TO>32.5 hours per week</TO>
</TR>
<TR>
<TO width="50%%"><font size="2" face="Arial">Joyce English:</font></TO>
<TO>20.0 hours per week</TD>
</TR>
</table>
<H2>The ProductY project:</H2>
<table width="100%" border=O cellpadding=O cellspacing=O>
<TR>
<TO width="50%"><font size="2" face="Arial">John Smith:</font></TO>
<TO>7.5 hours per week</TO>
</TR>
<TR>
<TO width="50%%"><font size="2" face="Arial">Joyce English:</font></TO>
<TO>20.0 hours per week</TO>
</TR>
<TR>
<TO width="50%%"><font size="2" face="Arial">Franklin Wong:</font></TO>
<TO>10.0 hours per week</TO>
</TR>
</table>
</body>
</html>
<head>
</head>
<body>
<H1>List of company projects and the employees in each project<\H1>
<H2>The ProductX project:</H2>
<table width="100%" border=O cellpadding=O cellspacing=O>
<TR>
<TO width="50%"><font size="2" face="Arial">John Smith:</font></TO>
<TO>32.5 hours per week</TO>
</TR>
<TR>
<TO width="50%%"><font size="2" face="Arial">Joyce English:</font></TO>
<TO>20.0 hours per week</TD>
</TR>
</table>
<H2>The ProductY project:</H2>
<table width="100%" border=O cellpadding=O cellspacing=O>
<TR>
<TO width="50%"><font size="2" face="Arial">John Smith:</font></TO>
<TO>7.5 hours per week</TO>
</TR>
<TR>
<TO width="50%%"><font size="2" face="Arial">Joyce English:</font></TO>
<TO>20.0 hours per week</TO>
</TR>
<TR>
<TO width="50%%"><font size="2" face="Arial">Franklin Wong:</font></TO>
<TO>10.0 hours per week</TO>
</TR>
</table>
</body>
</html>
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