Home Articles Suggested framework (along with prototype) for realizing Spatial Decision Support Systems (SDSS)

Suggested framework (along with prototype) for realizing Spatial Decision Support Systems (SDSS)

R K Goel
Head, Geomatics Technology Division
Space Applications Centre, Ahmedabad 380053

Decision Making and Decision Support
The process of decision making implies the selection of the best course of action(s) in order to achieve a set of pre-defined objectives within certain constraints. Such a choice of action(s) is made by a decision maker on the basis of logical analysis of facts coupled with his knowledge of the decision making environment/context as well as his experience and intuition. Process involves repeated consideration of feasible alternatives with regard to action, their evaluation, comparison and ultimate selection of the best action. Decision making process is thus iterative, integrative and participative.

It is iterative because a set of alternative actions are generated which the decision maker evaluates and insights gained are input to, and used to define, further analysis.

It is interactive because the value judgments, which materially affect the final outcome, are made by decision maker who have expert knowledge that must be integrated with the quantitative data in the models (analysis logic).

Decision making issues in spatial context could be more complex than usual. The process formulating the analysis logic and objectives (decision rules) in spatial context can become so ill structured that it may not be possible to define or model them adequately. A decision support system which is aimed at helping the decision makers in solving complex problems, should therefore assist a decision maker by providing problem solving environment rather than presenting a solution at one go. In a wider sense a decision support system could be termed as any organizational set up consisting of personnel and other resources which work together in order to provide inputs to high levels using which the top brass makes decisions. However, in a restricted sense, we are concerned with a computerized mechanism which tries to emulate human expertise and supports the decision makers specific on aspects

Framework for Spatial Decision Support System (SDSS)
Spatial Decision Support System SDSS) could be viewed as an integrated computer S/W and H/W package realized, in spatial context, using Geographic Information System (GIS) functionality on data base management, analytical modeling and spatio-tabular display together with a frame work for adopting the decision makers expert knowledge. More specifically it has certain characteristics (listed below) which differentiates it from any other S/W system.

  • It is designed to solve ill-structured or semi-structured problems i.e. where objectives and/or analysis logic cannot be fully defined or modeled.
  • It provides an interface, which is powerful and easy to use.
  • It enables the user (decision-maker) to combine models and data in a flexible manner.
  • It helps the user (decision-maker) to explore the solution space (the various options) by using the models in the system to generate a series of feasible solutions/alternatives.
  • It supports a variety of decision-making styles and can be adapted to provide new capabilities as the needs of user (decision-maker) evolve.
  • It provides an interactive and recursive problem solving environment (process) in which user (decision maker) proceeds by multiple passes, making use of his own experience, knowledge and intuition.

GIS could provide only a mechanism for data integration, management, analysis and output generation in spatial environment. To start with it can be used for making queries on the underlying database in a series of what lies here or where lies this mode. A logical query has to be translated into a series of what lies here and/or what lies this questions. In such a situation a user is expected to articulate his logical query in a series of razor sharp questions. In return he receives descriptive answers which are fuzzy as far decision support is concerned. Fuzzy because the task of making inferences, deductions and conclusions is left entirely with the decision-makers. An example Query system and query, For pre-dominantly trial regions in Santrampur Taluka which are the village with no drinking water source. Although such a mechanism provides an unlimited scope for seeking the information about the context (feature space) in various permutation and combinations, it cannot be qualified as SDSS because:

  • It provides only descriptive answers.
  • It does not have any provision for adaptation of decision-maker’s knowledge.
  • Objectives and analysis logic remains in the mind of user (decision-maker).
  • Analysis logic may or may not always be articulatable in form of a series of what lies and where lies queries

An ideal Decision Support System facilitates answers to What if questions based on pre-defined objectives and a set of decision rules. It is prescriptive rather than just a descriptive Query System

Components of SDSS
There are five key components in a SDSS, which differ quite considerably from a GIS. These are:

  • Data base Management
  • Analysis logic (objectives, constraints, decision rules)
  • Spatial display
  • Report generation
  • User’s interface.

Whereas a GIS offers the above functionality as loosely coupled set of tools or primitives, in SDSS all these functionalities appear to be a seamless entity.

Data Base Management
GIS supports spatial query and display of results in as they exist in the data base form. SDSS supports a mix of query, analytical modeling and display of results geared towards the decision making issues, integrating a variety of data sets. i.e. locational, topologic and thematic. SDSS also permits a user to construct and exploit complex spatial relations between all three types of data.

Analytical Procedures
Whereas a GIS offers generic analytical functions as applied to wider spatial applications, SDSS focuses on problem specific in-built analysis models which may be realized using a combination of GIS tools. Analysis models could incorporate objectives, constraints and decision rules. These may in turn be expressed in the form of mathematical equations, expressions (arithmetic/logical) and/or if then-else logic.

Graphic and tabular reports
SDSS facilitates generation of customized graphic and tabular outputs, which suit a particular decision making context, more importantly, during the interactive, interactive and participative session. A GIS on the other hand provides generic tools for generating these reports.

