Conclusions and discussion

Many of the issues that ought to be addressed for meeting the requirements of the supposed ideal PSS are receiving scientific attention and dedication. Generally, the developments proceed steadily and promising paths are being explored. A large amount of the ongoing research, however, does not originate from the notion of ideal PSS because many topics are fundamental and require solutions from fields of research such as GIS, visualization and user interface techniques. Hence, advances in PSS development are largely dependent on the advances made with regard to a combination of technologies. At the same time, the reality of planning practice makes it mandatory to deliver PSS as one- off applications in response to the characteristics of the typical problem and/or situation they should address. In many cases, the aim is to support a part of the planning process (i.e., a certain range of decisions), requiring only ‘partial’ solutions. For instance, when the supported part requires decision-making based on insights into 2D aspects, the system should focus on optimizing the provision of that particular support; more complex 3D or 4D models would be redundant. The dissimilarity between systems can also be a result of differences in the intended user groups or the objectives regarding system usage, causing variation in, for instance, the provided set of models or the degree to which such models are integrated. Overall, PSS developments remain largely uncoordinated, which causes disorientation from the goal that should bind them in order to ever reach ideal PSS.

In order to streamline developments it is crucial to pay attention to the conceptual framework of PSS. Following from the situation described above, efforts must be made to develop a framework that is both generic in providing the key building blocks needed for any PSS and flexible in accounting for the singularities of specific cases. Important to bear in mind here is that, despite their indispensability regarding system functionality, the required technological components should not drive system structure but serve only

supportive purposes. This is especially important in the light of GIS that, for long, has been ascribed a core position within PSS, constituting the information component. Recent developments, however, show that a re-evaluation is taking place that turns GIS into a serving instead of ruling component focussed on provides data management and mapping functionality. This widely accepted repositioning of GIS to the background of PSS – like the visualization component – forms a perfect starting point to reconsider the framework of PSS in the light of their ideal.

Obviously, shifting GIS to the background implies that an alternative way needs to be found to structure and organize PSS in general terms. Since the particularities of planning are basically assimilated by the models component, it is practically self-evident to consider this as the component that ought to be most central and directive within the framework of PSS. In its operation as core component, support should be conjointly provided by the information and visualization components, while the user interface should take care of optimizing the system appearance and usability. For defining a suitable and viable PSS framework, however, it is obviously not simply a matter of reassessing the roles of components and rearranging them. Essentially, it requires attention for all aspects that determine the operation of PSS as coherent assemblages of components and as instruments to users.

Experiences show that the complexity and diversity of problems in areas such as planning can only be appropriately addressed by means of systems that demonstrate

intelligence stretched out over several dimensions. For instance, intelligence is required for system flexibility – in terms of extensibility and adaptability – as it is certain that successive changes will occur in requirements coming from planning practice as well as in the technological and methodological instruments delivered by industry and science. Subsequently, the variety and complexity of models and data to be bundled by PSS demand intelligence along two dimensions. First, it is needed to ensure flawless information and control flows of models and data, implying a smooth integration of system components, ideally yielding synergy. Second, intelligent solutions are needed with concern to the user interface. PSS should not only demonstrate a consistent sensitivity to user characteristics, information types and information usage by providing various operation modes, they should also remain comprehensible to users irrespective of the depth and width of their functionality, which requires user assistance that is intelligent in terms of avoiding information overload and augmenting the limitation in skills of users. Moreover, user assistance should be anticipatory, corrective, explanatory, guiding, and so

on, in a non-obtrusive manner.

It is manifest that PSS will not only benefit from intelligence that optimizes their operation but just as well from intelligence that improves the support of decision-making to users. Research that has been conducted with concern to DSS-ES integration illustrates that the centrally positioned models component is eligible for intelligent sophistication in a dual manner. On the one hand, PSS would greatly benefit from intelligent solutions regarding model management and model construction, as the selection of appropriate models and the development and incorporation of new models are often difficult and time-consuming tasks for users. On the other hand, the use of generally every model would strongly improve when intelligence is present to assist with input preparation (e.g., use of subjective knowledge for problem formulation) and output interpretation (e.g., use of judgemental and explanatory capabilities).

Considering the argued central position of the models component within the PSS framework, the question of what aspect to use for structuring the framework could be traced back to the question of what should basically structure the models component. As stated before, models within PSS address specific stages of the planning process and, most ideally, jointly cover the whole process from problem identification until the choice after evaluation. So to say, the planning process forms the actual blueprint of the models component and, thus, it should do so for the framework of PSS as well. At least, this holds in general terms, as it will depend on the exact purpose of each process how it will be structured in detail and what range of models will need to be provided. The requirements for the information and visualization components follow from this, alike the needs regarding the user interface.

Planning decision-making generates highly frequent needs for expertise from a variety of disciplines. Although the knowledge contained by the models component of PSS can be of various types and concern various disciplines, it is traditionally encapsulated in the mechanisms of models. This makes it hard at best to retrieve any specified piece of knowledge. Moreover, the knowledge provided altogether in PSS often exhibits missing parts. In other words, the required expertise is usually hidden and incomplete, complicating both its use and its management. Accordingly, there are good reasons to expand the framework of PSS with a component that explicitly incorporates the specialized knowledge from the various disciplines involved in planning. Since the need for expertise originates from within the planning process, the component in question should obviously form a duality with the process-related models component. In search for

ideal PSS, the operation of this knowledge component should go beyond that of a plain repository and be intelligently connected with every single part of the framework. Namely, synergy lies ahead when knowledge is utilized for the operation of other components (to generate data, to function as model input or to be a source for user assistance), while at the same moment the other components form the very sources for knowledge retrieval.

The success of PSS deployment will highly depend on the degree to which the required dimensions of intelligence can be realized. PSS will not be considered useful, and will definitely not convince users of their potential contributions to the decision- making process, as long as they lack the intelligence required to decide on the use of appropriate types of knowledge and the right kind of information to solve planning problems. Nor they will, when they overwhelm users by releasing too much of their inherent complexities. Basically, the incorporation of intelligence in PSS requires the use of methods and techniques from the areas of artificial intelligence and knowledge engineering. As a branch of artificial intelligence, multi-agent technology offers promising concepts and techniques that give it the potential to improve PSS with concern to both system usage and system capabilities. For instance, it perfectly matches the strong demand of planners for disaggregate models, while also providing the means to realize the desired knowledge component. At the same time, it has the potential to serve the purpose of organizationally structuring PSS in a way that facilitates all kinds of internal control flows and still remain most natural to human users. The next chapter will provide an introduction to the area of multi-agent technology and explain how this technology is believed to play a crucial role in the quest for ideal PSS.

3 MULTI-AGENT TECHNOLOGY AND