H

Hardware:

The computer or machine that software runs on (see Software ). Hardware includes the computer, disk drives , CPU, memory, and so on.

HAVING Clause:

A specialized SQL query filter applied only to the results of a GROUP BY clause (see GROUP BY Clause ).

Heterogeneous System:

A computer system consisting of dissimilar elements or parts . In database parlance, this implies a set of applications and databases, where database engines are different. In other words, a company could have a database architecture consisting of multiple database engines, such as MSAccess, Sybase, Oracle, Ingres, and so on. All databases, regardless of type, are melded together into a single, and apparently one and the same, transparent database-application architecture. This can obviously become incredibly complex and is, in reality, an unlikely scenario.

Hierarchical Structure:

A structure where there is a root node, which contains one or more child nodes, where each child can contain one or more child nodes, and so on. XML documents are hierarchically structured in this fashion.

Homogeneous System:

Everything is the same, such as database engines, application SDKs, and so on (see Heterogeneous System ).

HTML:

HyperText Markup Language.

HTML DOM:

The HTML Document Object Model.

Hypertext Markup Language:

The most basic of all Internet browser scripting languages. HTML is inflexible but relatively powerful and unlike XML, has a set number of allowable tags.

Hyperlink:

Refers to a link between web pages. In HTML a hyperlink (or link) is defined using a tag. In XML, hyperlinks can be defined dynamically using XLink and XPointer definitions.