User Interface
User interface of an SDSS has to comply with the requirement of interactive, iterative and participative involvement of a decision-maker. A decision-maker, who could be an expert in his sphere of activity, need not always be a GIS expert. The system should provide an interface which

  • Is easy to use in order to be effective.
  • Should communication systems capability Via ICONS.
  • Should facilitate selection of parameters, data output etc. easily and without forcing a user to refer documents.
  • Should be transparent to facilitate visualization of process represented within the analysis model.

A Prototype (SDSS) for Development Planning at District/Taluka Level
An interactive and Spatial Decision Support System (SDSS) has been developed for development planning at District/ Taluka level. The system provides an easy user interface with menu based in point and shootmode and facilitates transparent where and what with regard to database elements. The system thus realized, using state of the art GIS, consists of three major components viz. database, spatial query shell and spatial decision support shell.

Database has integrated spatial/non-spatial data elements comprising of the thematic map inputs from remote sensing (landuse/landcover, hydrogeomorphology, groundwater prospect) and conventional sources (soil, elevation slope aspect, drainage transport network, village/taluk boundaries, settlement locations) and village-wise non-spatial data on socio-economic and infrastructure aspects like demography, occupation and basic amenities. The database is designed and organized in a manner it minimizes the data redundancy and maximizes the multiplicity of usage of each data element. The majority of the spatial elements in the database are created and being used by the resources analysts.

Spatial query shell
Provides an easy to use, menu based access mechanism in point and shootmode for making integrated query on all aspects (i.e. natural resources, socio-economic and infrastructure) in a single environment. It offers appropriate menus, graphic screens and icons to a user for specifying query in various modes like what lies here, where lies this, theme surface, criterion surface, reference, spatial window and planning sector. The shell also presents different user (spatial and functional) views of the database in user terminology, provides an illusion of seamlessness on the horizontal spread of the data based contents and keeps a user free about where and what of the data base element in the computer storage. An example query could be for tribal pockets (criterion surface) in santrampur taluk, (spatial window) show the groundwater prospects (surface theme) and the villages which do not have drinking water source (where lies this).

Spatial Decision Support Shell
(SDSS) provides what if analysis for different planning issues in an interactive, visual, iterative and spatial environment. Currently it addresses two specific planning problems.

  • For planning the optimum location of village amenities under Minimum Needs Program (MNP).
  • For panning the sustainable land development actions, keeping in view the physical, natural, environmental and socio-economic characteristics of the planning area.

Planning the Location of Village Amenities
In this context the system can be useful for addressing two major issues for providing decision support on the location of additional amenities. In the long run it can be used to prepare a perspective plan depicting the settlements where the additional amenities needs to be located. In the short term, given the resources for specified number of units of an amenity, the system can be used to decide upon the settlements where these units should be located.

The system facilitates evaluation of various options and thereby helps in converging to an optimum set of settlement(s) for locating the additional amenities in an interactive, visual, iterative and spatial environment. At every iteration, the system facilitates:

  • Addition and/or deletion of new locations.
  • quantitative evaluation/examination of the impact of these options with respect to predefined objective function (weighted average distance) and Planning Commission norms (viz. distance and population served)
  • Spatial evaluation/examination in terms of centrewise consumer settlements (within and outside distance norms etc.).
  • Spatial verification of the options against the backdrop of various natural resources, socio-economic and infrastructure conditions in the planning area. These conditions can be queried and overlaid in a variety of forms like where lies this, what lies here and surface theme, etc.

Planning the sustainable land development actions
In this context, the system can be used to arrive at set of optimum land development prescriptions keeping in view the physical, natural, environmental and socio-economic characteristics of the planning area. It operates on a pre-captured land development criterion based on four parameters representing the physical, natural and environmental conditions. These include:

  • Current Landuse/ Landcover
  • Slope
  • Soil Characteristics including Soil texture and Soil Depth
  • Ground water Prospects derived from Hydrogeomorphology

The criterion is built-up and applied on a spatial layer derived on composite of the four basic layers. All possible permutations and combinations of the four parameters are pre-captured into a criterion matrix. This matrix is linked to a composite spatial layer of land parcels. Each of the parameter combination has a pre-assigned a land development prescription based on expert domain knowledge. The overall land development plan is presented spatially. In addition to preparation of the plan based on default criterion, the system facilitates interactive and on the fly modification of the development plan bY

  • Modifying the criterion based on locale specific requirements
  • Examining the plan against various socio-economic and infrastructure related conditions and thereby making the plan more realistic.

The system also provides a mechanism for evaluating the impact of proposed development actions. Currently the impact can be examined in terms of cost and manpower requirements based on per unit area assumptions for each development action. This however, can be extended to aspects like environment impact, provided the impact can be modeled in form of mathematical equations.

The presented framework for Spatial Decision Support Systems has been adopted for facilitating Spatial Decision Support at District/ Taluka level. This was an attempt to realize decision support system facilitating (simulating) the what if scenarios for two different planning contexts covering Natural resources and Infrastructure planning. The most important aspect was the characterization or modeling of the impact and customization of the GIS tools to realize such a system. The approach, thus presented, can be very successfully adopted for a vide spectrum of planning and decision support problems in spatial context.

Author wishes to thank Shri A K S Gopalan, Director, SAC and Shri A R Dasgupta, Dy. Director, SAC for guidance and support.


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