Christophe Durand, Brigitte Guillaumont, Jean Prou

Patelle: Graphic Programming of GIS Processing Chains from ArcView

Patelle uses ArcView as a graphic editor to describe, tune and activate GIS processing chains needed by management and planning GIS projects. Each step of a chain is visualized in a view where parameters appear as graphic objects. Patelle offers a set of pre-defined process templates which can be combined into a chain. These include frequently used operations based on ArcView, ArcInfo, ERDAS Imagine, DOS or UNIX commands as well as custom templates added by advanced users.

The graphical metaphor hides the complexity of the commands involved as well as the location of the machine on which processing is performed. It provides ArcView users with a uniform and simple access to tested and on-line documented processing capabilities.

Two marine environment projects have demonstrated Patelle's capacity to enlarge the community of GIS users in our oceanographic research centre.

INTRODUCTION

The results of GIS projects are often produced by combining georeferenced data coverages. The tuning and activation of a GIS processing chain generally require use of complex software tools (vector processing, image processing, UNIX or DOS commands, etc.)

PATELLE (Prototype pour l'Aménagement du Territoire en Environnement Littoral), developed under ArcView, offers to GIS users a simple access to the functions needed to produce a GIS project result.

This paper introduces Patelle's objectives and main functionality. It also briefly describes how Patelle can be used and how it was designed and implemented.

It was written for thematicians who might use Patelle to create, tune and activate GIS processing chains and for managers and planners who may use it as a tool for their decision process. Knowledge of ArcView, although not mandatory, is recommended in order to take advantage of the information contained in this paper.

CONTEXT

Patelle originated from the need of the Sillage group and its partners within IFREMER.

IFREMER (Institut Français de Recherche pour l'Exploitation de la MER - The French Institute of Research and Exploitation of the Sea) is a French government research agency, established in 1984. It is a public establishment, partly funded by the state carrying out academic, industrial and commercial activities involving 1200 engineers, researchers, technicians and administrators worldwide in about 30 different locations. The IFREMER annual budget is almost 1 billion FF.

The Sillage group (Systèmes d'Informations LocaLisées pour l'Aménagement et la Gestion des Espaces côtiers et marins), was created in 94 at IFREMER Brest. Sillage's main objective is to demonstrate the interest of geographical information systems (GIS), remote sensing, and image processing for the management and the control of the coastal zone.

The development of a GIS project often involves the cooperation of various thematic specialists in order to identify relevant data, acquire and validate this data, select combination modes and propose an efficient display of the results.

PATELLE OBJECTIVES

PATELLE is designed for IFREMER thematicians specialising in coastal zone environment, resources and land use, and for managers of these areas. It offers a unique platform which handles all the phases of a study:

create a GIS processing chain and set its parameters,
pilot the execution of the chain steps,
display the results and produce reports and maps.

Figure 1 : Example of Patelle elementary process

Provide graphic programming of GIS processes

The main originality of Patelle is to use graphic programming of the processing chain. Each elementary step of a processing chain is visualised in a diagram (c.f. figure 1).

The process parameters are visualised as graphic objects. Each graphic object has a set of properties attached to it : pathname and type (for files), string (for text parameters), name of program, code, name of the machine (for commands).

This mode of representation allows operations coded in AML language (ArcInfo, Grid), Avenue (ArcView, Spatial Analyst), SML (ERDAS Imagine), DOS, Shell, Perl, etc. to be used from the same user interface.

The graphical metaphor hides the complexity of the process implementation : each process is a "black box" which can be combined with others into a chain.

Promote the diffusion of process templates

Patelle is delivered with a library of pre-defined process templates which include the most common operations : data import, cover merge, raster/vector transformation, combining images, etc.. This library offers a set of "black box" routines which do the job, but do not require specific programming skills from the user or any knowledge of how the job is actually implemented.

Each template has an associated on-line help which describes in detail the parameters of the process and when necessary syntax information or recommendations written by the author of the template.

This function of Patelle allows distribution of tested and validated processes and facilitates reuse of the code. It also stimulates the spread of GIS techniques out of the circle of GIS programming experts.

New templates can be added to this library and the on-line help is generated and updated automatically.

Portability

Patelle is available on PCs and UNIX workstations (Sun and DEC Alpha). Processing chains created with Patelle can be used in both environments.

Take advantage of network resources

Patelle can activate local or network processes. The access to servers such as ArcInfo is provided through ArcView inter-applications communications protocols (DDE and RPC).

This function allows to share more efficiently software tokens available on a network and to take advantage of available CPU resources.

Offer different levels of use

Programmer: to add new process templates,
Thematician: to create, tune and activate a processing chain and display results,
Managers and planners: to use an existing processing chain, tune its parameters, activate it and display results,
Demonstration: to display the details of the chain and its results.

Patelle and ArcView

Patelle is strongly linked to ArcView concepts and data model.

It is essential to be an experienced user of ArcView in order to use Patelle. ArcView was selected in early 1995 by the Sillage group and since then has spread considerably within IFREMER. Patelle helps take advantage of this situation and greatly enlarges ArcView possibilities.

Import and export procedures have been carefully studied in order to be opened to other data formats used by Sillage partners.

FUNCTIONAL DESCRIPTION

The management of a GIS processing chain involves the following phases :

Create the processing chain: allows graphical declaration of the structure of the steps and selection of the type of each elementary process,
Set the chain parameters: associate a value to each parameter involved in the chain : file names, numerical values, etc. The chain check ensures that the chain structure and the parameters values are coherent,
Pilot the chain execution: allows the execution of all or part of the processing chain to be started,
Visualize results: displays results in views, tables, graphs and allows preparation of reports and layouts.

