1 XML INTEROPERABILITY Manjusha Ravindranath

2 CONTENTS Introduction Interoperability XSSQL syntax Usecases document Group By -Without aggregation -With aggregation -Multiple XML Databases Restructuring Queries Implementation Conclusion

3 INTRODUCTION The goal of this research is - to study XML interoperability. - to develop a SQL oriented query language XSSQL for querying XML documents in comparison to procedure oriented languages like XQuery. - to study mapping between the flat representation of relational data and the hierarchical representation of XML data.

4 INTEROPERABILITY Interoperability is the ability to uniformly share, interpret, query and manipulate data across component databases. XSSQL supports main key features of an interoperable language by -being independent of the XML schemas and Document Type Descriptors. -permitting restructuring of one XML document to another through view definition capabilities.

5 XSSQL SYNTAX select {$var/Qname } from document (“doc_name.xml”)//Qname $var where whereConditions Variables are declared in the from clause as - document (“doc_name.xml”)/Qname $var for an element at the top level of the document. - document (“doc_name.xml”)//Qname $var for an element which is at intermediate levels of the document. Group by is given inside the in the select clause as

6 QUERIES FROM USECASES DOCUMENT 1. “XMP” Queries 2. Tree Queries 3. “SEQ” Queries 4. “R” Queries 5. “SGML” Queries 6. ”STRING” Queries 7. “NS” Queries 8. “PARTS” 9. “STRONG”

7 “XMP” QUERY Sample Data-”bib.xml” TCP/IP Illustrated Stevens W. Addison-Wesley Data on the web Suciu Dan Morgan Kaufmann

8 QUERY (XSSQL) Solution in XSSQL Q1. List books published by Addison-Wesley after 1991 including their year and title. select {$b/title} from document(“bib.xml”)//book $b where $b/publisher =“Addison-Wesley” and >1991 Expected Result TCP/IP Illustrated

9 QUERY (XQUERY) Solution in XQuery XQuery uses the “FLWR” expression which consists of FOR, LET,WHERE and RETURN for $b in document(“bib.xml”)//book where $b/publisher=“Addison-Wesley” and >1991 return {$b/title} Solution in XQuery has the same above expected result.

10 TREE QUERY - FUNCTIONS IN XSSQL Sample Data -”book.xml” Data on the web Dan Suciu Introduction Text…. Audience Text…. Web Data and the Two Cultures

11 QUERY (XSSQL) Solution in XSSQL Q2. Prepare a nested table of contents for Book1 listing all the sections and their titles preserving the attributes of each element if any. create function toc ($e as element) return element * as begin { declare $n = local-name($e) if ($n =“section”) select {toc($e/*)} if ($n =“title”) select {$e/text ()} } end { toc(document(“book.xml”)/book) }

12 EXPECTED RESULT Introduction Audience Web Data and the Two Cultures

13 QUERY (XQUERY) Solution in XQuery define function toc ($e as element) as element * { let $n: = local-name($e) return if ($n =“section”) then {toc($e/*)} else if ($n =“title”) then {$e/text ()} else {} } { toc(document(“book.xml”)/book) }

14 GROUP BY In XSSQL the concept is that each node will have its own grouping. Each child will inherit grouping of its parent The cases studied under group by are - Group by without aggregation - Group by with aggregation - Multiple XML Databases Following queries are based on the document “sales.xml”. This document gives the daily sales of the stores in two cities in each month starting from January of the current year. For the sake of simplicity two stores in two cities of NC are taken and sales of couple of days in the months of January and February are discussed.

15 WITHOUT AGGREGATION Sample Data -“sales.xml” NC Greensboro Harris Teeter January NC Greensboro Food Lion January

16 QUERY (XSSQL) Q3. List all stores in each city. select distinct($c/text()) distinct($s/text()) from document (“sales.xml”)/entries/entry $e, $e/city $c,$e/store $s

17 SEMANTICS OF GROUP BY IN XSSQL The instantiations after the group by would be like the following $c $s Greensboro Harris Teeter Greensboro Food Lion Raleigh Harris Teeter Raleigh Lowes

18 SEMANTICS OF GROUP BY IN XSSQL The output instance is graphically shown below. By <city group By $c, $c binds to every … in the document. Duplicate city names are eliminated by distinct ($c/text()). root Gso Raleigh HTFLHTLowes

19 EXPECTED RESULT Greensboro Harris Teeter Food Lion Raleigh Harris Teeter Lowes

20 QUERY(XQUERY) for $c in distinct-values(document(“sales.xml”)//city) return $c/text() { for $e in document(“sales.xml”)/entries/entry where some $ca in $e/city satisfies deep-equal ($ca,$c) for $s in distinct-values ($e/store) return $s/text() }

