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Spatial Database
GISC 6383 Fall 2005
Bryan Dennie
Jian Huang
Jianghong Li
Judy Mays
Table of Contents
1. Introduction
2. Comparison Criteria
a. Overview, Cost, and Standards
b. GIS Application
c. Spatial Data Types
d. Query
e. Data loading
f. Other Criteria (Compatibility with GIS Applications,
Server Capability, Stand-Alone or part of System)
3. Summary
4. Appendix I: Oracle Spatial Functions
5. Appendix II: IBM DB2 Spatial Functions
6. References
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Introduction
At the request of the Retail Manager, the option of performing new store location
assessment in-house is being investigated. In order to evaluate prospective locations this
company, DFW Stores, Inc., needs to incorporate spatial data to its database systems.
Our committee has researched several options and presents the results in this report.
Locational data may be integrated with business data by adding spatial capabilities to the
database system. Querying and analyzing spatial data requires specialized data types and
functions that are provided by the spatial database. Points, lines, and polygons are used
to model geographic entities and are referenced to a specific location by means of
coordinates such as latitude and longitude. Not only can spatial objects be referenced to
each other, but this spatial data may then be related to other conventional business and
demographic data within the database. Queries may then be made on this combined data
and results viewed in database report format or in map form by means of a visualization
tool.
The potential spatial databases considered for this project are: IBM DB2 Spatial Extender
and Oracle Spatial, both industry-leading database providers; PostGIS, an open-source
database that includes some spatial functionality; and ArcSDE, a spatial data engine from
ESRI, the market leader in GIS applications. Following is a general introduction that
provides an overview of each system.
Once a separate extension to IBM DB2 database, Spatial Extender is now integrated
within current versions of the database. Spatial information, in formats such as points,
lines, and polygons, can be analyzed, generated, stored, accessed, and queried within the
spatial database.
Oracle Spatial, a paid extension to Oracle Enterprise Edition, offers the possibility to
store, update, retrieve and analyze spatial data in and from the database. Central data
management is made possible by storing both spatial and traditional data in the same
location.
PostGIS adds geographic object support to the open-source object-relational database,
PostgreSQL. In other words, PostGIS enables PostgreSQL to store, relate, join, query,
analyze with spatial data inside the database.
ArcSDE is not an extension to a database, but rather middleware, or a server software
product. ArcSDE augments the range of data types to include spatial data that can be
managed in traditional relational databases like IBM DB2, Oracle, or Microsoft SQL
Server. It is the necessary connection for ESRI’s ArcGIS systems, acting as a conduit to
applications that perform geographic or spatial analysis as it serves data to users within
an organization or to the internet.
In the next section, the following topics are used for comparison: cost, standards, GIS
applications, spatial data types supported, database queries, spatial functions, data
loading, compatibility with GIS applications, and server capability.
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1. Cost and Standards:
Spatial Database
Product
IBM DB2 spatial
extender
ArcSDE
Oracle Spatial
Cost
Standards
For earlier versions of DB2, cost to add
SpatialExtender is $9,250
Conforms to the ISO SQL/MM Spatial
Standard and the OpenGIS Consortium's
(OGC's) Simple Feature Specification for
SQL
Now included in DB2v8.1 & higher:
IBM DB2 Personal Edition $461
IBM DB2 cost varies with number of
licenses:
Express Edition $4,874
Enterprise Server Edition $33,125
Starting price is $10,000 for commercial
applications.
ArcSDE supports OpenGIS simple features
and SQL statements.
Enterprise Edition:
 Named user license: $800
 Processor license: $40,000
Oracle spatial implements the OpenGIS
Consortium Simple Features guidelines.
Oracle is also committed to supporting the
new OGC Geographic Markup Language
(GML) as well as Open Location Service
interfaces.
Oracle Spatial:
 Named user license: $200
 Processor license: $10,000
PostgreSQL /
PostGIS
Refractions Research under the GNU
General Public License developed PostGIS
for open source, free to the public
distribution. It and the PostgreSQL database
are completely open-source and can be easily
downloaded over the internet for free.
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Version 1.0 of PostGIS is currently under
validation of the Open GIS Consortium
“Simple Features Specification for SQL”
which defines standard GIS object types,
the functions required to manipulate them,
and a set of metadata tables.
