Chapter 28 Web programming
Objectives
- To show how web client-server interactions are implemented.
- To introduce the notion of the web as generic middleware: the possible use of web browser front-ends for general services
and databases, rather than merely for document delivery.
Points to emphasise
- The document paradigm is central to the original web concept. Original markup as HTML. Generic markup as XML plus
separate DTDs.
- The realisation of the components of any distributed system: a protocol, client software, application and system services. How
naming and location are supported (above DNS).
- Web documents are ?read mostly? which allows the use of caching and replication for efficiency and scalability. Concurrency
control is simple for read mostly documents but the web is increasingly being used for database front-ends.
- The need for trusted, secure channels for services such as e-commerce. Refer to Chapter 8 and SSL. The need to protect
clients? systems from incoming applets and scripts.
Possible difficulties
HTML is easily visible. XML may not be within students? experience. The distinction is important and XML is becoming
widely used for transmission and storage of typed data.
Teaching hints
Give, or draw on, practical experience. It's fun to create web pages. But extend to the need
for secure access , forms, scripts and applets.