Sonderband 2. International Council on Archives. Dritte Europäische Archivkonferenz, Wien 11. bis 15. Mai 1993. Tagungsprotokolle (1996)

4. Session / Séance. Strategies for Links with Historical Research / Stratégies de Communication envers la Recherche historique - Gonzalez, Pedro: Data Bases and Long Distance Communication. A Spanish Éxperience / Bases de données et information a distance. Une expérience des archives espagnoles (english 319 - français 343)

6 .2. Conditioning factors of the AGI System for remote Access

The system developed for the AGI provides a number of characteristics which differentiate it from the most usual forms of access to remote data bases, especially to the traditional ASCII data base.

6. 2. 1. Distributed Process, Client-server Architecture

The concept of distributed process with which the system has been developed is the first of the conditions. It is not a central computer which does the work and to which the remaining terminals have access. The process is really distributed among the different servers and user stations (server-client) so that, for example, a request to the digital image storage system gives rise to the dispatch of the images which make up an Archive document, by the corresponding server. These images, through the Network, reach the user station and are then stored in its hard disk. But all the tools for processing and improving the image are held in the user station, as is the intelligence of the system, in order to be able to analyze the way in which the user screens the pages of a document on many pages, and how he requests that these pages be sent at a rate which adapts as far as possible to the speed of look-up.

Something similar happens to the text data base. The data bases server sends its response to the user. But its final presentation is only obtained through the operations carried out in cooperative process, through the User Interface Subsystem. The user station, with graphical interface, carries out the necessary operations for a presentation of the information which is far superior to the traditional ugly terminal screens.

What this means, in short, is that the user station for remote access must be not a classic terminal, but an intelligent station with all the necessary software (OS/2), Presentation manager and the System’s software.

6. 2. 2. Hardware

Also specific hardware limits remote access to the AGI system. Firstly, a microcomputer capable of handling the above-mentioned software is required, at least with a 486 processor and 16 Mb of main memory. Moreover, if document images are to be screened, a monitor with adequate resolution will be required (1600 x 1200 dpi). The monitors used in Seville are IBM 8508 for images in grey, or IBM 6091 for colour images.

6. 2. 3. Transmission line Capacity

As we have been saying, the speed and ability of conventional data transmission lines is sufficient for sending small quantities of information over great distances. In contrast, sending high resolution digital images is not something as cost-effective and easy to achieve. Many minutes are used up in sending one single 100 Mb image on 2400 or 9600 b/s lines. Only the extension of broad band lines, with the introduction of more powerful compression algorithms, will make these dispatches more cost-effective.

4. Session/Séance: Gonzalez, Data Bases and long distance Communcation

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