Oracle XDB, Release 9iR2

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Oracle XDB, Release 9iR2
Prepared for IT620 January 20 , 2003
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Talk Outline

• Background
• Key Advantages
• XMLType
• Using XML DB
• Pointers to More Information

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Background

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So far we covered

• 1 Tian, F., DeWitt, D. J., Chen, J., Zhang. C.,
  Design and Performance Evaluation of Alternative
  XML storages
• 2 Shanmugasundaram, J., Tufte, K., Zhang, .,
  He, G., DeWitt, D. J., Naughton, J. F.,
  Relational Databases for Querying XML Documents
  Limitations and Opportunities, VLDB 1999.
• 3 Bohannon, P., Freire, J., Roy, P., Simeon,
  J., From XML Schema to Relations A Cost-based
  Approach to XML Storage, ICDE 2002.
• 4 Tatarinov, I., Ives, Z. G., Halevy, A. Y.,
  Weld, D. S., Updating XML, SIGMOD 2001

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A look at Oracle XDB

• How Oracle has responded to supporting XML?
• Enhancements to Oracle RDBMS
• Additional tools/utilities

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What is Oracle XDB?

• Oracle XDB refers to set of features in the
  Oracle Server for XML. It includes
• A high performance XML storage and retrieval
  technology (based on W3C XML data model)
• New standard access methods for navigating and
  querying XML

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Oracle XDB Key Benefits

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Benefits

• Prior to Oracle XDB
• Structured Data stored in Tables
• Unstructured Data stored as files or BLOBs
• With Oracle XDB
• Both structured and unstructured data stored
  based on standard W3C XML data model.
• Provides complete transparency and
  interchangeability between XML and SQL metaphors
• Allows XML operations over table
• Allows SQL operations over XML documents

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Benefits

• SQL operations over XML documents include
• Piecewise updates
• Indexing
• Search
• Multiple views on data

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Benefits

• XML Repository
• Allows centralized management of content such as
  collection of purchase orders/insurance claims, a
  large technical manual, etc.
• Allows organizing and annotating the content via
  foldering
• Allows maintaining relationships between pieces
  of the content
• Provides Access Control, FTP, and Web-based
  Distributed Authoring and Versioning (WebDAV)
  protocol support with versioning
• XML documents can still be manipulated with file
  abstractions even though stored in Oracle RDBMS

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Benefits

• XML DB provides high performance and scalability
  for operations on complex XML documents.
• XML DB enables data and documents from disparate
  systems to be accessed (via gateways and external
  tables)

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XMLType

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XMLType

• A Oracle supplied type that can be used as a
  columns datatype
• XMLType column supports two storage options
• Unstructured Storage using Large Objects (LOBs)
  or files maintains accuracy of the original XML
• Structured storage maintains Document Object
  Model (DOM).
• Hybrid storage

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XMLType

• Maintains DOM fidelity by enhancing Oracle SQL
  object support. The native extensions include
• Supporting ordering of child elements and
  attributes
• Distinguishing elements and attributes
• Supporting declaring unstructured content in
  schema (contentmixed or ltanygt)
• Supporting undeclared data in instance of a XML
  document, such as processing instructions, etc.
• Supporting enumerated lists
• Native XMLTYPE instances contain hidden columns
  to hold extra information, which can be accessed
  via APIs such as extract

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XMLType Storage

• XMLType column can be changed from one storage to
  other via SQL Export/Import Utility.
• Applications will still work the same.

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Conceptual XMLType Model

• XMLType, which represents a XML document is
  viewed as collection of
• Elements and attributes
• Elements in turn can be
• Complex types consisting of elements and
  attributes
• Simple types consisting of scalar values

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Mapping XMLType to Structured Storage

• Complex type maps to an Oracle Object type
• Each child element and attribute defined by the
  complexType maps to an attribute of the SQL
  object type.
• If a child element in the complexType is itself a
  complexType, the datatype of the corresponding
  SQL attribute will be the appropriate SQL Object
  type.
• If the child element is a simpleType or
  attribute, then the datatype of the corresponding
  SQL attribute will be a primitive SQL data type.

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XMLType Structured Storage Options (for
collections)

• CLOBS. If a complexType is defined with
  xdbSQLTypeCLOB
• Inline VARRAYS. Default. Stored as as a set of
  serialized objects in-line as part of the SQL
  object for the parent element
• Nested Object Tables. The members of the
  collection are stored in a nested object table.

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XMLType Structured Storage Options (for
collections)

• Separate XMLType Table. The members of the
  collection are stored as a separate XMLType
  table. The Parent SQL object contains an array of
  refs. All datatype is XML
• Creating multiple XMLType columns
• Linking from a child to corresponding parent
• Separate XMLType Table with Link Table. The
  members of the collection are stored as a
  separate XMLType table. An link table is created
  which cross references which member in the child
  table are linked to which members of the parent.

