For several reasons and since their appearance, the SCADA systems have always been a specific kind of software engineering. They formally are big and complex in the functionality they provide, but mostly, they have to follow very strict requirements in the matters of performance and availability. Traditional1y, these proprietary applications are closed and difficult to inter-operate with. Each software provider has its own, complete, SCADA system with a small degree of integration with others'.

It is, therefore, a very stabilised kind of software, somewhat insensible to broader changes, even with respect to the big revolution that the Web is operating on the software engineering in genera1.

In this thesis, we propose a different approach for the implementation of SCADA applications. We'll base ourselves in some of the Web principles, specifically, using "Web Services" as a transport layer in the communication between applications. This way, we'll try to improve these applications in what concerns interoperability, portability and versatility in the geographical location of system' operators, but keeping in mind the strict requisites of this area.

We'll build a communications' framework, implementing a publish/subscribe paradigm, based on topics. We'll provide two transport implementations, the first based on a common middleware technology (RMI) and the other based on Web Services (SOAP).

With this framework, we'll build an exploration set, with the necessary applications and scenarios to evaluate the fulfilment of the SCADA requisites.

The obtained results are satisfactory, both in the comparison between the Web and RMI implementations, as in the fulfilment of the referred requisites. This shows that it is possible to adapt the traditional SCADA systems to the new Web technologies.