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Eduardo Gutarra. Overview Introduction and Motivation Background The ETL Process The multidimensional model and star schema Issues with my star schema.

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Presentation on theme: "Eduardo Gutarra. Overview Introduction and Motivation Background The ETL Process The multidimensional model and star schema Issues with my star schema."— Presentation transcript:

1 Eduardo Gutarra

2 Overview Introduction and Motivation Background The ETL Process The multidimensional model and star schema Issues with my star schema design Sample MDX queries for my cube

3 Introduction Data warehouses are often used as one of the main components of Decision Support Systems. Data warehouses can be used to perform analyses on different fields as long as there is a lot of data. We want to build a data warehouse on places mentioned in books. Gutenberg Canada Website provides books in Text Files and other formats, free of charge. Barcelona Saint John Montreal

4 Motivation Project is inspired from the LitOLAP project Seeks to apply data warehousing techniques in the domain of literary text processing. Allows a literary researcher answering questions over an authors style, or particularities about book among others. Facilitates the analysis of literary texts to a domain expert.

5 Overview Introduction and Motivation Background The ETL Process The multidimensional model and star schema Issues with my star schema design Sample MDX queries for my cube

6 Data warehouse A data warehouse is a database specifically used for reporting. Populating a data warehouse (DW) involves an ETL process where the data is: Extracted from data sources Transformed to conform the schema of your DW. Loaded onto the data warehouse. Once the DW is populated, Online Analytical Processing (OLAP) can be performed on it.

7 Data warehouse Sales in Store 1 Sales in Store 2 Flat Files ETL Process Datawarehouse OLAP Cube OLAP Cube Tend to be orders of magnitude larger Query response Time is more important Transactional throughput is More important Summarize The data

8 Overview Introduction and Motivation Background The ETL Process The multidimensional model and star schema Issues with my star schema design Sample MDX queries for my cube

9 ETL Process According to Kimball, about 70% of the effort is spent in the ETL Process My project has a Single Data Source Obtain the metadata, and the books separately : : Gutenberg Canada. (index.html) AuthorTitle…Year

10 MySQL English? No Transform to Table Form Transform to Table Form Annotated XML File Structured Table Annotated XML File Yes

11 Book1.xml 21: I have lived in Saint John. 22: This sentence has no place mentioned.... Book1.txt 21: I have lived in Saint John. 22: This sentece has no place mentioned.... Natural Language Processing GATE -- Open-source software for text processing. Gazetteer to determine what words or phrases are a location. Annotates sentences and locations Produces XML file

12 MySQL English? No Transform to Table Form Transform to Table Form Annotated XML File Structured Table Annotated XML File Yes

13 Book1.xml 21: I have lived in Saint John. 22: This sentence has no place mentioned.... Book2.xml 31: This sentence mentions Fredericton and Halifax. 32: This sentence mentions Saint John.... Once the XML file is written we have a process to transform Into a single denormalized table. BookPlaceSentenceFrequency Book1Saint John211 Book2Fredericton311 Book2Halifax321 BookPlaceSentenceFrequency Book1Saint John211 Book1NONE221 Book2Fredericton311 Book2Halifax321

14 MySQL English? No Transform to Table Form Transform to Table Form Annotated XML File Structured Table Annotated XML File Yes

15 Overview Introduction and Motivation Background The ETL Process The multidimensional model and star schema Issues with my star schema design Sample MDX queries for my cube

16 The Multidimensional Model We use the multidimensional model to design the way the data is structured Multidimensional model divides the data in measures and context. Measures: Numerical data being tracked Context for the facts: Data used for to describe the circumstances for which a given measure was obtained.

17 Units Sold Profit Measures 20 $45 Time Product Location Dimensions

18 The Star Schema When we store a multidimensional model in a relational database it is called a Star Schema. ProductIDLocationIDMonthIDUnits SoldProfit ProductIDProduct 1Sardines 2Anchovies 3Herring 4Pilchards LocationIDLocation 1Boston 2Benson 3Seattle 4Wichita MonthIDMonth 1April 2May 3June 4July Fact Table Dimension Table 20 $45 2NF 3NF 2NF

19 Attributes Attributes are abstract items for convenient qualification or summarization of data. Attributes often form hierarchies. TimeIDMonthQuarterYear 1JanuaryQ FebruaryQ MarchQ AprilQ MayQ JuneQ JulyQ AugustQ SeptemberQ OctoberQ NovemberQ DecemberQ JanuaryQ12011 FinestCoarsest Q Q2 x Anchovies x Boston 98

