12.3 Oval - A Toolkit to Build Information Exploration Interfaces
Thomas Malone has led the development of a series of systems first called Information Lens, later Object Lens, and most currently Oval, that incorporate many of the features described above [Crow88] [Lai88] [Lai91] [Mal92]. Oval uses ideas from artificial intelligence and user interface design to represent information in a way that can be processed intelligently both by human beings and by computational agents. It integrates ideas from the fields of hypertext, object-oriented databases, electronic messaging and rule-based intelligent agents [Lai88] [Mal92]. Its particular focus is on the development of applications for cooperative work, but most of the ideas can easily be applied to other domains. Malone calls his system radically tailorable[Mal92], because new applications can be simply built using the four basic building blocks objects, views, agents, and links. Oval is semiformal in the sense that it is well suited to process formally specified information, but that the formal specification can easily be changed. Oval distinguishes between passive information, that is represented in semistructured objects with template-based interfaces, and active rules for the processing of the passive information. Views specify the interface of the object to the users and allow them to edit instances of the object; links represent the relationships between the objects. Radical tailorability allows users to
- easily define new object types
- add fields to existing object types
- select views for objects and collections of objects
- specify the parameters for a view
- create new agents and rules
- insert new links.
Malone and Lai use the power of radical tailorability to easily reimplement other cooperative work applications.
Objects in Oval represent familiar things such as messages, people, meetings, tasks, manufactured parts and software bugs [Lai88]. The information in the objects is semistructured in the sense that users are free to fill in as much information into the different fields as they want. Fields can also be in free-text format. Figure I.67 shows one instance of an object that can be edited in a template editor.
Figure I.67 Template editor for objects (ExFig 1 from [Lai88])
Objects and object hierarchies are defined by a set of templates. By clicking on the template of an object and selecting the appropriate command from a menu, users can modify an object (Figure I.68).
Figure I.68 Object hierarchy defined by templates (ExFig 3 from [Lai88])
To perform an action on an object, the user creates an agent. The behavior of the agent is specified by a collection of rules that are created with a rule editor (Figure I.69). In this example the rule specifies what has to happen to e-mail messages. Rules consist of "IF" and "THEN" parts, that are applied to the current object.
Fig. I.69 Rule describing actions on objects (ExFig 6 from [Lai88])
The real power of the Oval system comes from the combination of objects and agents, where objects are displayed in views and manipulated by agents, while relationships between the objects are expressed by links. Oval is thus particularly well suited for manipulating active information, i.e., information that is accessed in different form by different persons, as, e.g., e-mail. Indeed, e-mail was one of the first applications of Information Lens, the first-generation predecessor of Oval.
Contrary to guides, agents react based on an analysis of the real contents of the document. As Oval illustrates, the behavior of agents is defined by rules. But there is still a long way to go until agents will take over our daily duties we do not want to do anymore, and will, for example, go out to search the Internet autonomously for the book that we did not find in our local library.