XCube XML for Data Warehouses

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1 XCube XML for Data Warehouses Wolfgang Hümmer Andreas Bauer Gunnar Harde DOLAP 2003 New Orleans

2 Motivation/Outline DOLAP 2002 XML standard for Data Warehouse data is desirable Possible benefits Integration/federation of Data Warehouses Standardize MD data model Data Warehouse Web Service Motivation

3 The Download Use Case Web Cube Data Warehouse cube formulated in XML Web server offers Web Cubes download schema Local DW download dimensions download facts Network Web server Web cubes Motivation

4 The Query Use Case Download case plus selective query Benefit: reduce network traffic Local DW download schema download dimensions query download selected facts Network Web server Web cubes Motivation

5 Further Use Cases The Generating Use Case Create Web Cubes from raw data Create Web Cubes from existing Data Warehouse data Introduction of Standard Dimensions Federation of Data Warehouses Data Warehouse Portal Motivation

6 Requirements for Web Cubes Support for multidimensional model(s) Distinction between Multidimensional schema Dimension/master data Facts/transaction data Flexible: reuse and extensibility Suitable for transport over networks Motivation

7 XCube Collection of XML formats for Describing MD data cubes, i.e. Web Cubes Formulating simple queries on data cubes Goal: exchange of warehouse data Note: XCube is not a (proper) query language! Joint development of OFFIS and FAU Basic formats

8 Overview XCube Formats Basic XCube Formats XCubeSchema XCubeDimension XCubeFact Advanced XCube Formats XCubeText XCubeQuery XCubeFunction Basic formats

9 XCubeSchema Description of MD structure Contains links to Dimensions & their hierarchy levels Facts Extensions Multicubes Data types & unit types Computed facts Inheritance, composition Standard Time Dimension Basic formats

10 XCubeSchema Example <multidimensionalschema> <cubeschema> * <fact> * <dimension> <classschema> * <classlevel> * <rollup> * <attribute> <multidimensionalschema > <cubeschema id="sale"> <fact id="sales"/> <fact id="revenue"/> <dimension id="geography" granularity="branch"/> <dimension id="product" granularity="article"/> </cubeschema> <classschema> <classlevel id="branch"> <attribute id="manager"/> <rollup tolevel="city"/> </classlevel> <classlevel id="city"> <rollup tolevel="region"/> </classlevel> <classlevel id="article"> <attribute id="articlename"/> <attribute id="brand"/> <rollup tolevel="productgroup"/> </classlevel> <classlevel id="productgroup"> <rollup tolevel="productfamily"/> </classlevel> geography product </classschema> </multidimensionalschema> Basic formats

11 XCubeDimension Store data of single dimension Populate classification levels from above Assign units to nodes Special features Shared Roll-Ups Versioning of nodes Reuse & refine standard Time-Dimension Basic formats

12 XCubeDimension Example <dimensiondata version="0.4 > <units><entry unittype="currency" unit="eur"/></units> <dimensiondata> <units> * <entry> <classification> * <level> * <node> * <attribute> * <rollup> <classification> <level id="country"> <node id="germany"/> <node id="switzerland"/> <node id="france"/> </level> geography <level id="region"> <node id="northern Germany"> <rollup tonode="germany" level="country"/> </node> <node id="western Germany"> <rollup tonode="germany" level="country"/> </node> <node id="eastern Germany"> <rollup tonode="germany" level="country"/> </node> <node id="southern Germnamy"> <rollup tonode="germany" level="country"/> </node> </level> </classification> </dimensiondata> Basic formats

13 XCubeFact Stores facts of a data warehouse cube <cubefacts version="0.4 > <cubefacts> * <cube> * <cell> * * <dimension> <fact> <cube id="sale"> <cell> <dimension id="geography" node="branch48"/> <dimension id="product" node="ma-450"/> <dimension id="time" node=" "/> MD coordinates <fact id="sales" value="3"/> <fact id="revenue" value="960"/> </cell> fact values <cell> <dimension id="geography node="branch75"/> <dimension id="product" node="ma-450"/> <dimension id="time" node=" "/> <fact id="sales" value="2"/> <fact id="revenue" value="640"/> </cell> </cube> </cubefacts> Basic formats

14 Short Summary What we have so far XCubeSchema XCubeDimension XCubeFact Result We are able to express a complete data cube in XML Basic formats

15 XCubeQuery Dynamically explore a web cube Not meant to be YAQL Reduce network traffic by drilling down to the area of interest Usability depends on ability of the data source E.g. dumb sources cannot slice & dice Problem treated with XCubeFunction Adv. formats

16 XCubeQuery Sequence (1) <getcubeschema> Get List of Cubes <cubeschema> * <getcubeschema id= > Get facts & dimensions <cubeschema id= > <fact> * <dimension> * Client Server Adv. formats

17 XCubeQuery Sequence (2) <getclassschema> <dimension id= > * Get all information on dimension(s) <class Schema> <classlevel id= > * <datatypes> <datatype name= > * <unittypes> <unittype> * Client Server Adv. formats

18 XCubeQuery Sequence (3) <getfacts> <cube id= > * <dimension id= > * <fact> * Get facts <cube id= > <cell> * <dimension id= node= >* <fact id= value= >* Client Server Adv. formats

19 Further XCube-Standards XCubeFunction Query the abilities of a server holding web cubes Determines to what degree XCubeQuery can be used XCubeText Add textual descriptions/comments In place vs. external file(s) Adv. formats

20 Prototypical Implementation Oldenburg TPC-H data Erlangen XCube-Generator Windows 2000 MS SQL Server & OLAP Services XCube-Loader Solaris 8.0 Oracle 9i TPC-H data Scale Factor Prototype

21 XCube-Loader Metamodel based on CWM Database system independent Pluggable DBS drivers Object structures DB structures XCS Oracle DW 1 Oracle XCD MS Access DW 2 MS Access XCF Driver manager Transformation Prototype DW n

22 Summary XCube Standard formats for formulating cubes Issues No unique MD data model Overhead/size gained by using XML Vision Data Warehouse Web Service Federations of warehouses Summary

23 Thank You for Your Attention Are there any Questions? Find out more at Summary