20 SentenceID x PlaceID Frequency Place ID City Country Continent Sentence ID Place ID Frequency Sentence ID Text Sentence # Book Author Occupation PlaceSentence

21 Overview Introduction and Motivation Background The ETL Process The multidimensional model and star schema Issues with my star schema design Sample MDX queries for my cube

22 Issues with the Design PlaceIDCityCountryContinent 40UnspecifiedCanadaNorth America 41Unspecified North America 42Unspecified South America What if the place is a country? What if the place is a continent? Dummy value unspecified can fill in the missing values I live in Canada. I live in North America.

23 Issues with the Design London in England, or London in Ontario? Context required to resolve ambiguity Allocation to partially fix the issue I live in London. PlaceIDCityCountryContinent 33LondonEnglandEurope : : : : 45LondonCanadaNorth America BookIDSentenceIDPlaceIDFrequency / /5 Fact Table Dimension Table

24 Issues with the Design Many to Many relationship between Authors and Books Many to Many relationships are tricky. They can lead to double-counting and other problems. AuthorTitleSentenceIDFrequency ? The Knight of the Burning Pestle11 Fletcher, JohnA Story21 ?A Tale of The Big Mountain31 AuthorTitleSentenceIDFrequency Beaumont, FrancisThe Knight of the Burning Pestle1½ Fletcher, JohnThe Knight of the Burning Pestle1½ Fletcher, JohnA Story21 Beaumont, FrancisA Tale of The Big Mountain3½ Fletcher, JohnA Tale of The Big Mountain3½ Author_1Author_2TitleSentenceIDFrequency Beaumont, FrancisFletcher, JohnThe Knight of the Burning Pestle11 Fletcher, JohnNULLA Story21 Beaumont, FrancisFletcher, JohnA Tale of The Big Mountain31 Additional Attribute Allocation Beaumont, Francis Fletcher, John Beaumont, Francis Fletcher, John

25 Place ID City Country Continent Sentence ID Place ID Frequency AuthorGID AuthorID AuthorName Sentence ID Text Sentence # Book AuthorGID Occupation Dimension Table Bridge Table Outtriger Table Add two tables To the Star Schema

26 AuthorID x SentenceID x PlaceID Frequency Text Authors Sentences Places Sentence ID Book Name Sentence # Place ID City Country Continent Author ID Author Name Occupation DOB DOD Sentence ID Place ID Frequency Author ID 2

27 Overview Introduction and Motivation Background The ETL Process The multidimensional model and star schema Issues with my star schema design Sample MDX queries for my cube

28 MySQL English? No Transform to Table Form Transform to Table Form Annotated XML File Structured Table Annotated XML File Yes

29 OLAP Schema The OLAP Schema file indicates where the fact table and dimension tables are in MySQL. Mondrian creates the OLAP cube from the MySQL back-end. JPivot provides the UI for the OLAP cube OLAP Schema File MySQL

30 MDX Query Language

31 References attributes-with.html attributes-with.html The LitOLAP project: Data warehousing with literature (http://academic.research.microsoft.com/Publication/ /the-litolap-project-data-warehousing-with-literature)http://academic.research.microsoft.com/Publication/ /the-litolap-project-data-warehousing-with-literature Kimball, Ralph; Joe Caserta (2008). The Data Warehouse ETL Toolkit (2nd edition). New York: Wiley. ISBN (http://www.kimballgroup.com/)http://www.kimballgroup.com/ Mosha Pasumansky, Mark Whitehorn, Rob Zare: Fast Track to MDX. ISBN Mosha PasumanskyISBN

32 Data Integration Pentahos Data Integration Tool; Kettle Text file input is the de-normalized table. Lookup/update steps populate dimensions. Final step writes fact table.

33 Algorithm for turning XML to denormalized table. Parse xml file and read a sentence in it. Having the sentence, we then add the sentence to the table of sentences: Check if we have a place in the sentence If there is a place, check whether it is new. If it is a new place, then we add an entry for it in the places table.

34 A Comparison Multidimensional Models More appropriate for OLAP applications. Provides faster query response times Reduce the number of joins Easier understanding of Data MDX (Multidimensional Expressions) Relational Models More appropriate for OLTP, or operational databases Better transactional throughput Reduce redundancies as much as possible. SQL (Structured Query Language)


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