Comparación de resultados entre las expectativas de pregrado y posgrado

As mentioned above, in the observational study, subjects using a non-object-oriented interface (TopView) were found to prefer to use an object => action syntax in 60.75% of instances, despite a number of dissuasive factors (see Chapter 4). Additionally, there were no instances where the subjects using an object-oriented interface (Lisa) attempted to use an illegal action => object command sequence. In general terms this finding can be expressed as, 'an object => action syntax is preferred for the computer supported performance of common office tasks', where, it is assumed that ease of use can be inferred from the preference.

This finding can be combined with the notions of the User Structure for user modelling (expressed in Chapter 2) in order to derive a rudimentary User Model. It is expected that the results of the

subsequent empirical activity can then be used to modify and enhance this User Model as a better understanding of syntax usage is gained.

It was proposed in Chapter 2, that the User Structure should specify the processes and

representations of the user, in general terms. Particular instances of user behaviour during task performance can then be modelled using the structure. Here, a User Structure will be derived which concerns the representations held and the processes performed by the user during the observational study. The structure will focus on the task element of interest, the use of syntax. The User Structure assumes that when performing a task using a given device, the user undertakes two primary activities: assimilation of task instructions and implementation of task goals. To achieve these activities the user must hold a number of successive representations of the task at different levels of description. Each representation is transformed by a specified process into the next representation, which may be expressed at the same or a different level of description. The rudimentary User Structure, see Figure 5.1, attempts to specify the processes and representations pertinent to syntax usage.

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First, the user (of either device) works towards the formulation of task goals in accordance with the task instructions. Due to the artificial experimental setting for the study it is assumed that the subjects did not have any predetermined goals with respect to the tasks or task materials. The processes and representations of the right hand side of the structure are provided as an illustration of a possible method of deriving task goals, i.e. that the text instructions undergo a number of transformations ranging from the perception of single letters to the specification of sentence meaning and the abstraction of task goals. The processes and representations shown here are not intended to be a complete or a correct model of human information processing. It is

recognised that many intermediate representations may be held.

The task goals are expressed as an object action pair. The object and action are unordered initially, as denoted by the curly brackets, { }. The pair are then ordered with the object assuming the primary position. As yet, there is no explanation for why the object should be the first element of the task goal expression.

Following specification of the task goals, the user begins their implementation. The working representation of the task is re-expressed at successively lower levels of description until a specification for physical action is obtained. The two notations for objects and actions (e.g. object and object ’) are used to indicate that the same referent is intended in each case, but that the form of expression for it may differ. For example, object refers to memo (general), whereas object' refers to memo-87 (specific). It is assumed that during this phase the user is aware of the device which is to be used and that s /h e has a knowledge of the requirements for interaction with that device e.g. knowledge of the command words available; knowledge of the required syntax; knowledge of the method of input etc. As this user structure is intended to focus on syntax usage, only the device features of interest will be specified (i.e. the required syntax and the method of input technique).

The ease with which the task goals are achieved can be assumed to depend on the degree of compatibility between the current representation held by the user and the way in which the device requires the task elements to be represented.

The User Structure is applied to provide an example of a Rudimentary User Model, see Figure 5.2. This model is an instantiation of the structure as it describes a particular instance of user

behaviour, as found in the observational study. The model describes the behaviour of a TopView subject, using an object => action syntax. This syntax is not strictly correct, but the device would accept it without providing negative feedback. The other device feature of interest is the method of input, which in the case of TopView is selection by mouse.

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