16. A system for providing thematic information to provide a visual theme for documents, comprising: a computer readable storage medium encoded with a theme object for conveying thematic information for visual display of documents; wherein the theme object is defined using a markup language and is stored in a theme file; wherein the definition of the theme object is maintained separately within the theme file from other objects that define the document and that are each maintained separately; and wherein a schema defines and enforces rules for displaying the theme object; an operating system executed on a processor; wherein the operating system provides an application programming interface (API) to the theme object; an application suite executed on a processor; wherein the application suite comprises a first application for authoring a first kind of document using the API to the theme object, and comprising a second application that is different from the first application for authoring a second kind of document using the API to the theme object; wherein the first kind of document is associated with a first file format that includes modular parts that are associated together; wherein the theme object is a modular part that is associated with the first file format; wherein the second kind of document is associated with a second file format that includes modular parts that are associated together; wherein the theme object is a modular part that is associated with the second file format; wherein the theme object provides a common appearance for the first kind of document and the second kind of document.
16. A system for providing thematic information to provide a visual theme for documents, comprising: a computer readable storage medium encoded with a theme object for conveying thematic information for visual display of documents; wherein the theme object is defined using a markup language and is stored in a theme file; wherein the definition of the theme object is maintained separately within the theme file from other objects that define the document and that are each maintained separately; and wherein a schema defines and enforces rules for displaying the theme object; an operating system executed on a processor; wherein the operating system provides an application programming interface (API) to the theme object; an application suite executed on a processor; wherein the application suite comprises a first application for authoring a first kind of document using the API to the theme object, and comprising a second application that is different from the first application for authoring a second kind of document using the API to the theme object; wherein the first kind of document is associated with a first file format that includes modular parts that are associated together; wherein the theme object is a modular part that is associated with the first file format; wherein the second kind of document is associated with a second file format that includes modular parts that are associated together; wherein the theme object is a modular part that is associated with the second file format; wherein the theme object provides a common appearance for the first kind of document and the second kind of document. 17. The system of claim 16 wherein the first application is a spreadsheet application and the second application is a word processing application.