2. GIS Application
Spatial Database
Product
IBM DB2
Spatial Extender
GIS Application
In 2001 IBM and ESRI partnered and jointly developed the IBM DB2 Spatial Extender,
which incorporated geographic or spatial information with business and other data already
residing in an IBM Universal Database. Spatial data may be manipulated within the
database by utilizing spatial extender functions to return GIS information in tabular format.
A separate visualization tool is needed to see a graphic representation such as a map.
ArcSDE is a server software product used to access massively large multiuser geographic
databases stored in relational database management systems (RDBMSs).
ArcSDE
It is an integrated part of ArcGIS and a core element of any enterprise GIS solution. Its
primary role is to act as the GIS gateway to spatial data stored in a RDBMS.
ArcSDE provides a suite of services that enhance data management performance, extend
the range of data types that can be stored in a RDBMS, enable schema portability between
RDBMSs, and offer configuration flexibility.
Oracle Spatial
PostgreSQL /
PostGIS
Oracle Spatial is an extension to Oracle9i that provides geometry storage, indexing, and
spatial search functions. When used with Oracle9i Enterprise Edition, Oracle Spatial
provides a standards-based data management solution for the delivery of GIS, Internet
mapping, and mobile location-based services. It serves as a technology platform for
managing an enterprise-wide GIS or location-enabled e-business applications.
The software itself is a limited standalone GIS, but there are other open source applications
that can be downloaded to enhance it’s GIS capabilities.
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3. Spatial Data Types:
Spatial Database
Product
IBM DB2 Spatial
Extender
Spatial Data Type
Graphic
 Points
 Lines
 Polygons
Ability to “subtype” these basic
types
Support all the ESRI
geometry types
ArcSDE
SDO_GEOMETRY – can support
three geometric primitive types:
Geometric
Geometric Types
Types
Point
Oracle Spatial
PostgreSQL /
PostGIS


Points.

Polygons




Line string
Arc line
string
Compound
line string
SelfSelf-crossing
line strings
Valid
Line Strings (can be linear,
curved or both)
Polygon
Polygon
with hole
Compound
polygon
Optimized
polygons
SelfSelf-crossing
polygons
Not valid
Point, Multipoint
Line, Multiline
Polygon,,Multipolygon,
Geometrycollections
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4. Query:
Spatial Database
Product
Query
Functions
80 built-in spatial data functions
IBM DB2 Spatial
Extender


SQL access to spatial data
SQL querying of spatial data
and/or joining of spatial data
with conventional database or
business data
8 geometry type constructor functions
12 spatial data comparison functions
20 geometric conversion functions
40 geometric calculator functions
Examples:
ST_LineString, ST_Intersects, ST_AsShape, ST_Area
ArcSDE
The spatial query in ArcSDE and
RDBMS client is implemented in
the form of SQL statements.
Requests for data occur when
actions like zooming in/out,
querying rows in table, and
displaying tabular or spatial data
are performed. These types of
requests are translated into SQL
statements and passed to the
RDBMS for processing.
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All functions depend on the ArcGIS
software, such as ArcMap
Cont’d 4. Query
Spatial Database
Product
Query
Functions
Oracle Spatial uses a two-tier
process for querying spatial data.
Over 400 spatial functions, Oracle Spatial includes
functions for length/area calculations, buffer, centroid,
convexhull, geometry intersection, union. list the
major functions:


Oracle Spatial
The first part of the query
selects candidate rows based
only on their spatial index.
The second step of the query
looks at each candidate and
determines if it meets the
query exactly.
This two-tier approach allows for
quick querying by leveraging the
spatial indexes.
3 SDO_GEOMETRY object type method
17spatial operators
21 Geometry Function
5 Spatial Aggregate Functions
3 Coordinate System Transformation Functions
40 Linear Referencing Functions
6 Migration Procedures
11 Tuning Functions and Procedures
2 Utility Functions
Management Functions
AddGeometryColumn, DropGeometryColumn,
SetSRID
PostgreSQL /
PostGIS
Spatial queries are performed the
same way they are constructed in
any other database query.
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Relate Functions
Distance, Equals, Disjoint, Intersects, Touches,
Crosses, Within, Overlaps, Contains, Intersects,
Relate
Processing Functions
Centroid, Area, Length, PointOnSurface, Boundary,
Buffer, ConvexHull, Intersection, Difference,
GeomUnion, Envelope, IsSimple, IsClosed, IsRing,
NumPoints,
ExteriorRing,
NumInteriorRings,
EndPoint, StartPoint, GeometryType, X, Y, & Z.
