Automatic Generation
of SQLX View
Definitions from ORASS Views
Yabing Chen, Tok Wang Ling, Mong Li Lee
1
Outline
Introduction
 Preliminaries
 Generating SQLX Query Definitions From
ORA-SS Views
 Conclusion

2
Introduction

XML
 The
dominant standard for exchanging data
on the Internet

XML Views
 Exploit
the potential of XML
 Secure the source data
 Provide an application-specific view
3
Introduction (cont.)

Main related work
 In

all these works, the original data are in RDB
SilkRoute [1] [2]


XPERANTO [3] [4]


Two declarative language RXL and XML-QL to define and
query the views over relational data
uses a canonical mapping to create a default XML view from
relational data
Oracle [7], IBM DB2 [8] & SQL Server [6]

provide the ability to export relational data to materialized XML
views
4
Introduction (cont.)

Disadvantage of the main related work
 Ignore

semantic information in source data
For example, ignore the difference between object
class, attribute and relationship in schema
 Cannot
check the validity of designed views
 Difficult to use query languages to define
views

Proprietary language or XQuery
5
Introduction (cont.)

Our approach for XML views


The original data are in XML and then stored in
ORDB
Design valid XML Views [9]




Based on a semantically rich model - ORA-SS
Use query operators, such as selection, drop, swap, join,
etc.
Support more flexible views than related work, such as
swapping views
Transform the designed views into SQLX queries on
ORDB (this paper)
6
Preliminaries

ORA-SS data model


Three concepts: Object class, attribute and relationship type
An object-relational storage for XML

Store each object class with all its attributes into a nested relation
 Store each relationship type with all its attributes into a nested relation

SQLX syntax


An emerging part of the ANSI and ISO SQL standard
XMLELEMENT


Generate an XML element
XMLAGG

Produce a forest of XML elements from a collection of individual elements
7
Preliminaries – Example
Query: List all employees
project
pe, 2, 1:n, 1:n
jno jname
employee
pe
eno ename
Select xmlelement(“employee_list”,
xmlagg(
xmlelement(“employee”,
xmlattributes(e.eno, e.ename)
)
)
)
From employee e
progress
An ORA-SS source schema
Result:
Object relations:
project (jno, jname);
employee (eno, ename);
Relationship relations:
pe (jno, eno, progress);
<employee_list>
<employee eno=“e01” ename=“david”/>
<employee eno=“e02” ename=“paul”/>
</employee_list>
Object-relational storage schema
8
Generate SQLX queries from ORA-SS views

Main idea
 An
object in the view is determined by some
particular objects in the view through the
relationship types involved.
project

jm, 2, 1:n, 1:n
jno
jname

member
mp, 2, 1:n, 1:n
mname jot_title

p ublication

pno p ub_title
publication is determined by member
through relationship type mp
publication has nothing to do with project
member is called the Determined Object
Class (DOC) of publication
mp is called the Determined
Relationship Type (DRT) of publication
9
Generate SQLX queries from ORA-SS views

Main idea (cont.)
 Identify relationship types in the views



Original relationship in the source schema
Derived relationship by projecting existing relation in the ORDB
Derived relationship by joining existing relations in the ORDB
part
Object relations:
supplier (sno, sname);
part (pno, pname);
factory (fno, fname);
project (jno, jname);
employee (eno, ename, (email)*);
Relationship relations:
ps (pno, sno, price);
sf (sno, fno);
spj (sno, pno, jno, qty);
je (jno, eno, progress);
part
ps , 2, 1:n, 1:n
pno pname
pno pname
supplier
ps
sno sname price
spj,3,1:n,1:n
sf,2,1:n,1:n
factory
Drop supplier
project
pj
project
fno fname
spj
fno fname
factory
pj,2,1:n,1:n
pf,2,1:n,1:n
je,2,1:n,1:n
jno jname qty
je,2,1:n,1:n
jno jname total_qty
employee
je
employee
je
*
eno ename email
progress
Source schema
*
eno ename email progress
View schema 10
General rules for generating SQLX
queries from ORA-SS views

Rule Gen 1 for object class along with its
attributes
 Case
 Case
1: DRT is original relationship
2: DRT is derived relationship by projecting
existing relation
 Case 3: DRT is derived relationship by joining existing
relations

