XForms Essentials

A Brief Review of HTML Forms

The introduction of the forms chapter in HTML 4.01 reads: “An HTML form is a section of a document containing normal content, markup, special elements called controls (checkboxes, radio buttons, menus, etc.), and labels on those controls. Users generally ‘complete’ a form by modifying its controls (entering text, selecting menu items, etc.), before submitting the form to an agent for processing (e.g., to a web server, to a mail server, etc.).”

The defining element for HTML forms is named, not too surprisingly, form. This element describes some important aspects of the form, including where and how to submit data. The content of this element consists of regular HTML markup, as well as controls.

Forms represent a structured exchange of data. In HTML forms, the structure of the collected data, called a form data set, is a set of name/value pairs. The names and values that are included in this set are solely determined by the controls present within the form, so that adding a new control element, as well as adding to the user interface, also adds a new name/value pair to the data set. Many authors take for granted this basic violation of the separation between the data layer and the user interface layer—a problem that XForms has gone to considerable lengths to alleviate.

Which control types are available in HTML forms? The following sections will answer this question.

Single-Line Text Input

The workhorse of HTML forms, this control permits the entry of ...