5. Data loading:
Spatial Database
Product
IBM DB2 spatial
extender
Data Loading
Spatial data may be imported into and exported from Spatial Extender through data
exchange files. Two types are supported:
 shapefiles and ESRI SDE transfer files.
 Also supported are industry standard data types: Well Known Binary (OGC WKB)
andd Well Known Text (OGC WKT)

ArcSDE

Oracle Spatial


Raster data: ArcSDE supports the following formats: ERDAS IMAGINE, ERDAS(.lan
& .gis), ERDAS Raw, GIF, BIL/BIP/BSQ, BMP, MrSID compressed images, JPEG,
ADRG, PNG, ER Mapper, CIB, CADRG.
Vector data: shape file, AutoCAD, coverage, tab file for MapInfo etc.
Writing SQL statement to create table & load data into the table directly.
Convert Shape to SDO
1. Using shp2sdo to create load assistant files
2. Using sqlplus to create table
3. Using sqlldr to load the actual data into the table
Other data formats should be converted into shapefile before loading.
PostgreSQL /
PostGIS
Loading data can be done two ways.
 The first way is using the loader, which converts ESRI Shape files into SQL suitable
for loading in PostGIS/PostgreSQL. This is similar to importing data into an ESRI
Geodatabase.
 The other way to get data into the database are converting the data to a text
representation, then use traditional SQL data loading statements.
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6. Other Criteria
Spatial Database
Product
Compatibility with
GIS applications
Server Capability
Stand-alone or part
of DB system?
IBM DB2 spatial
extender
Supports visualization tools
such as ESRI's ArcView
GIS, ArcExplorer, ArcInfo,
ArcView BusinessAnalyst as
well as other vendors such as
MapInfo.
To view graphic or map
representation,
a
visualization tool must be
used.
If deployed within
DB2
edition
with
server
capabilities then it can.
IBM
recommends
an
architecture
utilitizing
ESRI’s
ArcSDE
for
distributed computing.
DB2
Spatial
Extender
resides in IBM’s DB2
Universal Database
Since ArcSDE if a part of
ESRI GIS software fimaly, it
supports all ESRI GIS
software. At the same time, it
support
AutoCAD
by
Autodesk.
Serves spatial data to ArcGIS
Desktop
(ArcReader,
ArcView, ArcEditor, and
ArcInfo), to Internet clients
through ArcIMS, and to
applications developed with
ArcGIS Engine and ArcGIS
Server.
No, ArcSDE is only a
gateway
connected
RDBMS to Client or GIS
application
Oracle Spatial is an option
for Oracle Enterprise Edition
that
provides
advanced
spatial features to support
high-end GIS and LBS
solutions.
Integration with Oracle9i
Application Server
Oracle Spatial is supported
on Oracle Enterprise
Edition.
Available GIS applications
that can run PostGIS are
uDig (User-friendly Desktop
Internet
GIS)
and
MapServer.
Both are
internet-web applications that
can create, acquire, view, and
modify spatial data.
PostgreSQL, an open source,
object-relational
database
that is used in conjunction
with PostGIS acts as the
server.
It is capable of
running on Windows, Linux,
and Unix operating systems.
PostGIS is a downloadable
software that spatially
extends PostgreSQL.
ArcSDE
Oracle Spatial
PostgreSQL /
PostGIS
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Summary
In order for DFW Stores, Inc. to evaluate retail site selection in-house, we need a spatial
database to store/retrieve spatial data and enhance the company’s future. The main
feature that we could use the spatial database for is deciding where to build/close down
stores on the basis of costs, statistics, proximity of competitors, and potential clientele.
Some functions that would be useful for our company are as follows:




View extent of sales area (buffer) and
determine which customers live inside and
outside of this area (geocode) or if the
location of the store does not fully support
customers in the area (centroid).
Determine nearest location from “model
customers” via census tract data to nearest
store (distance).
Ensure that new store sites do not interfere
with other stores customers (overlap,
contains, etc…).
Model non-producing stores with all
available spatial data (customers, site
Figure 1: Retail selection based on customers
location, competitor location, census bureau
and proximity to competitors.
information, etc…) to determine why they
do not produce so that the business model can be enhanced.
