The ease with which you can develop applications on a PC has caused developers to pay far too little attention to the basic infrastructure in which the systems run. Developers often slap together a form, test it on a PC, and then roll it out to unsuspecting users. They fail to take into account that although they have tested the system on a LAN connection, users will use the system over a WAN connection. What seems fine in one setting is bad in another, and even the world's greatest application really stinks if it's deployed on an inappropriate infrastructure.
Understanding the implications of the infrastructure is even more important in web development, and your designs must account for differences between the major Internet networking protocols (especially statelessness, which we'll look at shortly) and their client/server counterparts. Web systems are centered on a network, so you must account for network traffic in your designs. Even the way you connect your database to the Web has an important impact. You haven't yet written a line of code and you've already got dozens of problems to work out.
An individual piece of content, whether it's a human resources manual or a phone list, is a resource in web parlance. There are two broad classes of resources: static and dynamic. Static resources are files in a certain format: HTML documents (HTML) created through a text or HTML editor, ASCII reports (TXT) created through a batch process, images (GIF, JPEG) created through an image editor, and even movies (AVI, MPEG) or sound (WAV, AU) created through a video or audio capture system. Almost any type of file becomes a static resource when placed in the proper directory on a machine running OAS or WebDB.
The second, much more interesting type of resource is a dynamic resource , a program that creates web content as it runs. For example, you could write a program to dynamically create a list of employee phone numbers from a human resources database. When a user visits this page, your program queries the database and builds the page as it runs. These sites are always up to date because they are built directly from the data's source, so they aren't subject to the vagaries of manual updating. OAS allows developers to use a number of languages, including PL/SQL, Java, Perl, and VRML (Virtual Reality Modeling Language), to develop dynamic resources; WebDB uses only PL/SQL. This book concentrates on developing dynamic resources using PL/SQL.
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