AGGREGATE PATH INDEX FOR INCREMENTL WEB VIEW MAINTENANCE Author: Li Chen and Elke Rundensteiner Department of Computer Science Worcester Polytechnic Institure Presented by Pengpeng Lu

OUTLINE OBJECTIVE INTRODUCTION MAINTENANCE STRATEGY MAINTENANCE APPROACH EVALUATION CONCLUSION

OBJECTIVE DEVELOP EFFICIENT WEB VIEW MAINTENANCE TECHNIQUE Web Web1Web2 Web3 Web4Web5 Web7Web6

INTRODUCTION WEB DATA: DYNAMIC NO “STRICT SCHEMA” FOR XML FILE WEB DATA NOT EASY TO BE SEPARATED WEB VIEW MAINTENANCE APPROACHES RE-COMPUTE FROM SCRATCH---NOT EFFICIENT INCREMENTAL MAINTENANCE---EFFIEIENT AGGREGATE PATH INDEX (APIX)

MAINTENANCE STRATEGY DOM TREE STRUCTURE (XML DOCUMENT)

MAINTENANCE STRATEGY WEB VIEW SPECIFICATION (XQL) Define web view favorite_entries as and price <$20 and item=“book”] and price <$20 and item=“book”] E S emq p i QUERY TREE APIX INDEX: I (v) v1v1 v2v2 v3v3 V 4…

MAINTENANCE APPROACH TWO-STEP: PATH PATTERN EVALUATION Store “qualified” objects into APIX PREDICATE VALUE EVALUATION PATH PATTERN EVALUATION and price <$20 and item=“book”]

MAINTENANCE APPROACH PREDICATE VALUE EVALUATION Evaluation Vaue (ER): True/1 False/0 View Object: 1.Path Pattern Satisfiable 2.ER Value is True Data Update Operations: Insertion Deletion Change

MAINTENANCE APPROACH CHECK IRRELEVANT CASES: Query Irrelevant Update Value Irrelevant Change Irrelevant Deletion Example: RELEVANT CASES: Example:

COST ANALYSIS Cost naive =C E +C s +C c +C e + C m +C q +C p +C i Cost APIX =1+(C’ m +C’ q +C’ p +C’ i ) /2 4 -1

ADVANTAGE DISADVANTAGE Prune the traversal space---reduce the accesses to base data Cache a reduced set of relevant objects---save index space APIX index table cost extra space for the columns

CONCLUSION APIX STRUCTURE WAS PROPOSED FOR INCREMENTAL WEB VIEW MAINTENANCE THROUGH COST ANALYSIS, APIX FOR WEB VIEW MAINTENANCE DEMONSTRATED ENHANCED EFFICIENCY