Page 116 - DCAP208_Management Support Systems

Unit 7: Business Analytics and Data Visualization

Attribute data is wrong or incomplete: Often the attribute data does not match exactly Notes
with the spatial data. This is because they are frequently from independent sources and
often different time periods. Missing data records or too many data records are the most
common problems.

7.4.2 Data Storage, Editing and Retrieval Subsystem

The second necessary component for a GIS is the data storage and retrieval subsystem. The Data
Storage and retrieval subsystem organizes the data, spatial and attribute, in a form, which
permits it to be quickly retrieved by the user for analysis, and permits rapid and accurate
updates to be made to the database. This component usually involves use of a database
management system (DBMS) for maintaining attribute data. Spatial data is usually encoded and
maintained in a proprietary file format.

Organizing Data for Analysis

Most GIS software organizes spatial data in a thematic approach that categorizes data in vertical
layers. The definition of layers is fully dependent on the organization’s requirements.

Typical layers used in natural resource management agencies or companies include forest cover,
soil classification, elevation, road network (access), ecological areas, hydrology, etc.

Editing and Updating of Data

Perhaps the primary function in the data storage and retrieval subsystem involves the editing
and updating of data. Frequently, the following data editing capabilities are required:

Interactive editing of spatial data
Interactive editing of attribute data

The ability to add, manipulate, modify, and delete both spatial features and attributes
(independently or simultaneously)
Ability to edit selected features in a batch-processing mode.

Data Retrieval and Querying

The ability to retrieve data is based on the unique structure of the DBMS and command interfaces
are commonly provided with the software. Most GIS software also provides a programming
subroutine library, or macro language, so the user can write their own specific data retrieval
routines if required.
Querying is the capability to retrieve data, usually a data subset, based on some user-defined
formula. These data subsets are often referred to as logical views. Often the querying is closely
linked to the data manipulation and analysis subsystem. Querying can be either by example of
by content.

7.4.3 Data Manipulation and Analysis Subsystem

The Data Manipulation and Analysis subsystem allows the user to define and execute spatial and
attribute procedures to generate derived information. This subsystem is commonly thought of
as the heart of a GIS, and usually distinguishes it from other database information systems and
Computer-Aided Drafting (CAD) systems.

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