Design of a Spatial system is like any other Enterprise application ... subject that
the table represents”. Database Design for Mere Mortals by Michael Hernandez ...
Database Design Concepts and Data Integration URISA February 9th, 2005 Bob Earle 3/10/2005
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Agenda • A few Design tips and guidelines, some of which I learned the hard way • Many GIS staff get database design and maintenance thrust upon them • The ‘r’evolution of GIS at Sacramento County; how we became a data integrator, but not necessarily by plan
Design of a Spatial system is like any other Enterprise application
Earlier is Better
Translation of User Requirements
•Business Rules •Model the User’s View
Entity Relationship Diagram
Æ Good design tool, good communication tool
Access ERD (Relationships)
You may already have an ERD tool and not know it
UML
May look complicated, but at its heart is the ERD
Sacramento County ERD
Normalization Remove Repeating Groups Every non-key column must be dependent on all parts of the primary key No non-key column may be functionally dependent on another non-key column
Introduced by E.F. Codd
“Every attribute will refer to the Primary key, the whole key and nothing but the key, so help me Codd” A table should have a field that uniquely identifies each of its records, and each field in the table should describe the subject that the table represents” Database Design for Mere Mortals by Michael Hernandez
Database Data Models
Metadata
Database Design Fallacies • Design your system to replicate existing practices • You can throw your data model away when you have implemented your database • I will just put it in a “note” • Metadata is too much trouble • My spreadsheet is good enough • GIS shouldn’t be putting its nose into everybody’s business
More Database Design Fallacies • Nobody will ever need my data • Just import your shapefiles into SDE and voila… you have a Geodatabase • Normalized data is fast performing data • Spatial data is just data
Database Design Truths • • • •
Spatial data is just data Design on paper, then a computer Earlier is better Document deviances from the conceptual design
More Database Design Truths • • • •
Use meaningful attribute and table names Flag for deletion, rather than delete Take the user’s key away Use database constraints, rather than coded business rules
What is so Special about Spatial Data? • How it is the same than “regular” data – Data relationships – Integrity – Key Asset
• How it is different – – – – –
Spatial Key (Location is a type of key) Topology Heavy load Long transaction Advanced data type
Database
Early GIS
Community GIS
Evolution of the spatial data model Ian McCarg “Design With Nature”
ArcInfo Coverages
Oracle Spatial ArcStorm SDE GeoDatabase Shape File
True TrueSpatially Spatially Enabled Enabled Database Database
GIS Layers •Points •Lines •Polygons •Surfaces
3D
Scanned Maps
Scanned Documents
Attribute Data
Orthophotography
Levels of Data Integration
If it were a perfect (GIS) World Spa
Transactions
Do
rne e t n I
tial
n ts e cum
Universal Database
t
Regional
Dep
artm enta
l
I can’t say it was easy, but I can say it was worth it!!
Sacramento County Property Systems (Without data sharing)
SAP/ COMPASS (Oracle)
PDB Application (Mainframe)
GHB/GAX Applications (Mainframe)
APS Permits system (Oracle) CPS Unsecured Tax Application (Oracle)
GIS (ESRI)
Utility Billing/ CUBS (SAP?,Oracle?)
Planning
Public Works Direct Levy Maintenance Application
Sacramento County Property Systems
SAP/ COMPASS (Oracle)
PDB Application (Mainframe)
GHB/GAX Applications (Mainframe)
APS Permits system (Oracle) County-wide Shared Property Data Warehouse
CPS Unsecured Tax Application (Oracle)
GIS (ESRI)
Utility Billing/ CUBS (SAP?,Oracle?)
Planning
Public Works Direct Levy Maintenance Application
Examples of Shared Data Benefits • • • •
Tax Rate Areas Vineyards Utility Billing Minimize data redundancy and costs in the Regional Cooperative
Data Ownership, Dissemination, and Accessibility Policies • Ownership - Departments own their data, GIS is the middleman • Dissemination - Open Access, Cooperative Mapping based on Standards • Access - Concerns over safety
Database Architecture Transactional
Transactional
Warehouse
Warehouse
Shared
Shared Firewall
Summary - Benefits of Good Design • Data integrity • Flexibility in data retrieval and analysis • Follows business rules and therefore supports organizational requirements • Easier to share data • Different users access same data • Accommodates different views of the data • Minimal Data Redundancy • Breaks out of Spreadsheet mentality
Questions, Comments?
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