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Thread: Mondrian Schema .xml Vs Pentaho metadata domain .xmi Vs CDA .cda

  1. #1
    Join Date
    Mar 2011

    Question Mondrian Schema .xml Vs Pentaho metadata domain .xmi Vs CDA .cda

    I am have been exploring the pantaho ecosystem the past couple of weeks. Please forgive any naive things in the question.

    There are a couple of things about these config files ( containing domains names and its mappings etc ) that I cant seem to put my finger on. Basically I want to understand the relationship if any between the three config files in the title.

    So, if you use mondrian directly, you setup these xml config files. Now, suppose I use Pentaho BI server instead of just plain mondrian, then there are these metadata domain xmi files in the solution repository.

    Q1) Do these pentaho metadata domain xmi files obviate the need for the mondrian schema xml files ?

    Now, also CDA ( community dashboard access ) looks interesting. And if I install this plugin there would be .cda config files in the solution repository. The cda files contain both connection and also domain mapping details.

    Q2) Do these cda files obviate the need to the two config files discussed in Q1 ?

    Q3) Suppose I want to use olap4j to write an mdx query to Pentaho BI server referencing a cda file. Does that question make sense ?


  2. #2
    Join Date
    Jul 2009


    (Q1) Mondrian schema xml files define cubes and dimensions. You submit MDX queries to Mondrian, which translates your MDX into SQL queries on your relational database, where the tables are in a star schema. MDX is very different from SQL, but if you know SQL, you will be able to pick up MDX. It's not easy, but it's very powerful.

    Metadata xmi files define a relational data model on top of relational tables. The tables don't need to be in a star schema.

    Mondrian schema xml files and Metadata xmi files have no relationship to each other. They're different ways of modeling and querying data.

    (Q2) CDA files are like pre-built queries. You can use MDX queries inside a CDA file, but it needs to refer to a Mondrian schema xml file. I don't know if you can use a Metadata query in CDA or not. You can use a direct SQL query inside CDA, however.

    (Q3) You wouldn't use olap4j to write MDX referencing a CDA file. The CDA file has the MDX query defined inside it. The MDX query could be parameterized, so you could submit parameters to it.

    CDA is fairly new. This is an oversimplification, but I think of CDA as a method to separate your query logic from your presentation layer. A SQL expert can build your queries in CDA, and a web designer can build great-looking dashboards and reports that leverage those CDA queries. Or if the same person "wears both hats," you still get the benefit of factoring your BI content into smaller, more manageable, and reusable parts.

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