Data refers to the Earth's features and resources, as well as human activities based on or related to those features and resources. Data is collected and used to solve problems and make decisions related to geography, i.e. location, distribution and spatial relations within a certain geographical framework. Geographic data differs from other types of data in that it is geographically specified.
GIS emphasizes the use of the spatial dimension for converting data into information. The value of an attribute can be in the form of a number, a character string, a date, or a logical expression. An array is a collection of data items of the same size and type (although they may have different values).
The use of database represents a change in the perception of data, the way of data processing and the purposes of data use, instead of the physical storage of data. Network data is organized by records which are classified into record types, with 1:n pointers linking associated records. The method of representing geographic features with the basic graphical elements of points, lines and polygons is said to be the vector method or vector data model, and the data is called vector data.
Related vector data is always organized by theme, also called layers or opacities. The data can be divided into tiles for easier management. A tile is uniquely identified by a file name. The vector method is based on the concept that the features can be identified as separate entities or objects; this method is therefore based on the object representation of the real world (Goodchild, 1992).
The method of representing geographic features by pixels is called the raster method or raster data model, and the data is described as raster data. A raster pixel represents the generalized characteristics of an area of specific size on or near the Earth's surface. The actual land size depicted by a pixel depends on the resolution of the data.
Interval - an ordinal scale with ordering based on numerical values written according to an arbitrary date. Categorical relationships based on classification are hierarchical or taxonomic in nature, meaning that data are organized into progressively different levels of detail. A data file can be accessed on a computer system by specifying a path consisting of the device name, one or more directory names, and the file's own name.
The workspace concept used by many geographic information system software packages is based on the directory structure of the host computer.
D ATA – F UNDAMENTAL C ONCEPTS
Non-spatial data (also called attribute or characteristic data) is the information that is independent of any geometric considerations. Standard database systems do not allow links between objects of the same record type (class). The integrity rules for geographic data are too complex, e.g. the arcs forming a polygon must be connected to form a complete boundary.
The DBMS handles many functions that would otherwise have to be programmed into the GIS. Any DBMS makes assumptions about the data it handles, and to make effective use of a DBMS it is necessary to fit those assumptions. Total DBMS solution: All data is accessed through the DBMS, so it must fit the assumptions imposed by the DBMS designer.
Mixed solution: Some data (typically attribute tables and . relationships) are accessed through the DBMS because they fit the model well, while some data (typically locational) are. It is a property of transactions that if they are aborted before they complete, the database will be restored to a self-consistent state, usually that before the transaction began. A DBMS is like a full-service bank, providing many features and services that are missing from a relatively spartan repository.
A data definition language (DDL) is used to specify what data will be stored in the database and how it is related. A data manipulation language (DML) is used to add, retrieve, update, and delete data in the DBMS. A major benefit we get from following a data model stems from the model's theoretical foundation.
The theory shows the power of analysis, the ability to extract inferences and to create inferences that emerge from the raw data. Conceptual: This is the expression of the database designer's model of the real world in the language of the data model. Logical (User View): Different user groups can be given access to different parts of the database.
D ATA M ODELLING
It is sometimes called a semantic data modeling method because it used a human language-like vocabulary to describe. Logical data modeling is a comprehensive process of consolidating and refining the conceptual data model. The proposed database is assessed in its entirety to identify potential issues such as;
It is developed by mapping the conceptual data model (such as the E-R diagram) into a software-dependent design document. It is also known variably as a data dictionary, item definition table, specific data table, or physical database definition. It's both software- and hardware-specific, meaning that physical schematics for different systems look different from each other.
Process modeling is the process-oriented approach, as opposed to the data-oriented approach, of information system design. In the context of information system design, process modeling is one of the methods of structured business function decomposition used to determine user requirements in conceptual modeling.