Criteria used in the selection for the spatial database are the following:
 Cost
 Standards met
 GIS application
 Spatial data types supported
 Queries from the database
 Spatial functions
 Data loading
 Compatibility with other GIS applications
 Server capability
 Ability to be stand alone or integration with database
While there are several databases and options that could have been used for this
comparison, only the following spatial databases were reviewed:




ArcSDE—spatial data engine from ESRI, the market leader in GIS applications.
PostGIS—open source database and downloadable spatial extension
IBM DB2 Spatial Extender—major database vendor with own spatial extension
Oracle Spatial—database market share leader with own spatial extension
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PostGIS
Despite the fact that PostGIS is absolutely free, it is hard to recommend it. As the saying
goes ‘you get what you pay for’, and because of this fear, “in the spatial industry, open
source freeware has a barely measurable market share compared with the proprietary
products sold by … other geospatial vendors.” [9] Because of the limited market share,
there are very few people that would be available for consulting/support in the event it
was needed. Also, PostGIS is totally funded by Refractions Research and some “small
time” consultant companies/vendors, and it has no major corporate support. There seems
to be a high risk with longevity with this product.
ArcSDE
Built by the leading GIS vendor in the nation ESRI, it (ArcSDE) has little/no
functionality by itself. This option requires the purchase of a qualified RDBMS ($30k $40k), ArcSDE ($10k), and then ArcGIS Desktop (another $5k) in order to get the
complete functionality of the system. The total is approximately $45,000-$55,000.
Granted, if this system were implemented, you would have one of the most capable and
desirable Geographic Information Systems, but for our purposes, it is overkill.
Oracle Spatial
This selection is quite capable of handling the needs of this company. The functions that
are built into it are exactly what this company is looking for. Also, it has been the
leading database vendor for a long time, and has many followers. There is ample support
available and plenty of consultants that would be available for hire if needed. However,
the price for a single processor license of the Enterprise Oracle Database is $40k and one
for Oracle spatial is $10k, which comes to a combined total of $50,000. If we were
willing to buy this, then we should just go with ArcSDE and a non-Oracle Database.
IBM DB2 Spatial Extender
Very similar to Oracle Spatial, it has all the spatial functionality needed for our company.
The IBM DB2 is the second leading vendor for RDBMS, so there are plenty of
consultants available if needed. The ability to visually display the data in ArcExplorer
(free by download from ESRI’s website) assisted in this decision. All created data can be
stored in shape files for distributing data with other companies. Also, since the company
will need to purchase a database for the storage of this system, it will be provided for free
with the new purchase of the Enterprise Server Edition of the IBM DB2 database. The
total cost for this spatial database will be ~$30,000. (This is $20,000 less than the Oracle
