Other Data Models

Attribute Lists

There is a strong relationship between XML documents and semistructured data. Assume that for some pair of matching tags and in a document we make a node n. Then, if and are matching tags nested directly within the pair and (i.e., there are no

Document Type Definitions

In order for a computer to process XML documents automatically, there needs to be something like a schema for the documents. That is, we need to be told what tags can appear in a collection of documents and how tags can be nested. The description of the schema is given by a

XML and Its Data Model

XML (Extensible Markup Language) is a tag-based notation for "marking" documents, much similar to the familiar HTML or less familiar SGML. A document is nothing more nor less than a file of characters. However, while HMTL's tags talk about the presentation of the information

Information Integration Via Semistructured Data

Unlike the other models we have discussed, data in the semistructured model is self-describing; the schema is attached to the data itself. That is, each node (except the root) has an arc or arcs entering it, and the labels on these arcs tell what role the node

Semistructured Data Representation

A database of semistructured data is a collection of nodes. Each node is either a leaf or interior. Leaf nodes have associated data; the type of this data can be any atomic type, such as numbers and strings. Interior nodes have one or more arcs out. Each arc has a label, which shows

Semistructured Data

The semistructured-data model plays an important role in database systems: 1. It serves as a model appropriate for integration of databases, that is, for describing the data included in two or more databases that include similar data with different schemas.

From ODL Designs to Object-Relational Designs

In “From ODL Designs to Relational Designs” we learned how to convert designs in ODL into schemas of the relational model. Difficulties arose primarily because of the richer modeling constructs of ODL: nonatomic attribute types, relationships and methods. Some, but not all, of

Object-Oriented Versus Object-Relational

The object-oriented data model, as typified by ODL, and the object-relational model discussed here, are outstandingly similar. Some of the most important points of comparison follow.


The fact that movies like Star Wars will appear in various relations that are values of the movies attribute in the nested relation Stars is a cause of redundancy. In effect, the schema of Nested Relations Example (a) has the nested-relation analog of not being in BCNF. On the

Nested Relations

Relations extended by point (1) of The Object-Relational Model are sometimes called "nested relations''. In the nested-relational model, we allow attributes of relations to have a type that is not atomic: particularly, a type can be a relation schema. Thus, there is a convenient,

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