The Object-Action (or visa-versa) model and its applications

From Computing and Software Wiki

Contents 1 Background 1.1 Object Action Interface 1.2 Action Object Interface 2 Scope 2.1 Example 3 Principles 3.1 OAI Model 3.2 Syntactic Knowledge 4 Task hierarchies of objects and actions 4.1 User 4.2 Designer 5 Interface hierarchies of objects and actions 5.1 Interface Objects 5.2 Interface Actions 5.3 User 5.4 Designer 6 Limitations and Challenges 6.1 Metaphor Interpretation 6.2 Batching and Pipelining 7 References

Background

Object Action Interface or Action Object Interface is changing the way people interact with systems. As more and more systems switch from text mode command based languages to Graphical User Interface (GUI) the problem now lies with visually representing and displaying of user's tasks objects and actions. Before GUI was implemented in systems and users had to remember a set of commands and if they ever had to use a command which was not used frequently they would have to refer to another user of the manual pages.

Object Action Interface is basically an extension to the Graphical User Interface, it also relates to Direct Manipulation User Interface. DMUI can help create better Human Computer Interfaces and can also increase the usability of the product

There are two basic interaction models for any given system.

Object Action Interface

In this model the user will select the object first and then select the action which will be performed on the object.

Example: In Windows, if you want to copy a file you will first select a file (Object) and then right click and select copy (Action).

Action Object Interface

In this model the user will select an action and then select the object the action will be performed on.

Example: In command prompt, if you want to copy a file you will input copy <Source File> <Destination File>. 'Copy' which is the action comes before the object '<Source File>'

Scope

There has always been distinction between those two models in several domains starting long ao by compiler designers who always wanted to distinguish between syntax, which is different tokens parsed from a source code file, and the semantics, which are the actual operations invoked by that text. Different areas use the syntactic-semantic model of human behaviour, such as programming, database manipulation facilities and direct manipulation (Shneiderman, 1980, 1981)

Example

The difference between the two models can be seen when comparing a command based system (UNIX) to a GUI environment (Windows). The task to copy or move a file from one directory in UNIX is different than in Windows. In UNIX the action of copying is specified first and then object. In Windows the object is first selected then the action of copying is applied.

The Object Action Model is also used in a real life environment. If you want to move a file from one folder to another you will first select the file and then move it. You cannot choose the action of moving and then select the file.

Principles

OAI Model

Syntactic Knowledge

Task hierarchies of objects and actions

Tasks are composed of objects and actions at high and low levels. Not all users will find these hierarchies to be perfect, but since they are comprehensible, a great deal of usefulness is provided.

User

Dividing complex tasks into sub-tasks and solving the sub-tasks independently has been shown to be a successful way to solve larger complex problems. Most real world objects and entities involve the use of this property of creating sub-tasks create a plan of smaller action steps. People learn tasks actions and objects within their lifetime and realize that the process is simplified greatly, when managing different smaller levels within a hierarchy. Issues of implementation are not considered as much when executing tasks using this method.

Designer

Three steps are suggested by Ben Shneiderman, the creator of the 8 golden rules for interface design, for designers to correctly build a task hierarchy.

   1. Know about the users and their tasks (Interviewing users, reading workbooks and taking training sessions)
   2. Generate hierarchies of tasks and objects to model the users' tasks
   3. Design interface objects and actions that metaphorically map to the real world universe

Interface hierarchies of objects and actions

Interface Objects

Interface Actions

User

Designer

Limitations and Challenges

Metaphor Interpretation

Each user's way of performing a task may vary. Defining steps completely with metaphors creates risk in the varying interpretations of metaphors amongst different users. Designers of object-action models must consider the wide range of interpretations that are possible when deciding on metaphors for an object. If there is a serious difference between the designer's interpretation and the user's interpretation of the metaphor used, the meaning of the model will be lost. In this case, all the work done to create the model will be lost and the user will be unable to perform the desired task with the interface.

Batching and Pipelining

Users of UNIX and other command line based systems may find that their usual actions of

References

• Amir Khella, Object Action Interface Model