21 NEW GROUP BY PROPOSAL The above example can be written in XQuery using a new GROUP BY proposal provided by Prof. Dan Suciu. for $e in document(“sales.xml”)/entries/entry, $c in $e/city, $s in $e/store return GROUPBY $c IN $c/text() GROUPBY $s IN $s

22 QUERY (XSSQL) Q4. Give the monthly sales in all stores in each city select distinct($c/text()) distinct($s/text()) distinct($m/text()) SUM($i) from document (“sales.xml”)/entries/entry $e, $e/city $c,$e/store $s, $e/month $m, $e/sales $i

23 EXPECTED RESULT Greensboro Harris Teeter January 210 February 730 Food Lion January 300 February 830

24 QUERY (XQUERY) for $c in distinct-values(document(“sales.xml”)//city), $e in document(“sales.xml”)/entries/entry where some $ca in $e/city satisfies deep-equal($ca,$c) return distinct($c/text()) { for $s in distinct-values(document(“sales.xml”)//store), where some $sa in $e/store satisfies deep-equal($sa,$s) return distinct($s/text()) { for $m in distinct-values(document(“sales.xml”)//month) let $i=$e/sales

25 QUERY (XQUERY) contd... where some $ma in $e/month satisfies deep-equal($ma,$m) return distinct($m/text()) { SUM($i) } }

26 MULTIPLE XML DATABASES Suppose we have multiple XML databases having similar and possibly overlapping data. Sample Data “Univ1.xml” and “Univ2.xml” deals with student information in different majors. Mathematics Stephen Providence Dale Borget Computer Science Barbara McMasters

27 MULTIPLE XML DATABASES Sample Data “Univ2.xml” Mathematics Dale Borget Mary Rierson English Robin Mooney

28 QUERY (XSSQL) define function students ($a as element entry) as xs:string { declare $b =$a/student return $b } select { $e1 / major} { students ($e1)} { $e2[student NOT IN (select $sa from document(“Univ1.xml”)//entry $ea, $ea/major$ma $ea/student $sa where $ma/text()=$m2/text() ) ]/student }

29 QUERY (XSSQL) contd... from document(“Univ1.xml”)//entry $e1, document(“Univ2.xml”)//entry $e2, $e2/major $m2 UNION select {$a} from document(“Univ2.xml”)//entry $a, $n in $a/major where $n not in document(“Univ1.xml”)//entry/major

30 EXPECTED RESULT Mathematics Stephen Providence Dale Borget Mary Rierson Computer Science Barbara McMasters English Robin Mooney

31 RESTRUCTURING QUERIES The following two documents “doc1.xml” and “doc2.xml” contain the same information about company stocks but have a different hierarchical structure. Views have been created to demonstrate the restructuring capabilities of XSSQL.

32 RESTRUCTURING QUERIES Sample Data “doc1.xml” 8/8/03 IBM /8/03 MSFT 6681

33 RESTRUCTURING QUERIES Sample Data contd.. 8/9/03 IBM /9/03 MSFT 6981

34 RESTRUCTURING QUERIES Sample Data “doc2.xml” 8/8/ /9/

35 RULES OF RESTRUCTURING a. /doc2/entries/stock/IBM is a /doc1/entries/stock/ticker b. If x is a ticker then /doc2/entries/stock/x/text() corresponds to /doc1/entries/stock/value.

36 QUERY (XSSQL) create view doc1_to_doc2 as select distinct($d/text() ) $v/text() from document (“doc1.xml”)//stock $s, $s/date $d, $s/ticker $t, $s/value $v Expected Result “doc2.xml”

37 IMPLEMENTATION XSSQL queries are translated into XQuery using naive algorithms. General Algorithm used to translate XSSQL into XQuery: - Read and tokenize input XSSQL string using white spaces (Can use JAVA stringTokenizer classes). - Translate XSSQL tokens to tokens in XQuery using functions. - Finally concatenate XQuery tokens to produce the output string.

38 CONCLUSION In conclusion We introduced XSSQL as a SQL oriented query language for querying XML documents. We developed a formal syntax of XSSQL akin to SQL and provided novel algorithms for translating XSSQL to XQUERY. We have shown that XSSQL extensively deals with group by with and without aggregation in single and multiple XML documents using several levels of nesting. This work leads to many important directions of future work like - optimization of views in XML documents. - merging of multiple (more than two) XML documents. - developing standalone engine for XSSQL.

39 RFERENCES Lakshmanan, L.V.S., Sadri, F., and Subramanian, S.N SchemaSQL- An Extension to SQL for Multi-database interoperability. W3C Working Draft XML Query Use Cases- Cotton, P., Robie, J., - Jan 30, 2002 Querying XML Documents. Unicode Conference Berners-Lee, T., Hendler, J., Lassila, O., - May 17, 2001 The Semantic Web.Scientific American W3C Recommendation, - May 2, 2001 XML Schema Part 0: Primer