September 2000XML Workshop, IIT Bombay Indexing of XML Data Raghuraman Rangarajan KReSIT, IIT Bombay.

September 2000XML Workshop, IIT Bombay Plan of Talk Why is indexing needed? Queries and Indexes in Traditional DBMS Querying in XML Indexes: Path, Value Conclusion

September 2000XML Workshop, IIT Bombay Why is Indexing Needed? Allows fast access to data by replicating portions of the data in special purpose structures. Despite the additional cost (storage, maintenance and complexity) they have shown to be useful in evaluating queries.

September 2000XML Workshop, IIT Bombay Queries and Indexes in Traditional DBMS DatabasesQueryExample RelationalAssociative SELECT name FROM account WHERE acctNo =14 OOPath Expressions SELECT X.name FROM dept.empl X

September 2000XML Workshop, IIT Bombay supplier An XML Fragment name address part subpart name address part supplier ( with leaf values omitted) subpart supplier

September 2000XML Workshop, IIT Bombay Queries in XML 1.SELECT X FROM part._*.supplier.name X 2. Select X From part._*.supplier: {name X, address: “Mumbai”}

September 2000XML Workshop, IIT Bombay Indexes for XML Path indexes: regular path expressions Value Indexes: locating atomic objects

supplier Building A Path Index name address part subpart name address part supplier partsubpart name supplier address subpart h1 h7 h6 h5 h4h3 h2

September 2000XML Workshop, IIT Bombay Path Index Index summarises path information Each entry: list of pointers to data nodes partsubpart name supplier address h1 h7 h6 h5 h4h3 h2

September 2000XML Workshop, IIT Bombay Using Path Index for Regular Path Expressions (R1) part.name (R2) part.supplier.name (R3) _*.supplier.name (R4) part._*.subpart.name partsubpart name supplier address h1 h7 h6 h5 h4h3 h2

September 2000XML Workshop, IIT Bombay Path Indexes XSet project (Berkeley) Dataguides (Lore, Stanford)

September 2000XML Workshop, IIT Bombay Value Index Useful for comparisons (=, <, etc.) Example: Find supplier whose name is “XYZ”? VIndex(name) addressname address part supplier subpart supplier “XYZ” “ABC”

September 2000XML Workshop, IIT Bombay Other Indexes Text Indexes: Information retrieval style keyword search. Example: Find the suppliers in Mumbai(“address”) Also supports search features like AND, OR, NEAR, etc.

September 2000XML Workshop, IIT Bombay Conclusion Performance improves significantly when indexing is used for query processing (Lore). Performance of the path indexes depends on the type of queries.

September 2000XML Workshop, IIT Bombay References The Lore Project (www-db.stanford.edu/lore) Work done by Dan Suciu ( Data on the Web: Serge Abiteboul, et al.

September 2000XML Workshop, IIT Bombay Indexing of XML Data Raghuraman Rangarajan KReSIT, IIT Bombay.