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XMLType Benefits

• XML Schema SupportAllows W3C standard XML schema
  based generation of tables and types
• XPath Search Specify elements to query via Xpath
  expressions. Can be combined with other SQL
  (conform to emerging ANSI SQLX standard)
• XPath Indexes Use XPath to specify part of
  document to be indexed to speed up XPath searches
• XML Piecewise UpateAllows identifying individual
  elements and attributes for update via XPath
  expressions. Piecewise Update performed

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XMLType Benefits

• XML Operators New operators like XMLTABLE (to
  cast a list of nodes returned by XPATH into a
  table), to make XML queries and on-the-fly XML
  generation easy
• XSL Transformation for XMLType Uses XSLT to
  transform XML documents via SQL operators
• XPath Views Create XML views to create permanent
  aggregations of various XML document fragments or
  relational tables

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XMLType Benefits

• Lazy XML Load XMLType provides a virtual DOM it
  only loads rows as they are requested, throwing
  away previously referenced section of documents
  if memory usage grows. Results in high
  scalability for concurrent users dealing with
  large XML documents
• Schema Caching Structural information (e.g.,
  element tags, datatypes, etc.) kept in a schema
  cache. Improves perofrmance and scalability of
  large XML documents, as well as for a large
  collection

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Using XML DB

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Creating XMLType Columns

• Problem Store Purchase Orders marked up in XML
  as a column of a table

CREATE TABLE orders (order_info
XMLTYPE) XMLSCHEMA http//www.oracle.com/xdb/orde
rSchema.xsd ELEMENT Purchase Order
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Creating an XML Schema

• Using XML Schema editing environment using XML
  Spy (see http//www.altova.com for details)
• It allows you to specify annotations with the
  schema that controls mapping of the schema to
  database storage.

ltxsdattribute namecustomerId typedecimal
SQLnamecustomer_id, SQLtypenumber /gt
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Registering an XML Schema

• DBMS_XMLSCHEMA.registerSchema() used to register
  the XML schema

dbms_xmlschema.registerSchema(
'http//www.oracle.com/xdb/orderSchema.xsd',
source)
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Registering an XML Schema

• Registration parses/validates the schema and
  generates needed object types, etc.

CREATE TYPE purchaseOrderItem as
OBJECT() CREATE TYPE purchaseOrderItems as
VARRAY() OF pruchaseorderItem CREATE TYPE
purchaseOrder as OBJECT( customerId
number, customerName varchar2(2000), orderDate
date, shipDate date, Items
purchaseOrderItems )
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Loading XML documents

• Via INSERTs

INSERT INTO orders VALUES(
XMLType( 'lt?xml version"1.0"?gt
ltPO

pono"1"gt
ltPNAMEgtPO_1lt/PNAMEgt


lt/POgt
) )

• Via XML Repository (drag and drop)
• inserted to default table specified as part of
  XML schema definition

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Querying XML documents

• existsNodetests the XMLType instance to see if a
  node matching the specified XPath expression
  exists

SELECT order_info FROM orders WHERE
existsNode (order_info, /PO/PNAME) gt 0

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Querying XML documents

• extractreturns document consisting of an XML
  document fragment with those elements and
  attributes matching the XPath expression

SELECT extract(order_info,/PO/PNAME) FROM
orders Output ltPNAMEgtPO_1lt/PNAMEgt

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Querying XML documents

• extractValuereturns a scalar value corresponding
  to the result of the XPath evaluation on the
  XMLType instance

SELECT extractValue(order_info,/PO/PNAME) FROM
orders Result PO_1 SELECT Count() from
orders WHERE extractValue(order_info,/PO/PNAME)
PO_1 Result 1
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Updating XML documents

• Complete UpdatePerformed by replacing it.

UPDATE orders SET order_info
XMLType( 'lt?xml version"1.0"?gt
ltPO

pono"1"gt
ltPNAMEgtPO_2lt/PNAMEgt


lt/POgt
)
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Updating XML documents

• Path-based Updatecan be specified using
  UPDATEXML SQL function.

UPDATE orders SET order_info UPDATEXML(
order_info,
'/PO/CUSTNAME/text()',

'John)
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Unstructured vs. Structured Storage

• Unstructured
• Fast Storage and Retrieval
• Slower Operations
• Allows great flexibility in handline varying
  content
• Larger memory requirement due to need to
  parse/validate etc.

• Structured
• Incurs shredding/reconstruction overhead
• Faster Operations as directly mapped to
  object-relational storage
• Relies on Object-relational and hence suited more
  for uniform content
• Minimal memory requirement

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Unstructured vs. Structured Storage

• Unstructured
• Can create function-based indexes on Xpath
  expressions or inverted indices
• Update does complete rewrite
• Larger space requirement
• Coarse-grain control

• Structured
• Can create native indexes on columns
  corresponding to attributes as well as inverted
  indices
• Performs piece-wise updates
• Less storage requirement as avoids storing tags
• Fine grain control (subpart can be unstructured)

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For more Information

• Main Page http//otn.oracle.com/tech/xml/doc.html
  
• Oracle9i XML Database Developer's Guide - Oracle
  XML DB, Release 2 (9.2) http//otn.oracle.com/docs
  /products/oracle9i/doc_library/release2/appdev.920
  /a96620/toc.htm

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