OO GIS at Ispra Project Vision: To establish at Ispra a permanent centre of expertise in object-oriented GIS technologies based around an in-house developed and maintained OO-GIS research application based on a commercial OO-GIS product.

• Deployment architecture: which software runs on which machine, how many large software packages are active, what software is commercial, what configured and what new software is to be written.
• Software Component Architecture: which packages are written in which languages, how many software processes are running, what the interfaces are between packages (DLL, Corba etc.)

Commercial OO GIS Requirement

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1. Gothic as Repository only

Smits' C++ raster toolkit software used for:

• Raster segmentation algorithms.
• Raster generalisation algorithms.
• Class structure of 40 Class III CORINE landcover classifications.
• Different recognition, classification and update methods for each landcover type.

• Import data from CORINE (ESRI shapefiles) into single Gothic store (Gothic Translate®)
• Maintain all landcover data as topologically-connected polygons on all "imports" (from CORINE using Translate)
• Provide  version-management  of rasters to support on-going C++ processing by several users (Gothic Data Server).
• Provide conversion of raster to version-controlled topologically connected polygons on final "saves" from the C++ code.
• Provide version-management of vector (polygon) datasets from single store to all users (Gothic Manage®)
• Provide C interface through PLUS option which is used (in this architecture option) only to offer a set of functions similar to OGC Simple Grids: load and save.
• All data loaded into C++ from Gothic is rasters
• Export data to CORINE (any standard format, e.g. VPF, DXF ESRI shapefiles) from single Gothic store (Gothic Translate®)

Advantages

• No need to duplicate class hierarchies in both Gothic and C++ toolkit.
• Less of Gothic system needs to be learned: easier introduction.
• Full speed of C++ available as soon as it is debugged and runs.
• Expert programmer familiar with the C++ toolkit is available immediately on site.
• Careful choice of PLUS functions would make porting of system to non-Gothic OGC-conformant spatial repositories possible in future.
• Can use exception handling in C++ which is not available in LULL.

Disadvantages

• Possible future porting of system to non-Gothic OGC-conformant spatial repositories would drop the topological constraint and version management capabilities.
• No update of vector data using raster images, i.e. this option drops the most innovative part of the project.
• No mixed raster/vector working. This is not an explicit goal of this project's Vision Statement but it is a very significant advantage that all published papers describing this type of work have listed as the most important capability. If it is not important for the specific requirement here  it is likely that this demonstration project is too narrowly focussed or that we are attempting something we don't understand.
• Have to re-write (duplicate) the sophisticated buffered land classification functions supplied with IGIS.
• Writing logic in C++ (compile, link, run) is slower to debug than in LULL (interpreted inside Gothic)
• Have to write new user interface to support necessary functions
• Programming resource offered by Laser-Scan has low productivity because of unfamiliarity with Smits' PhD project software.

Risks

• Schedule delay because Philip Sargent and Laser-Scan staff find it impossible to contribute to C++ programming because of lack of documentation and training materials for this PhD project software.

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2. Gothic IGIS used for all functions

Gothic system is used for all functions listed in high-level use case.

• Import data from CORINE (ESRI shapefiles) into single Gothic store (Gothic Translate®)
• Maintain all landcover data as topologically-connected polygons all the time (Gothic Data Server)
• Provide version-management of vector (polygon) datasets from single store to all users (Gothic Manage®)
• Export data to CORINE (any standard format, e.g. VPF, DXF ESRI shapefiles) from single Gothic store (Gothic Translate®)
• Class structure of 40 Class III CORINE landcover classifications.
• Different recognition, classification and update methods for each landcover type.

IGIS is a Gothic Developer extension. The Integrator variant (for Win32 clients) shown in the diagram does not provide access to all the extra facilities in IGIS which are not in Developer and is therefore not a possibility for this project's schedule. Note: All diagrams copyright © Laser-Scan Ltd. 1998.

Future Gothic variants in development will permit the following architectures:

Advantages

• No need to install, configure and learn the PLUS interface option for IGIS until prototype complete.
• Better focus of work within a single development environment
• Full integration of "reflex methods" ("events") for object-oriented code handling constraint violations: ensures better data integrity
• Full raster/vector working appropriate for updating vector polygon shape using raster data
• Simultaneous access to previous polygon classification and current polygon classification
• Full object-oriented GIS capability available for all functions, no constraint to operate across the PLUS interface
• No need to duplicate class hierarchies in both Gothic and C++ toolkit
• Full use of sophisticated buffered land classification functions in IGIS
• Full use of existing sophisticated user-interface supplied with IGIS
• Fits perfectly with expertise of programming resource offered by Laser-Scan
• Writing logic in LULL (interpreted inside Gothic) is faster than in C++ (compile, link, run).
• Directly useable in future Laser-Scan deployment architectures.

Disadvantages

• Paul Smits' has to learn Gothic before he can become productive on the project, or he is not used as a programming resource until prototype finished.
• System is inherently in Gothic and cannot be ported to another GIS (true for extensive use of any OO GIS)
• Much of Gothic system needs to be learned.
• Full speed of C++ available only after prototyping finishes and optimisation phase begins.
• No exception handling in LULL, have to use explicity return codes.

Risks

• Schedule delay because some essential functions which may  not be available in the existing IGIS fast library may be very complex to write in LULL:   a language not designed for pixel manipulation.

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2. Gothic IGIS and Smits' C++ Used Equally

Gothic system is used for:

• Import data from CORINE (ESRI shapefiles) into single Gothic store (Gothic Translate®)

Advantages

• Some raster/vector working appropriate for updating vector polygon shape using raster data

Disadvantages

• Complex and large.

Risks

• Schedule delay, nothing will work until it all works.