Databases

Relational Databases

• Set of named relations (tables)
• Each relation has a set of named attributes (columns)
• Each tuple (row) has a value for each attribute
• Each attribute has a type (or domain)
• All queries return relations (tables), so it can said to be compositional or closed.

XML Data

• Alternative to relational model to store data
• Standard for data representation and exchange
• Document format similar to HTML, however tags represent content instead of formatting.
• XML consists of tagged elements which can be nested, attributes of elements and the text (values/data)
• XML document can be thought of as a tree with values/text forming the leaves.