1. Grid Workflow Research update in SIG Dr. ZhenChun Huang Tsinghua Univ. NRSCC/RSGS/SIG Team Sep. 8th, 2004

2. Grid, Application Grid and SIG Grid –connects distributed resources by network –co-operates resources by standard protocols –creates virtual organizations dynamically and resolves application problems by the support of grid software. Application Grid –grid for a special application area –based on the general grid technology –provides many features to fit the application area additionally Spatial Information Grid –Application Grid in Spatial Information Application area –provides features for the Spatial Information Applications

3. Grid Architecture Grid Infrastructure Resources as ServicesApplications Tools Grid Middle ware Changes in infrastructure Application for the area special resources (services) Tools for the area The applica tion grid Workflow

4. Object of grid workflow Regard a grid application as a workflow based on resources in grid Provide a easy-to-use environment to develop, deploy and execute complex grid applications 3R –––– Object of workflow Choose the Right resource(person or machine) Do the Right thing At the Right time Grid WorkFlow Language, shortly GWFL Based on the open-source workflow engine osworkflow 2.6 Its language is a bit different from that designed by WfMC. Uses finite automaton model

5. Roadmap First half year of 2002 –No workflow support in our grid system –Develop application by Java/JSP directly Last half year of 2002—first half year of 2003 –Introduce BPEL to our grid system and develop demo applications based on it –(thank for He Chuan and Gu Lei, they led us to use workflow in grid) 2003 last half year — now –Give up BPEL and adopt GWFL based on OSWorkflow 2.6 instead –And develop some down-to-earth applications

6. Why GWFL instead BPEL GWFL Can Invoke Web Service only Invoke almost anything by “plug-in” No user/permissionProvides interfaces for user/permission Very difficult to interact with user in workflow Interact with user by “view” in workflow No source code and copyright reserved Open-source and can be modified freely (OSWorkflow)

7. Workflow Definition of GWFL A workflow Startup step Finish step (optionally) Step 2 Step … Step 1 A workflow has a “startup” step, a “finish” step (optionally) and several “internal” steps A step has several “status”, a step and its current status make up of a status of finite automaton

8. “Step” in GWFL Each step has several actions, and a action can perform a state-transition between steps. A Step Action Other Step

9. “Action” in GWFL An action includes: –1 view(usually Java Server Page) to show for the user –1 restricted condition to restrict availability of this action, and it can be a complex condition linked by AND, OR or NOT operator –0..n validators to validate the input data –0..n pre-function & post-function to perform before or after the action –0..n results to transit the status of finite automaton. One of the results should be “unconditional result”, and the others are “conditional results” with conditions –Or Split into several status, or join several status into one. –Results can have pre-function or post-function, too –All the components except view should be “plug-ins”, they may be: Java class, BeanShell, and BSF(support perlscript 、 vbscript 、 javascript)

10. An Action An action includes: An Action View Restricted Condition Validators Post-function Conditional Results & Un-Conditional Result Split Join Pre-function Condition Plug-in Validator Plug-in Function Plug-in Condition Plug-ins Function Plug-ins

11. A Sample workflow A sample workflow with 4 internal steps, a finish step, and a hidden startup step The hidden startup step Internal steps The finish step

12. Actions in a step A Step can have several actions (in the sample, it has 8 actions)

13. An Action An action with restrict-to conditions, pre-functions and 2 results. View of action

14. Restrict-to condition A complex restrict-to condition to restrict when the action is available Here, the restrict-to condition is: the status is “Underway” and the user is owner of this workflow The “condition” tag indicates a condition plug-in, it is a Java class here

15. Pre-functions and post-functions pre-functions or post-functions plug-in can perform some operation before or after the state-transition The function plug-in is Java class: org.caf.sig.workflow.function.Registry.Search And it needs 2 arguments named “serviceURL” and “type”

16. Results and state-transition This action has 2 results: a conditional result and a un - conditional result Result tag indicates a conditional result, its condition is a simple condition which plug-in is written in Java An unconditional-result tag can be regarded as a “default” result The next step State-transition

17. Develop function plug-in by Java A function plug-in class in java should implement the interface org.thgrid.gwfl.workflow.FunctionProvider and do any thing you want to do in function execute() The following is a example public class NewFunction implements FunctionProvider { public void execute(Map transientVars, Map args, PropertySet ps) throws WorkflowException { WorkflowContext context = (WorkflowContext) transientVars.get("context"); String argName = ParamUtil.getValue(transientVars, args, "name"); ps.setString("error", "ok"); } }

18. Develop condition plug-in by Java A condition plug-in class in java should implement the interface org.thgrid.gwfl.workflow.Condition and return whether condition is true in function execute() The following is a example public class CustomSelect implements Condition { public boolean passesCondition(Map transientVars, Map args, PropertySet ps) throws WorkflowException { WorkflowContext context = (WorkflowContext) transientVars.get("context"); String argError = ParamUtil.getValue(transientVars, args, “error"); return “ok".equalsIgnoreCase(argError ); } }

19. View of action A view of action is a special JSP fragment "> "> These codes must be included for the execution of workflow By gwfl custom tags, properties in PropertySet can be accessed

20. Update in SIG Workflow in SIG is the same as it in general grid essentially Because the SIG workflow is used for EO information application, there should be some additional features and functions in SIG workflow. And these should be our work –Develop plug-in library for Spatial Information applications in SIG –Make up a “workflow library” framework so that typical workflows can be stored for SIG –More powerful toolkits for developing, deploying and executing workflows in SIG –And so on

21. Plug-in library Plug-ins for the functions(pre- & post-), conditions and validators often be used, –Typical functions such as RS image processing, GIS data processing, RS & GIS data discovery, etc. –Typical conditions such as RS meta-data conditions, RS data & GIS data feature conditions, etc. –Typical validators such as RS meta-data & image validators, GIS data validators (for format, area, precision, etc)

22. Workflow library & toolkits Workflow library framework –Workflow design & test –Workflow register & discovery –User management & authorization –Co-operate with other parts of SIG, such as user interface, resource registry, etc. Some typical workflow to put in the library Workflow toolkits should include –Workflow editor with a friendly UI (beta version available ) –Workflow debugger to debug the workflow (on the road) –And so on

23. Applications Used in the 863 project: “Application Grid on Forest Resources and Forestry Ecology” (or often shortly, National Digital Forestry Grid, DFG) –We develop almost all the applications in this project by GWFL –The example we showed is one of these applications, too And it will be open-source (under GPL or LGPL), too –We are arranging source codes for release

24. Thank you