GIS & Databases Ming-Chun Lee

Data vs. Information Data: raw fact Information: data processed to reveal meaning Database system transforms data into information through queries

Data vs. Database Database is a collection of related data Database stores data in an organized manner Database exists, first and the foremost, to serve users’ requirements

Data Modeling From GIS perspective, database is the “physical” form of data representation Describe the reality in terms of different concepts to either physical objects, such as a house, a parcel, or social/political meanings, such as land uses, zoning codes, postal zip codes. In the GIS representation, GIS needs to know the logic behind all the visual graphical elements on either a computer display or a map. A polygon representing a house has to be fully within another polygon representing a parcel.

Data Modeling Conceptual Model - How humans see the world Users’ view of the world (interpreted by data) Logical Model - How programs see the world Precise definition of the set of objects of interest to identify the relationships between them including such relationships as “located at”, “owned by”, “is part of” Physical Model - How machines see the world Implementation of data model within the framework of relational database technology

Object Relationships One-to-One One-to-Many Many-to-One Many-to-Many

Types of Databases Flat File Hierarchical Relational Single Table; No Relationships Hierarchical Nested Tables One-to-One & One-to-Many Relationships Relational Interrelated Tables One-to-One, One-to-Many, Many-to-One, Many-to-Many Relationships

Flat File Database ID Route Timepoint 1 Timepoint 2 … Timepoint 10 1 71 4th Ave. S & S Washington St. 5th Ave. S & S Jackson St. 50th Ave. NE & NE 75th St. 2 72 Ravenna Ave. NE & NE 80th St. 3 73 15th Ave. NE & NE 125th St.

Hierarchical Database TPID Timepoint 1 4th Ave. S & S Washington St. 2 5th Ave. S & S Jackson St. … 10 50th Ave. NE & NE 75th St. ID Route 1 71 2 72 3 73 TPID Timepoint 1 4th Ave. S & S Washington St. 2 5th Ave. S & S Jackson St. … 10 50th Ave. NE & NE 75th St. TPID Timepoint 1 4th Ave. S & S Washington St. 2 5th Ave. S & S Jackson St. … 10 15th Ave. NE & NE 125th St.

Relational Database ID Route 1 71 2 72 3 73 OID Route TP Order 101 71 102 2 110 10 201 72 202 210 301 73 302 310 TPID Timepoint 1 4th Ave. S & S Washington St. 2 5th Ave. S & S Jackson St. … 110 50th Ave. NE & NE 75th St. 210 Ravenna Ave. NE & NE 80th St. 310 15th Ave. NE & NE 125th St.

Relational Database Concepts One Table for Each Type of “Thing/Entity” Within a Table: One Row for Each Distinct “Thing” of that Type Primary Key: A Unique Identifier for the distinct “Thing” Foreign Key: A Reference to Another Table’s Primary Key

GIS as a Relational Database Join Tables to Spatial Data Layers User ID Name Abbrev. 10 Washington WA 12 Oregon OR 18 Michigan MI ID Area Perimeter User ID 1 25.3 10.4 10 2 30.2 13.5 12 3 10.1 8.2 18 4 27.8 12.6

Object-oriented Database The idea of "object-oriented" database is to organize information into the sorts of “objects" that people recognize. Instead of "decomposing" each feature in a distinctive list of attributes, features are stored as collections of attributes and behaviors. A class is a computer construct representing a concept bound in a cohesive package Some are concrete (i.e. real world) Bank account Rental item Database item Pile Others are abstract Scanner Stream Math An Object: An instance of a CLASS Contains meaningful data Concepts that occupy memory space at runtime are, according to the definition, objects

Object-oriented Databases Feature Object Relationship

Object-oriented Database It enables you to make the features in GIS datasets smarter by endowing them with natural behaviors and relationship among features. It brings a physical model closer to its logical model. The users work with objects of interests such as roads, lakes and transformers.

Features, Objects, and Relationships

Object-oriented Relational Databases ArcGIS uses a geographic data model that represents spatial information as objects, features, raster, and other data types. It integrates two GIS data models, the traditional relational database model and an object-oriented relational model called a geodatabase All persistent (database) information is still in tables, but some of the tabular entries can have richer data structure

Object-oriented Relational Databases All database information is still in tables, but some of the tabular entries can have richer data structure

GIS architecture Built upon relational database Spatial/non-spatial data are stored in tables Storing spatial data in table is tedious Built upon object-oriented database Can define user-defined data type (e.g. ArcGIS geodatabase has different data models such as hydrology, network, land parcel, and so on)