Spatial and $15,000 less than the ArcSDE systems.)
Recommendation
The recommendation from this group is to use IBM DB2 Spatial Extender. It has the
same functionality of Oracle Spatial, while being $20,000 less. It does not have the
functionality of the ArcSDE system, but it is also $15,000 less. And, in the event we ever
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wanted all of the functionality of ArcSDE, then we could purchase it and update the
database at that time.
Appendix I: Functions for use with Oracle Spatial
Over 400 spatial functions, Oracle Spatial includes functions for length/area calculations, buffer, centroid, convexhull,
geometry intersection, union. list the major functions:
1. SQL Statements for Indexing Spatial Data
ALTER INDEX
ALTER INDEX REBUILD
ALTER INDEX RENAME TO
CREATE INDEX
DROP INDEX
2. SDO_GEOMETRY Object Type Methods
GET_DIMS
GET_GTYPE
GET_LRS_DIM
10 Spatial Operators
SDO_FILTER
SDO_NN
SDO_NN_DISTANCE
SDO_RELATE
SDO_WITHIN_DISTANCE
3. Geometry Functions
SDO_GEOM.RELATE
SDO_GEOM.SDO_ARC_DENSIFY
SDO_GEOM.SDO_AREA
SDO_GEOM.SDO_BUFFER
SDO_GEOM.SDO_CENTROID
SDO_GEOM.SDO_CONVEXHULL
SDO_GEOM.SDO_DIFFERENCE
SDO_GEOM.SDO_DISTANCE
SDO_GEOM.SDO_INTERSECTION
SDO_GEOM.SDO_LENGTH
SDO_GEOM.SDO_MAX_MBR_ORDINATE
SDO_GEOM.SDO_MBR
SDO_GEOM.SDO_MIN_MBR_ORDINATE
SDO_GEOM.SDO_POINTONSURFACE
SDO_GEOM.SDO_UNION
SDO_GEOM.SDO_XOR
SDO_GEOM.VALIDATE_GEOMETRY
SDO_GEOM.VALIDATE_GEOMETRY_WITH_CO
NTEXT
SDO_GEOM.VALIDATE_LAYER
SDO_GEOM.VALIDATE_LAYER_WITH_CONTE
XT
SDO_GEOM.WITHIN_DISTANCE
4. Spatial Aggregate Functions
SDO_AGGR_CENTROID
SDO_AGGR_CONVEXHULL
SDO_AGGR_LRS_CONCAT
SDO_AGGR_MBR
SDO_AGGR_UNION
5. Coordinate System Transformation Functions
SDO_CS.TRANSFORM
SDO_CS.TRANSFORM_LAYER
SDO_CS.VIEWPORT_TRANSFORM
6. Linear Referencing Functions
SDO_LRS.CLIP_GEOM_SEGMENT
SDO_LRS.CONCATENATE_GEOM_SEGMENTS
SDO_LRS.CONNECTED_GEOM_SEGMENTS
SDO_LRS.CONVERT_TO_LRS_DIM_ARRAY
SDO_LRS.CONVERT_TO_LRS_GEOM
SDO_LRS.CONVERT_TO_LRS_LAYER
SDO_LRS.CONVERT_TO_STD_DIM_ARRAY
SDO_LRS.CONVERT_TO_STD_GEOM
SDO_LRS.CONVERT_TO_STD_LAYER
SDO_LRS.DEFINE_GEOM_SEGMENT
SDO_LRS.DYNAMIC_SEGMENT
SDO_LRS.FIND_LRS_DIM_POS
SDO_LRS.FIND_MEASURE
SDO_LRS.GEOM_SEGMENT_END_MEASURE
SDO_LRS.GEOM_SEGMENT_END_PT
SDO_LRS.GEOM_SEGMENT_LENGTH
SDO_LRS.GEOM_SEGMENT_START_MEASURE
SDO_LRS.GEOM_SEGMENT_START_PT
SDO_LRS.GET_MEASURE
SDO_LRS.IS_GEOM_SEGMENT_DEFINED
SDO_LRS.IS_MEASURE_DECREASING
SDO_LRS.IS_MEASURE_INCREASING
SDO_LRS.LOCATE_PT
SDO_LRS.MEASURE_RANGE
SDO_LRS.MEASURE_TO_PERCENTAGE
SDO_LRS.OFFSET_GEOM_SEGMENT
SDO_LRS.PERCENTAGE_TO_MEASURE
SDO_LRS.PROJECT_PT
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SDO_LRS.REDEFINE_GEOM_SEGMENT
SDO_LRS.RESET_MEASURE
SDO_LRS.REVERSE_GEOMETRY
SDO_LRS.REVERSE_MEASURE
SDO_LRS.SCALE_GEOM_SEGMENT
SDO_LRS.SET_PT_MEASURE
SDO_LRS.SPLIT_GEOM_SEGMENT
SDO_LRS.TRANSLATE_MEASURE
SDO_LRS.VALID_GEOM_SEGMENT
SDO_LRS.VALID_LRS_PT
SDO_LRS.VALID_MEASURE
SDO_LRS.VALIDATE_LRS_GEOMETRY
7. Migration Procedures
SDO_MIGRATE.FROM_815_TO_81X
SDO_MIGRATE.OGIS_METADATA_FROM
SDO_MIGRATE.OGIS_METADATA_TO
SDO_MIGRATE.TO_734
SDO_MIGRATE.TO_81X
SDO_MIGRATE.TO_CURRENT
8. Tuning Functions and Procedures
SDO_TUNE.ANALYZE_RTREE
SDO_TUNE.AVERAGE_MBR
SDO_TUNE.ESTIMATE_INDEX_PERFORMANCE
SDO_TUNE.ESTIMATE_TILING_LEVEL
SDO_TUNE.ESTIMATE_TILING_TIME
SDO_TUNE.ESTIMATE_TOTAL_NUMTILES
SDO_TUNE.EXTENT_OF
SDO_TUNE.HISTOGRAM_ANALYSIS
