Rule-Based Programming for VORBs Bertram Ludaescher Arcot Rajasekar Data and Knowledge Systems San Diego Supercomputer Center U.C. San Diego

2 ROADNet/VORB Design 12/01 Background and Overview Goals... –streaming real-time environmental data... –... over wireless networks, –... seamlessly collecting, integrating, and archiving –... heterogeneous multi-disciplinary data!.... and The Noble Path –extending the ORB to an all-powerful VORB! => dynamic reconfiguration and programming of ORBs via a layer of rule-programmable VORBs –build VORBs as SRB-lets (= extensions to SRB)

3 ROADNet/VORB Design 12/01 All about VORBs... Virtual Object Ring Buffers –overcome the static bindings... Applications  ORB  RealTimeSensors –... by rule-based “VORB mediators” –... VORBs need metadata about available ORBs, the connected sensors, and “fellow VORBs” => VORB catalog/registry

4 ROADNet/VORB Design 12/01 Possible VORB Components actual data transfer VORB Archive VORB Archive Event-Condition- Action Rules Event-Condition- Action Rules VORB Cat VORB Cat VORB Rule Engine VORB Rule Engine SrcORB Client/App. virtual data transfer (ctrl msgs)

5 ROADNet/VORB Design 12/01 VORB Active Rule Engine VORB Cat VORB Cat SrcORB Client/App. VORB Rule Engine Event-Condition- Action Rules Event-Condition- Action Rules SrcORB SRC Events USR Events Condition Evaluation VORB Archive VORB Archive SrcORB Client/App. ORB

6 ROADNet/VORB Design 12/01 Event-Condition-Action (ECA) Rules Rule Syntax –ON IF THEN Rule Semantics –whenever the event occurs, the rule is triggered, the condition checked and – if satisfied – the action is executed  Active Database Rules (=ECA rules)  Flexible, Dynamic Programming Style Declarative Reconfiguration based on... –logic language for conditions, –logic language for complex events detection, and –... an algebraic action language

7 ROADNet/VORB Design 12/01 Events Database Events –INS, DEL, UPD, BOT, EOT, ABORT, COMMIT, ROLLBACK, CHECKPOINT Temporal Events –absolute –relative, periodic,... Application-Specific/Data Source Events –sensor-value > threshold –ORB up/down –...

8 ROADNet/VORB Design 12/01 Event Algebra for Complex Events

9 ROADNet/VORB Design 12/01 Event Consumption for Composite Events

10 ROADNet/VORB Design 12/01 Conditions... may be even more “heavy-weight” than events... involve the registry/VORB Cat/VORB DB... may be quite similar to complex event detection => temporal query conditions  complex events

11 ROADNet/VORB Design 12/01 Temporal Queries Homework –replace such employee/salary temporal queries by ones that correspond to interesting real-time sensor ones (from the sources)... reconfiguration ones (from the client/apps.)

12 ROADNet/VORB Design 12/01 Compiling Temporal Queries into Rules Complex event detection and evaluation of temporal queries can be implemented by a translation to “state-aware” logic rules.

13 ROADNet/VORB Design 12/01 Actions Reconfiguration Actions: –brokering actual data paths –adapting sampling rates, transmission rates,... –turning on/off data archival, automatic dissemination,... Will query and update the VORB/Cat

14 ROADNet/VORB Design 12/01 Summary and Outlook Active (Event-Condition-Action) Rules provide flexible rule-based programming for dynamic reconfiguration of VORBs ECA rules will be executed in a SRB environment (SRB-lets) SRB/MCAT can also manage the VORB/Cat Tasks –VORB use cases! –VORB requirements and specification –design of event, condition, and action sublanguages –design of rule evaluation algorithm –implementation

Specific VORB Aims

16 ROADNet/VORB Design 12/01 Design Aims –Virtualized Access to Real Time Data Streams VORB –Virtualized Integration of Real Time Data Multiple VORBs –Private Virtual Real Time Data Management Private VORBs –Rapidly Configurable RT Data Networks Demand-driven Reconfigurable VORB Requirements –Federated Resource Brokering –Metadata Catalog –Rule-driven Data Aquisition and Integration –Extensible ORBs

17 ROADNet/VORB Design 12/01 VORB- A Real Time DataGrid Architecture Aim #1: –Virtualized Access to Real Time Data Streams Hide Physical Aspects of RTD Resources –Handling Heterogeneity of Resources –Plug and Play Uniform Protocol & API Common Authentication & Authorization Replication, Fault Tolerance, Load Distribution Caching, Scheduling, Data Placement Uniform Name Space – Persistence & Discovery

18 ROADNet/VORB Design 12/01 Federated VORB Aim #2: –Virtualized Integration of Real Time Data Integrate packets from multiple data streams –Heterogeneous & Distributed RT Data Resources Hide Logical Aspects of VORB-accessed Resources –Virtualized Schema –Rule-based Integration Uniform Protocols & API Metadata-based Discovery

19 ROADNet/VORB Design 12/01 MyVORB Architecture Aim #3: –Private Virtual Real Time Data Management Configurable Integration Information Discovery Programmable Methods and Active Rules

20 ROADNet/VORB Design 12/01 Demand VORB Aim #4: –Rapidly Configurable RT Data Networks Based on situation and demands More sensors activated/brought online Changing VORB Federation Rapid Information Publication Fault tolerance

21 ROADNet/VORB Design 12/01 Resource Broker SRB extension to ORB & other RT resources –Resource Transparency Local or Remote, Resource Type & Access Method –Location Transparency Stream Names, Stream Structure/Schema –Cross-Domain Authentication –Replicated Data Management –Data Redirection, Load Balancing, Fault Tolerance –Data Discovery –Uniform API, Protocol

22 ROADNet/VORB Design 12/01 Metadata Catalog System-level Metadata –Sensor info, Data Format Info –Resource Info, Method Info, Event/Trigger Info –User Transparency Uniform User Name Space Access Control –Uniform Data Stream Name Space – Persistence Logical Metadata - Conceptual Info –Data Discovery –Data Integration Info User-defined Metadata

23 ROADNet/VORB Design 12/01 Rule-Driven Integration and Extensible ORBs Use of Virtual XML Data Views –metadata (and data?) sources as queryable XML databases  develop XML Schema for source metadata  XML queries (e.g., XPath, XQuery tools) Active Rules for Dynamic Reconfiguration –Event-Condition-Action rules as SRB extensions –develop VORB protocols and corresponding XML DTD –trigger execution based on “action tags”!? Rule Engine within VORB-SRB –implemented in... (Prolog, Python, Perl???) Extensible ORBs –...