1. 1 Developing Applications in Protégé: The Protégé Plugin Architecture Timothy Redmond Ontolog Forum 29-Jun-2006

2. 2 Overview What is a Plugin? How Plugins Work Plugin Types and Capabilities Plugin Packaging Plugin Bundling Plugin Licensing Other Development Models

3. 3 Out of Scope Standard Java Development Coding Packaging (jars) Utilities Implementation mechanisms Development environments Non-plugin Protégé extensions

4. 4 What is a Plugin? Extension to Protégé Requires no source code modifications Loaded and managed by system Changes way Protégé works Implementation of a Java interface Packaged as jars Installed in subdirectory of Protégé plugins

5. 5 How Plugins Work Protégé, at startup, loads jars directly below plugins subdirectory Jars contain manifest of contained plugins System creates instances of plugin System calls plugin methods when needed Dont call us, well call you.

6. 6 Plugin Source Extremely Simple Demo Plugins Available with the source for this talk

7. 7 Types of Plugins TabWidget SlotWidget KnowledgeBaseFactory (Backend) ProjectPlugin ExportPlugin CreateProjectPlugin

8. 8 Plugin: TabWidget What is it? Large piece of screen real-estate Can interact with domain KB browse, change, delete, corrupt What are its limitations? Difficult to supplement or even interact with other tabs How hard is it to create? Easy (1 day) Just implement the initialize() method

9. 9 Tab Plugin Configuration Protégé is built from plugins The Frame Counter Tab which we have added. Not enabled.

10. 10 Simple Tab Plugin

11. 11 Plugin: SlotWidget What is it? UI Control which allows the user to display and modify a slot value Follows a protocol for hiding interaction KB What are its limitations? Works best with a single slot How hard is it to create? Easy (1 day)

12. 12 Forms and the Slot Widget

13. 13 Forms and the Slot Widget

14. 14 Plugin: SlotWidget - Protocol Initialize() Describe how large a widget would like to be getValues() Protégé wants the value being displayed. setValues() Protégé wants to update the value displayed in the widget valueChanged() tells Protégé of an update isSuitable() setEditable()

15. 15 Plugin Type: KnowledgeBaseFactory What is it? Replacement for standard storage mechanisms Database External server … Allows for parsing of different file formats What are its limitations? Difficult to manipulate UI Implementations tend to be buggy How hard is it to create? Hard (>= 1 month) Consider Import/Export plugin instead

16. 16 Plugin Type: ProjectPlugin What is it? Code that executes when things happen to a project (create, load, display, close, etc) Get access to project, view, menu bar, tool bar and can modify them as you like How hard is it to create? Easy (1 day) Seven Possible Interfaces to implement

17. 17 Project Plugin Example

18. 18 Plugin Type: ExportPlugin What is it? Code that saves (part of) a knowledge-base in any format to somewhere else files, servers, web, … No change of the current backend No guarantee of lossless round trip No live connection How hard is it to create? Medium (1 week) Implement handleExportRequest()

19. 19 Export Plugin Example

20. 20 Plugin Type: CreateProjectPlugin What is it? Code that creates a knowledge-base from information from somewhere else files, servers, web, … No change of the current backend No guarantee of lossless round trip No live connection How hard is it to create? Medium (1 week)

21. 21 Plugin Type: CreateProjectPlugin canCreateProject() Describes when this import plugin can be used createCreateProjectWizardPage() The wizard for finding out where to get the data createNewProject() Creates the project from scratch buildNewProject() Builds the project from existing sources

22. 22 CreateProjectPlugin Example

23. 23 Types of Plugins TabWidget SlotWidget KnowledgeBaseFactory (Backend) ProjectPlugin ExportPlugin CreateProjectPlugin

24. 24 Plugin Packaging Plugin can contain doc and about box URLs or pages to integrate into the system Create a directory structure like: edu.stanford.smi.protegex.myproject/ myproject.jar otherlibrary.jar myproject_doc.html myproject_about.html plugin.properties Zip it up and give it to your friends

25. 25 Plugin Bundling Plugins of general usefulness can be bundled with the full release and made available to all users Advantage: You may get a lot of users quickly Disadvantage: You may get a lot of users quickly In order to be bundled the plugin must be: Well Formed Well Behaved Well Maintained

26. 26 Plugin Bundling – Well Formed jar file in an appropriate, recognizable directory approriate: edu.myorg.mygroup.myproject, not foo recognizable: last directory element: mytab not foo About Box and Documentation entries Minimal size minimal documentation links to more extensive documentation on web no PDF, MS Word, large image files no source at most one small example project readme.txt file if necessary isSuitable implemented if appropriate Is it requires certain sorts of projects or additional installation (shared libraries, etc)

27. 27 Plugin Bundling – Well Behaved Must work (not crash on startup) with the current release Minimal information (just errors) printed to the console window Single startup line is ok (but certainly not required) Use Java Logger for debugging Must start up and shut down smoothly No time consuming code executed in static initializer No long start up delays or modal dialogs that block the rest of the system Must free acquired resources in dispose()

28. 28 Plugin Bundling – Well Maintained Developer/maintainer responsive to problems. Does not mean that you offer 24x7x365 free support.

29. 29 Plugin Licensing Plugins are not affected by the Mozilla Public License (MPL) You can adopt whatever license you want for your plugin Open source (GPL, MPL, BSD) Proprietary You can (try to) sell your plugin See FAQ for more information on plugin and non-plugin licensing issues http://protege.stanford.edu/faq.html#08.00

30. 30 Plugin Summary Plugins provide flexible and powerful mechanisms for extending Protege in many ways. When you encounter places where the default UI is inadequate or clumsy for your needs (and you will!) think about developing a plugin. Think about contributing your plugin it back to the community.

31. 31 Standalone Application Description Write standalone Java Application Call into the Protégé API for knowledge base access Often evolves from a Tab Pros No need to install Protégé User doesnt need to know anything about Protégé Underlying model and data are as secure as you want Can use some or none of the Protégé UI, as desired Forms for classes and instances are available Some tabs will work Cons Iteration somewhat more difficult than as Tab

32. 32 OWL Model Interfaces Get Standard OWL Vocabulary E.g. owl:equivalentClass Create named classes & properties Java classes for all parts of the OWL Abstract Syntax Create OWL expressions (Restrictions) Listeners for Changes E.g. class creation, deletion, new properties

33. 33 Summary Plugin Development is often a good starting point Standalone applications easily built on Protégé Using only knowledge base Using also some/all of the Protégé UI