HUX: Handling Updates in XML DataBase Systems Research Group Departmet of Computer Science Worcester Polytechnic Institute, Worcester, MA 01609, USA Ling Wang, Elke A. Rundensteiner, Murali Mani and Ming Jiang

Updating XML Views for Data Integration XMLRDB XMLOODBXML Time Magazine Protein Sequence Database (PSD) Citi Bank American Airline Amazon Google Map Virtual XML Views News Biologist Google map Online billing e-ticketShopping ? ?

Examples queriesviewsobservationreason …. …. view elements of region are never updatable base tuples used will also contribute to a view element of Regionnew …... …. view elements of nation are always updatable each used base tuple will join with one view element of Region only R_Key … View Region * Regionnew * View Region Nation * *R.regionkey=N.regionkey N_key … RegionNation

Challenges Update Translatability Checking  Does at least one correct translation exist?  If yes, what are the candidate translations?  If not, where the view side effect could happen? Update Translation Strategy  What are the correct translations?  How to find the correct translations?  Which one is the best translation?

Criteria of correct translations View side-effect free No “ extra ” updates Option 1: Face with unexpected side effects Option 2: Expensive Rollback to fix problems (3) U U(D) V D View Query (1) (2) u u(V) View Query (4) Accept Update if there exists a correct translation Otherwise

Naive Approach -- Pure Data-driven Check Pure data-driven check  Guarantee “ safe ”  Guarantee “ complete ” But:  Very inefficient for XML view updating Data examination for all view nodes Core Idea: When updating a view element, base tuples that contribute to other view elements should remain untouched.

ValidInvalid UntranslatableTranslatable View Update Uncertain Untranslatable Translatable Schema Data HUX I: Exploiting Schema Knowledge Schema-driven translatable For every update on any element of the schema node: There is at least one correct translation Schema-driven untranslatable For every update on any element of the schema node: There does not exist any correct translation

View Elements Classification  Classify schema nodes into Self, Ancestor, Descendent, Others  No side effects on any element of SADO schema nodeAD O O S View side-effects Classification When updating a relation r to update a view element ve i: (1) r may contribute to the existence of vej, ve j = ve j (2) j may get deleted. j is a relation that refers to r and contribute to vej, vej = vei

Exploiting Schema Knowledge (Con’d) Core Idea: When updating a view element, relations that contribute to other view elements should remain untouched. Pros: Efficiency: use schema knowledge only Cons: Conservative: always assume the worst case View Region Nation Customer Orders * * LineItem * * * R.regionkey=N.regionkey N.nationkey=C.nationkey C.customerkey=N.customerkey O.orderkey=LI.orderkey Regionnew * LineItem ? Nation ? Regionnew ? Can we delete a view element whose schema node is..

HUX II: Schema-directed Data-driven Check data-driven translatable For the given update on an element of the schema node: There is at least one correct translation data-driven untranslatable For the given update on an element of the schema node: There does not exist any correct translation ValidInvalid UntranslatableTranslatable View Update Uncertain Untranslatable Translatable Schema Data

Schema-directed Data-driven Check (Con ’ d) Core Idea: When updating a view element, base tuples that contribute to other view elements should remain untouched. Not Pure Data-driven Check! Only check the part where schema check cannot perform View Region Nation Customer Orders * * LineItem * * * R.regionkey=N.regionkey N.nationkey=C.nationkey C.customerkey=N.customerkey O.orderkey=LI.orderkey Regionnew * Can we delete a view element whose schema node is Regionnew ?

HUX: Handling Updates in XML View Query STAR: Schema-driven Translatability Reasoning SDC: Schema-directed Data Checking SQL Update Generator HUX Data Storage Oracle Valid User Update Query Uncertain SQL Updates Annotated Schema Graph Generator XML/RDB Schema ASG Fail Untranslatable Error Message DB2SQL-ServerSybase Success Translatable

Experiments: HUX vs. Data-based TPCH Benchmark Data-based XML view updating (DXVU) Extend the relational view update system [CWW2000] to perform XML view check Observation (1) Schema cases: HUX performance much better than DXVU. Great performance gain! (2) Data cases: Two systems are comparable. View Region Nation Customer Orders * * LineItem * * * R.regionkey=N.regionkey N.nationkey=C.nationkey C.customerkey=N.customerkey O.orderkey=LI.orderkey Regionnew * Schema translatable Schema untranslatableData check

Contribution Proposed theoretical foundation for XML view updates. Proposed schema-centric view updating algorithm. Proved the correctness and completeness. Implemented as an extension of Rainbow query engine. Demonstrated efficiency through experiments.

Rainbow Project Recent Publications L. Wang, E. A. Rundensteiner, Murali Mani and Ming Jiang. HUX: A Schemacentric Approach for Updating XML Views. In CIKM, 2006 to appear L. Wang, E. A. Rundensteiner and Murali Mani. UFilter: A Lightweight XML View Update Checker. In ICDE, 2006 L. Wang, E. A. Rundensteiner, and M. Mani. Updating XML Views Published Over Relational Databases: Towards the Existence of a Correct Update Mapping. In DKE Journal, L. Wang, S. Wang, B. Murphy, and E. A. Rundensteiner. Order Sensitive XQuery Processing over Relational Sources: An Algebraic Approach. In IDEAS, L. Wang and E. A. Rundensteiner. On the Updatability of XQuery Views Publised over Relational Data. In ER, pages 795–809, 2004.

Problem Space

HUX vs. Relational View Update System View Region Nation Customer Orders * * LineItem * * * R.regionkey=N.regionkey N.nationkey=C.nationkey C.customerkey=N.customerkey O.orderkey=LI.orderkey L LO LOC LOCN LOCNR Data-driven relational view update (RVU) system [CWW2000] Best case --- find translation at first probe. Worst case --- find it at the last probe. HUX: Only schema-driven check Observation: HUX is better than RVU even for the best case.

Experiments  HUX vs. Non-guaranteed (unsafe) system  HUX vs. relational view update system  HUX vs. pure data-driven XML view update system  Performance of HUX  Usefulness of HUX (user study) Experimental set up  TPCH benchmark  Stop criteria: First Correct Translation (FCT) Exhaustive search criteria: Find All Correct Translations (ACT)  Parameters: Database size Key and foreign keys Element to be deleted in the view View size