A Heterogeneous Database System is an automated (or semi-automated) system for the integration of heterogeneous, disparate database management system

Database management system

A database management system is a software package with computer programs that control the creation, maintenance, and use of a database. It allows organizations to conveniently develop databases for various applications by database administrators and other specialists. A database is an integrated...

s to present a user with a single, unified query interface.

Heterogeneous database systems (HDBS) are computational models and software implementations that provide heterogeneous database integration [1,2]

Problems of Heterogeneous Database Integration

This article does not contain details of Distributed database management system

Distributed database management system

A distributed database management system is a software system that permits the management of a distributed database and makes the distribution transparent to the users. A distributed database is a collection of multiple, logically interrelated databases distributed over a computer network...

s (sometimes known as Federated database system

Federated database system

A federated database system is a type of meta-database management system , which transparently integrates multiple autonomous database systems into a single federated database. The constituent databases are interconnected via a computer network and may be geographically decentralized...

s).

Technical Heterogeneity

Different file format

File format

A file format is a particular way that information is encoded for storage in a computer file.Since a disk drive, or indeed any computer storage, can store only bits, the computer must have some way of converting information to 0s and 1s and vice-versa. There are different kinds of formats for...

s, access protocols, query languages etc. Often called syntactic heterogeneity from the point of view of data.

Data Model Heterogeneity

Different ways of representing and storing the same data. Table decompositions may vary, column names (data labels) may be different (but have the same semantics), data encoding

Code

A code is a rule for converting a piece of information into another form or representation , not necessarily of the same type....

 schemes may vary (i.e. should a measurement scale be explicitly included in a field or should it be implied elsewhere). Also referred as schematic heterogeneity.

Semantic Heterogeneity

Data across constituent databases may be related but different. Perhaps a database system must be able to integrate genomic and proteomic data. They are related - a gene may have several protein products - but the data is different (nucleotide sequences and amino acid sequences, or hydrophilic/phobic amino acid sequence and positive/negatively charge amino acids). There may be many ways of looking at semantically similar, but distinct datasets.

The system may also be required to present 'new' knowledge to the user. Relationships may be inferred between data according to rules specified in domain ontologies.

See also

• Ontology
  Ontology (computer science)
  In computer science and information science, an ontology formally represents knowledge as a set of concepts within a domain, and the relationships between those concepts. It can be used to reason about the entities within that domain and may be used to describe the domain.In theory, an ontology is...
  
  
• Knowledge Base
  Knowledge base
  A knowledge base is a special kind of database for knowledge management. A Knowledge Base provides a means for information to be collected, organised, shared, searched and utilised.-Types:...
  
  
• Expert System
  Expert system
  In artificial intelligence, an expert system is a computer system that emulates the decision-making ability of a human expert. Expert systems are designed to solve complex problems by reasoning about knowledge, like an expert, and not by following the procedure of a developer as is the case in...