An advanced function of Patelle allows configuration of its external interfaces and addition of new process templates.

User Interface

Patelle is available in French and English versions.

Figure 2. User interface description

The user interface includes :

The Menu bar: to activate actions from a menu,
the Button bar: gives a faster access to specific functions,
the Tool bar: associates an action to a click in a document,
ArcView functions: to display data in views, tables, graphs, layouts,
Patelle diagrams: graphical description of processing chains. A diagram is a special ArcView document with a specific graphical user interface (DocGUI) A diagram contains graphic objects which represent either chain steps or the parameters of an individual process.

Create a processing chain

In Patelle, a processing chain is described with a hierarchy of steps. Each step is either made of sub-steps or is an elementary process.

Figure 3. Example of root diagram (left) with sub-steps (center) and a process (right)

The creation of a processing chain involves the following phases :

Create the root diagram,
Create the sub-steps in the root diagram,
Create the elementary processes by selecting them from a library of available process templates. Each process is made of input and output parameters, the command associated and the name of the machine on which the command is executed.

Patelle also provides the following functions :

Navigate in the processing chain,
Improve the graphic look of the chain by adding to the diagram graphic objects which enrich or document steps and processes (drawings, zoom in and out, new graphic attributes, etc.),
Copy/Paste/Delete the processing chain components. When a step is copied or deleted, the graphic object, its diagram and all the sub steps are implied in this action.

Set a processing chain parameters

This function allows the setting of the values of the parameters used when the process command is executed :

set the value of a text or numeric parameter,
set the name of a file,
change a file properties,
select the pathname of a file,
check the processing chain : this function scans the chain and checks that the files used by each process have been imported or produced earlier by the chain, and that their types are consistent. It also checks that all the parameters values have been set.

Figure 4. Update of a file properties

Pilot the execution of a processing chain

This function allows execution of a processing chain or part of it and display of the execution results.

Run all the processing chain,
Run a diagram: activates the execution of the steps or the process displayed in the current diagram. The number associated to each step determines the order in which they will be activated.
Run a step: activates the execution of the sub-steps of the selected step(s).
Run a process: activates the execution of the current process if its parameters have been modified or if input files are newer than output files. If the process calls a service which is not available, or if it returns an error, this process and all its other steps are marked in error and the chain is stopped.
Stop the processing chain : allows interruption of the chain execution at the end of the current running process.

Figure 5. The logbook windows after the activation of an ArcInfo process

Display results

This function allows display of the results in tables, graphs and view and preparation and printing of reports and layouts.

It is directly inherited from ArcView and is fully described in ArcView user manuals and on-line help.

Add process templates

Patelle is delivered with a set of process templates. If necessary, the user can also add his own templates.

A template is made of two parts : a graphic description in a diagram of all the objects of the process (parameters and commands) and a code section which contains the commands sent to the local or network service which executes the process.

Figure 6. Example of graphic objects

Patelle configuration includes three sub-functions :

Draw the process graphic objects: creates the diagram which will be cloned when the user creates a process,
Create the command code: used to write and test the code associated to the process commands. The following languages are supported : Avenue (ArcView, Spatial Analyst), AML (ArcInfo), Shell (UNIX), Perl (UNIX).
Export the template into the template library : during the export, an on-line help is automatically generated by extracting the comments associated to the process and its objects.

PATELLE PROGRAMMING

Design

Patelle analysis and specifications were carried out under TeamWork using the SA/RT module.

The object oriented design was made on the basis of the OMD method from J. Rumbaugh.

Figure 7. Patelle design : object classes architecture

Patelle was written entirely in Avenue language except for RPC communication programs needed on UNIX workstations only.

Since Avenue does not allow to create your own class of objects, a set of scripts was developed to implement this functionality.

Each script includes a header which enables automatic production of the design documentation in hypertext HTML or ArcView on-line help format.

Implementation

Patelle has been implemented as an ArcView 3 extension which can be added or removed from a project.

CONCLUSION

Patelle is currently being tested to answer questions asked by GIS projects for fisheries management in the Mediterranean and aquaculture near La Rochelle.

The concept of graphic programming has demonstrated its capability for the handling of a complex processing chain to all the partners of the GIS project.

REFERENCES

[Durand-95] Dossier de Spécifications Fonctionnelles de PATELLE, Groupe Sillage, 95, Réf: DITI/DSI/MU/CD-020.

[Durand-95] Manuel utilisateur de PATELLE, Groupe Sillage, 95, Réf: DITI/DSI/MU/CD-021.

[Esri-95] Introduction à Arc/View, Esri, UBS 1.5M5/95.

Christophe Durand, ( Christophe.Durand@ifremer.fr)
Brigitte Guillaumont, ( Brigitte.Guillaumont@ifremer.fr)
IFREMER, Institut Francais de recherche pour l'exploitation de la Mer
Groupe Sillage
BP 70
29280 PLOUZANE, France
Tel : (33) 98 22 43 18
Fax : (33) 98 22 45 33
WWW : DITI/DSI service développement de systèmes informatiques

Jean Prou, ( Jean.Prou@ifremer.fr)
CREMA, Centre de recherche en écologie marine et aquaculture
BP 5
17137 L'HOUMEAU, France
Tel : (33) 46 50 06 10
Fax : (33) 46 50 06 00