1 ICWS 2006, Chicago ICWS 2006 A Framework for Intelligent Web Services: Combined HTN and CSP Approach Incheon Paik, University of Aizu Daisuke Maruyama, University of Aizu Michael N. Huhns, University of South Carolina Presented by: Jingshan Huang Computer Science and Engineering Dept. University of South Carolina

2 ICWS 2006, Chicago Motivation  Solving real-life problems requires a set of appropriate services to be (1) composed via planning, (2) scheduled, and (3) executed. HTN (Hierarchical Task Network) : Planning CSP (Constraint Satisfaction Problem) : Scheduling  Problems of HTN-Only system ― Cannot satisfy scheduling efficiently ― Difficulty in finding an autonomous solution  Suggest a Novel WS Composition Engine: the HTN-CSP combined system

3 ICWS 2006, Chicago Hierarchical Task Network (HTN) Planning  To produce a sequence of actions by task decomposition from large tasks  Similar to classical AI planning  Can produce plans to reach a final goal, but it is not suitable for scheduling  We chose SHOP2 as our basic planner

4 ICWS 2006, Chicago Planning Domain Example (transport ?p) (at ?p ?x) (destination ?p ?y) (available-truck ?t) (dispatch ?t ?x)(!load ?t ?p)(!move ?t ?x ?y)(return ?t ?y) task: preconditions: subtasks: (dispatch ?t ?x) (!reserve ?t)(!move ?t home ?x) subtasks: (return ?t ?y) (!move ?t ?x home)(!free ?t) task: : Method : compound task subtasks: : primitive task : state

5 ICWS 2006, Chicago HTN-Only System Framework Input Domain Analyzer HTN Planner Web Service Executor planning problem Web Services Hotel Reservation WS Train Timetable WS Airplane Timetable WS … plan input data

6 ICWS 2006, Chicago HTN-Only System Framework Input Domain Analyzer HTN Planner Web Service Executor planning problem Web Services Hotel Reservation WS Train Timetable WS Airplane Timetable WS … plan input data I'd like to make a trip next week. I want to depart Aizu-wakamatsu at 14:00 and arrive at San-Francisco. Departure Location = Aizuwakamatsu Departure Time = 14:00 Departure Date = Feb. 21, 2006 Arrival Location = San-Francisco

7 ICWS 2006, Chicago HTN-Only System Framework Input Domain Analyzer HTN Planner Web Service Executor planning problem Web Services Hotel Reservation WS Train Timetable WS Airplane Timetable WS … plan input data (departure-location aizu-wakamatsu) (departure-time _1400) (departure-date _ ) (arrival-location san-francisco)) (trip) initial states: goal task:

8 ICWS 2006, Chicago HTN-Only System Framework Input Domain Analyzer HTN Planner Web Service Executor planning problem Web Services Hotel Reservation WS Train Timetable WS Airplane Timetable WS … plan input data (travel ?from ?to)... (travel-by-train ?from ?via) task: preconditions: subtasks: (travel-by-airplane ?via ?to) (available-train JR-Banetsu-West-Line aizu-wakamatsu _0600 koriyama _0712)...

9 ICWS 2006, Chicago HTN-Only System Framework Input Domain Analyzer HTN Planner Web Service Executor planning problem Web Services Hotel Reservation WS Train Timetable WS Airplane Timetable WS … plan input data (!travel-by-train JR-Banetsu-West-Line aizu-wakamatsu _1413 _ koriyama _1513 _ ) (!travel-by-train Tsubasa-186 koriyama _1525 _ tokyo _1648 _ ) (!travel-by-train Narita-Express-37 tokyo _1703 _ narita _1757 _ ) (!travel-by-airplane ANA-B2 narita _2000 _ san-francisco _1100 _ )

10 ICWS 2006, Chicago Problems with an HTN-Only System  Web service composition by a planner has limitations: Inefficient for autonomous finding solution in planning Not good for dealing user’s various requests Weak in maintenance Not efficient for scheduling

11 ICWS 2006, Chicago HTN-CSP Combined System Framework Input Domain Analyzer HTN Planner CSP Constructor CSP Solver Web Service Executor CSP representation planning problem CSP tuple Web Services Hotel Reservation WS Train Timetable WS Airplane Timetable WS … plan input data

12 ICWS 2006, Chicago Variable Representation Hotel Label Assigner Train Label Assigner Robot with Situation Calculus Control Master-Layer Sub-Layer Hotel Reservation Web Service ・・・・・・ CSP Solver Train Time ｔ able Web Service ・・・・・・ Airplane Time ｔ able Web Service CSP Constructor Z: variables D: domains C: constraints Knowledge Base Constraint-satisfied Label Worldwide Web Service UDDI Knowledge Base Constraint Check Assigner Management Assigner Repository Which assigner should be applied. HTN Planner Knowledge Base Information needed for HTN planning Domain Analyzer Information needed for constructing CSP tuple Domain Representation Constraint Representation Dynamic Request Trip Shopping ・・・・・・ Goal Sub-Goal Ontology Trip Domain Trip Domain Knowledge BaseOntology Request Data defined with Ontology Information needed for Domain Analysis

13 ICWS 2006, Chicago HTN-CSP Combined System Framework Input Domain Analyzer HTN Planner CSP Constructor CSP Solver Web Service Executor CSP representation planning problem CSP tuple Web Services Hotel Reservation WS Train Timetable WS Airplane Timetable WS … plan input data (riding-duration tokyo narita) = 0:54 (riding-duration koriyama tokyo) = 1:23 (riding-duration aizu-wakamatsu koriyama) = 1:00 (departure-time tokyo) = 17:03 (departure-time koriyama) = 15:25 (departure-time aizu-wakamatsu) = 14:13 (departure-date tokyo) = 2006/2/21 (departure-date koriyama) = 2006/2/21 (departure-date aizu-wakamatsu) = 2006/2/21 (arrival-time tokyo) = 16:48 (arrival-time narita) = 17:57 (arrival-time koriyama) = 15:13 (arrival-date tokyo) = 2006/2/21 (arrival-date narita) = 2006/2/21 (arrival-date koriyama) = 2006/2/21 (departure-time narita) = 20:00 (departure-date narita) = 2006/2/21 (arrival-time san-francisco) = 11:00 (arrival-date san-francisco) = 2006/2/21

14 ICWS 2006, Chicago Performance Comparison Solving Type Number of Web Service Invocation Processing Time (ms) Activity in Composition 1 HTN-Only = 4Total : 3039Planning HTN-CSP Combined = 4Total : 5789 Planning and Scheduling 2 HTN-Only4 + 2 = 6Total : 2661Planning HTN-CSP Combined = 6Total : 3187 Planning and Scheduling 3 HTN-Only0Total : 122Planning HTN-CSP Combined 0Total : 2248 Planning and Scheduling Scenario

15 ICWS 2006, Chicago Advantages of the HTN-CSP Combined System  Development Efficiency Scheduling is already integrated  Flexibility HTN-CSP combined system: ― Can represent complex problems more easily HTN-only system: ― Might produce scenarios that are hard to solve  Extensibility HTN-CSP combined system: ― Features can be added easily ― Many algorithms for solving CSPs available HTN-only system: ― To add new features, the planning domain must be rewritten in many cases

16 ICWS 2006, Chicago Conclusion and Future Work  Suggested a combined HTN-CSP architecture for automatic Web service composition Efficient for planning and scheduling  Future work Automating HTN – CSP encoding Fully automated problem solving (service composition) in a Semantic Web environment using this framework