SDO_TUNE.MIX_INFO
SDO_TUNE.QUALITY_DEGRADATION
SDO_TUNE.RTREE_QUALITY
9. Utility Functions
SDO_UTIL.EXTRACT
SDO_UTIL.GETVERTICES
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Appendix II: Functions for use with IBM DB2 Spatial Extender
1. Geometry Conversion
ST_AsShape
ST_WKBToSQL
ST_GeomFromWKB
ST_GeomCollFromWKB
ST_PointFromWKB
ST_LineFromWKB
ST_PolyFromWKB
ST_MPointFromWKB
ST_WKTToSQL
ST_PointFromText
ST_AsGML
ST_MLineFromWKB
ST_MPolyFromWKB
ST_LineFromText
ST_PolyFromText
ST_MPointFromText
ST_MLineFromText
ST_MPolyFromText
ST_GeomCollFromTxt
ST_GeomFromText
2. Geometry Constructor
ST_Point
ST_LineString
ST_Polygon
ST_MultiPoint
ST_MultiLineString
ST_MultiPolygon
ST_GeomCollection
ST_Geometry
3. Data types Comparison
ST_Contains
ST_Crosses
ST_Disjoint
ST_EnvIntersects
ST_EqualCoordsys
ST_Equals
ST_EqualSRS
ST_Intersects
ST_MBRIntersects
ST_Overlaps
ST_Relate
ST_Touches
4. Functions for information about dimensions
ST_Area
ST_Dimension
ST_Length
5. Measures and Coordinates for Geometry
ST_CoordDim
ST_IsMeasured
ST_IsValid
ST_Is3D
ST_M
ST_MaxM
ST_MaxX
ST_MaxY
ST_MaxZ
ST_MinM
ST_MinX
ST_MinY
ST_MinZ
ST_X
ST_Y
ST_Z
6. Information about geometries within a geometry.
ST_Centroid
ST_EndPoint
ST_GeometryN
ST_LineStringN
ST_MidPoint
ST_NumGeometries
ST_NumLineStrings
ST_NumPoints
ST_NumPolygons
ST_PointN
ST_PolygonN
ST_StartPoint
7. Information About Boundaries
ST_Boundary
ST_Envelope
ST_EnvIntersects
ST_ExteriorRing
ST_InteriorRingN
ST_MBR
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ST_MBRIntersects
ST_NumInteriorRing
ST_Perimeter
References
ArcSDE
1.
http://www.esri.com/software/arcgis/arcsde/index.html
2.
http://www.gisfusion.com/gis/arcsde.cfm
3.
http://www.esri.com/library/brochures/pdfs/arcsde-server.pdf
IBM DB2 Spatial Extender
4.
http://www.esri.com/partners/alliances/ibm/index.html
5.
ftp://ftp.software.ibm.com/software/data/spatial/DB2SEss2.pdf
6.
ftp://ftp.software.ibm.com/software/data/spatial/db2sb.pdf
7.
ftp://ftp.software.ibm.com/software/data/pubs/brochures/spatial.pdf
8.
ftp://ftp.software.ibm.com/ps/products/db2/info/vr8/pdf/letter/db2ire80.pdf
9.
ftp://ftp.software.ibm.com/software/data/spatial/warehous.pdf
10.
ftp://ftp.software.ibm.com/software/data/spatial/esri.pdf
11.
http://www.esri.com/partners/alliances/ibm/pdfs/esri_ibm_flyer.pdf
12.
http://www.esri.com/news/arcnews/winter0405articles/ibm-spatially.pdf
13.
http://www.esri.com/partners/alliances/ibm/pdfs/db2_ibm.pdf
14.
http://www.esri.com/partners/alliances/ibm/pdfs/ads_ibm-esri.pdf
15.
http://www.esri.com/partners/alliances/ibm/pdfs/ads_arcuser_enhanced.pdf
16.
http://www.esri.com/library/whitepapers/pdfs/gis-technology.pdf
17.
http://www.esri.com/library/whitepapers/pdfs/idc_enterprise_apps_feb_2005.pdf
18.
ftp://ftp.software.ibm.com/software/data/spatial/esri2005/01.pdf
19.
http://www.opengeospatial.org/docs/99-049.pdf
Oracle Spatial
20.
http://www.oracle.com/technology/products/spatial/index.html
21.
http://www.oracle.com/technology/documentation/index.html
22.
http://www.gis.com/
PostGIS
23.
http://postgis.refractions.net
24.
http://www.freegis.org/database/viewobj?obj=659
25.
http://www.geospatial-online.com/geospatialsolutions/article/articleDetail.jsp?id=19932
26.
http://www.paragoncorporation.com/ITConsumerGuide.aspx?ArticleID=1
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