ERCIM News No.20 - January 1995 - INRIA

OPERA - Editing Complex Structured Documents

by Vincent Quint

Electronic documents is the main interest of project "Opera" at Inria. When the project was launched, the emphasis was put on the logical structure of documents and on the tools needed for editing complex structured documents in a user-friendly way. The main result of this work is the structured editor "Grif".

Since that time, the scope of the project has been broaden and additional topics are now considered, such as active documents, multimedia, and cooperative editing. These new research issues are not independent from the initial orientation. The document logical structure is involved wherever it may help. In addition, research on structured documents is still active in the project. It specially concerns layout and structure transformation. The problems addressed in the field of layout are those posed by the coexistence, in an interactive system, of a rich, abstract logical structure and a complex graphical presentation. The logical structure considers such elements as chapters, titles, sections, paragraphs, tables, figures, equations, notes, bibliographies, cross-references, etc. with all their relationships, while the graphical structure involves pages, columns, footers, blocks, etc. Some graphical components are directly related with logical elements (each paragraph is displayed within a block, for instance), but some others are independent (e.g. pages and columns). The objective is to let the user interactively manipulate the logical structure and have the system dynamically format the document, according to some specification of the graphical structure and its relationships with the logical structure.

Structure transformation is also a key issue in a system where the emphasis is put on the logical structure. The structure should help users to produce better documents, it should not be felt as a constraint. For that purpose, an editor must provide users with powerful and flexible commands that transform the structure of a document. For instance, the structure of a document part must be automatically modified when that part is copied or moved in some other part of a document, where its current structure is not acceptable.

An interactive editor for structured documents is often considered as a tool that is part of a larger application handling documents and other kinds of information. For that reason, the architecture of the editing tool developed in the project is open-ended. It allows developers to integrate (some parts of) the editor within another application, by the means of the active document concept: the application can control the editor and react to each editing operation performed by a user.

This active document concept is used for developing a cooperative editor called Alliance. It allows several users distributed across the Internet to simultaneously work on the same documents, in a coordinated way. The application takes advantage of the logical structure for dividing documents into fragments which are used for controlling access rights and document consistency.

Documents have not only a logical and a graphical structure. They also have a time structure which expresses the time relationships between multimedia components. This new type of structure is currently under definition, and will be added in the available editing tools. This work, together with the connection of sound and video players, will extend our editing tools for the manipulation of multimedia documents, combining time-dependent media and high-level structures.

Most of the results of the project are applied to the development of tools for the World Wide Web. The main objective is to develop tools for collaborative authoring of multimedia distributed documents.

Please contact:
Vincent Quint - INRIA
Tel: +33 76 63 48 31