Rule Gen 2 for attributes
 Case
1: original relationship attributes
 Case 2: derived relationship attributes
 Case 3: multi-valued attributes
11
Rule Gen 1 (for object class in the view)

Case 1: If the DRT is an original relationship type from
the source schema, then

Directly use the original relationship type to generate the where
conditions in the where clause.
part
pno pname
factory
e.g. je
pj,2,1:n,1:n
pf,2,1:n,1:n
project
pj
fno fname
je,2,1:n,1:n
jno jname total_qty
employee
je
*
Select xmlagg(
xmlelement(“employee”,
xmlattributes(e.eno, e.ename)))
From employee e, je
Where e.eno = je.jno and je.jno = j.jno
eno ename email progress
employee (eno, ename, (email)*);
je (jno, eno, progress);
SQLX expression for employee
12
Rule Gen 1(cont.)
Case 2: if the DRT is a derived relationship type by projecting
existing relation in the ORDB, then


Replace the derived relationship type with its corresponding original
relationship type in the where clause
part
pno pname
factory
e.g. pj
pj,2,1:n,1:n
pf,2,1:n,1:n
project
pj
fno fname
Select xmlagg(
xmlelement(“project”,
xmlattributes(j.jno, j.jname)))
From project j, pj
Where pj.jno = j.jno and pj.pno = p.pno
je,2,1:n,1:n
pj = spj [p, j]
jno jname total_qty
employee
je
*
eno ename email progress
spj (sno, pno, jno, qty)
project (jno, jname)
Select xmlagg(
xmlelement(“project”,
xmlattributes(j.jno, j.jname)))
From project j, spj
Where spj.jno = j.jno and spj.pno = p.pno
13
Rule Gen 1(cont.)
Case 3: If the DRT is a derived relationship type by
joining existing relations in the ORDB, then


Rewrite the where condition with the DRT’S corresponding original
relations in the where clause
part
e.g. pf
pno pname
factory
pj,2,1:n,1:n
pf,2,1:n,1:n
project
pj
fno fname
Select xmlagg(
xmlelement(“factory”,
xmlattributes(f.fno, f.fname) )
From factory f, pf
Where f.fno = pf.fno and pf.pno = p.pno
je,2,1:n,1:n
Replace pf by ps and sf in ORDB
jno jname total_qty
employee
je
*
eno ename email progress
factory (fno, fname);
ps (pno, sno, price);
sf (sno, fno);
Select xmlagg(
xmlelement(“factory”,
xmlattributes(f.fno, f.fname) )
From factory f, ps, sf
Where f.fno=sf.fno and sf.sno=ps.sno and
ps.pno=p.pno
14
Rule Gen 2 (For relationship attributes)

Case 1: If a single valued attribute A belongs to R and R is an
original relationship type from source schema, then

generate an xmlelement function for the attribute A:
xmlelement(“A”, R.A)
part
pno pname
factory
e.g. progress
pf,2,1:n,1:n
project
pj
fno fname
Select xmlagg(
xmlelement(“employee”,
xmlattributes(e.eno, e.ename),
xmlelement(“progress”, je.progress)))
From employee e, je
Where e.eno = je.jno and je.jno = j.jno
pj,2,1:n,1:n
je,2,1:n,1:n
jno jname total_qty
employee
je
*
eno ename email progress
View schema
SQLX expression for employee
15
Rule Gen 2 (cont.)

Case 2: If an attribute A belongs to R and R is a derived relationship
type by projecting an original relation R’ in the ORDB, then

Generate an xmlelement function for the attribute A with agg function:
xmlelement(“A”, agg(R’.A))
 Append a group by clause for the agg function (e.g. total_qty)
(e.g. total_qty)
part
pno pname
factory
pf,2,1:n,1:n
project
pj
fno fname
Select xmlagg(
xmlelement(“project”,
xmlattributes(j.jno, j.jname),
xmlelement(“total_qty”, sum(spj.qty))))
From project j, spj
Where spj.jno = j.jno and spj.pno = p.pno
Group by j.jno, j.jname
pj,2,1:n,1:n
je,2,1:n,1:n
jno jname total_qty
employee
je
*
eno ename email progress
View schema
SQLX expression for project
16
Rule Gen 2 (cont.)

