Storing Application Specific Data

Subject

This tutorial describes the use of 'Metadata' to extend the capabilities of the core Whitebeam system beyond the capabilities originally envisaged by the designers.

Overview

One of JavaScript's many strengths is the ability to dynamically create arbitrarily complex data structures. Unlike many programming languages these types do not need to be rigorously defined upfront and designed into the system. Instead an object can be created and properties added to it at will. There is no 'class definition' that lays down membership rules for JavaScript objects. Consider the following code fragment:

var anObject     = new Object;
anObject.name    = "Fred";
anObject.sname   = "Bloggs";
anObject.company = "Whitebeam";
anObject.age     = 28;


anObject.job     = "engineer";


This allows for rapid application development and modification. The Whitebeam System is designed to work with and harness this flexibility. There is limited usefulness in a system that provides the designer with such a powerful development tool as JavaScript then handicaps that is real applications by not providing some level of that flexibility in the underlying application code. Consider the above example again. The Whitebeam System provides business templates that encapsulate some functionality. These templates are provided by Whitebeam. But they need to be extensible in the same way the JavaScript object is extensible - quickly and easily. Extending the example above - suppose the properties of the object are to be stored in a template. If the template were initially designed just for the initial four properties the designer would have to come back to Whitebeam and ask for a modification. Every designer would want something different!

The JavaScript extensibility concept is harnessed by the Whitebeam System to allow Integration Partners to easily enhance their applications beyond the basic functionality defined by Whitebeam. In the Whitebeam environment these arbitrary structures are referred to as 'Metadata' objects.

Within JavaScript these objects are no different from any other JavaScript object. Whitebeam's flexibility comes in the ability to integrate these objects easily into the non-JavaScript aspects of the system. Many Whitebeam Business Templates can store these arbitrary structures transparently. In effect providing integration partners to extend the basic data set of a template to suit the specific requirements of their customers. The system allows the objects to be stored in client side cookies or in server side session data.

As far as the Integration Partner or Web Designer is concerned Metadata objects are simply JavaScript objects. The programmer defines the properties of that object in any form they require for their application. Some of the properties can be simple strings, others can themselves be objects or arrays containing other objects and arrays etc.

Once the object has been defined the Whitebeam Environment provides the means of storing those objects in various 'useful' places - consider the power of being able to create your own set of properties and being able to store those against, say, a persons data, or along with a catalogue item. Or storing as set of arbitrary data items against a user session.

A simple example is that of the rb.page.session object that allows authors to store session data to be retrieve during later requests.