Case 3: If an attribute A is a multi-valued
attribute in the ORDB, then
 Generate
(e.g. email)
part
pno pname
factory
pj,2,1:n,1:n
pf,2,1:n,1:n
project
pj
fno fname
an sub query to extract the value of A
je,2,1:n,1:n
jno jname total_qty
employee
je
*
eno ename email progress
View schema
Select xmlagg(
xmlelement(“employee”,
xmlattributes(e.eno, e.ename)
(select xmlagg(xmlelement(“email”,
email))
from table(e.email)
))
From employee e, je
Where e.eno = je.jno and je.jno = j.jno
SQLX expression for employee
17
The SQLX query for the whole view example
Select
//generate root & part
xmlelement(“root”,
xmlagg(
xmlelement(“part”,
xmlattributes(p.pno, p.pname),
(Select
// generate factory
xmlagg(
xmlelement(“factory”,
xmlattributes(f.fno, f.fname) ) )
From factory f, ps, sf
Where f.fno = sf.fno and sf.sno = ps.sno and
ps.pno = p.pno
),
(Select
// generate project
xmlagg(
xmlelement(“project”,
xmlattributes(j.jno, j.jname),
xmlelement(“total_qty”, sum(spj.qty)),
(Select xmlagg( // generate employee
xmlelement(“employee”,
xmlattributes(e.eno, e.ename),
(select xmlagg(xmlelement(“email”,
email))
from table(e.email)
)
xmlelement(“progress”, je.progress)
)
)
From employee e, je
Where e.eno = je.jno and je.jno = j.jno
)
)
)
From project j, spj
Where j.jno = spj.jno and spj.pno = p.pno
Group by j.jno, j.jname
)
)
)
From part p
18
Algorithm

Use a deep-first search algorithm to generate
the SQLX query for the ORA-SS view
1.
2.

Generate the SQLX query based on the view
schema (with derived relationship types, etc)
Replace each derived relationship type by using the
corresponding relations in the ORDB
For swapping and selection relationship types,


They refers to the same relations in the ORDB
For selection operator, append the selection
condition in the SQLX query
19
Conclusion

Main contribution
 An
approach to automatically generate SQLX query
definitions of ORA-SS views


Remove the need for users to manually write complex SQLX
view definitions
Main difference between this paper and ER’03
paper [10]

The storage of XML data



In ER’03: Text file
In this paper: ORDB
Semantics of ORA-SS views (relationship in the views)


In ER’03: Do not utilize the semantics
In this paper: Utilize the semantics (e.g. DRT & DOC)
20
References
[1]M. Fernandez, W. Tan, D. Suciu, “Efficient Evaluation of XML Middleware Queries”, ACM SIGMOD,
pp. 103-114, 2001.
[2] M. Fernandez, W. Tan, D. Suciu, “SilkRoute: Trading Between Relations and XML”, World Wide
Web Conference, 1999.
[3] M. Carey, J. Kiernan, J. hanmugasundaram, et. al., “XPERANTO: A Middleware for Publishing
Object-Relational Data as XML Documents”, VLDB, pp. 646-648, 2000.
[4] M. Carey, D. Florescu, Z. Ives, et. al., “XPERANTO: Publishing Object-Relational Data as XML”,
WebDB Workshop, 2000.
[6] Microsoft Corp. http://www.microsoft.com/XML.
[7] Oracle Corp. http://www.oracle.com/XML.
[8] IBM Corp. http://www.ibm.com/XML.
[9] Y.B. Chen, T.W. Ling, M.L. Lee, “Designing Valid XML Views”, ER Conference, 2002
[10] Y.B.Chen, T.W.Ling, M.L.Lee, “Automatic Generation of XQuery Definitions from ORA-SS Views”,
ER Conference 2003.
[11] Y.Y.Mo, T.W.Ling, “Storing and Maintaining Semistructured Data Efficiently in an Object-Relational
Database”, WISE Conference, 2002.
[12] SQLX. http://www.sqlx.org
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