Archives / 2008 / January
  • Technorati Support - Color me impressed

    Who is playing with the London Symphony Orchestra? Come on people, somebody ordered the London Symphony Orchestra... posssibly while high. Cypress Hill, I'm looking in your general direction.

    When I moved my blog what seems like a while ago now, Technorati indexing broke. Today I finally decided to do something about it.

    After reading the FAQs and making sure it wasn't a problem here I emailed Technorati. Less than 20 minutes later they had read my email, fixed the issue, re-indexed this blog and sent a reply.

    Good job Technorati!

  • OpenXML document style inheritance

    The biggest challenge I encountered when writing an object model for OOXML documents was handling inheritance.

    WordprocessingML has a relatively complex inheritance hierarchy (illustrated for the most part in the diagram below) and it was a struggle to come up with a solution that would be both quick to implement for every property across the entire model, and yet be flexible enough to handle every situation and edge case.

    Fortunately I was able to leverage one of my favorite features of OpenXML, property elements, and come up with a quick and (IMO [:)]) simple solution.

    Nelson: Make sure your affairs are in order. Bart: I've set up a trust. It bypasses the inheritance tax. Nelson: Only until 2008. Look into it! 

    Property elements

    OpenXML has a standard approach to defining data and meta-data for an element. Rather than embedding information in attributes directly against the element, OpenXML's approach is to separate the information into a child properties element. For example a run element (<r>) has its data defined in a run properties element (<rPr>), a paragraph element (<p>) has paragraph properties (<pPr>), a table cell element (<tc>) has table cell properties (<tcPr>), etc, etc.



        <w:b />

        <w:szw:val="52" />

        <w:rFontsw:ascii="Cambria" />


      <w:t>OpenXML document style inheritance</w:t>


    Property elements are reused throughout the specification. Run properties for example can be defined directly against a run like the example above, but can also appear in a style element and in the document itself as the document defaults. The appearance of a piece of text is then determined by looking at this hierarchy properties and using the first value it encounters, from direct formatting first to document defaults last.

    Inheritance solution

    I found the property element approach quite beneficial when writing an object model. Reusing property classes was one benefit but I also found the approach useful when implementing inheritance.

    Since the hierarchy is made up of the same object repeated in different places, e.g. run properties directly against a run, run properties on a style, document default run properties, I simply wrote a method which took a delegate for getting a value from the properties object and then ran that against each object in the hierarchy until a non-null value was returned.

    public T GetValue<T>(Func<RunProperties, T> valueGetter)


      // execute delegate against each RunProperties

      // in inheritance hierarchy until a value is returned



    public Unit? FontSize


      get { return GetValue(p => p._fontSize); }

      set { _fontSize = value; }


    So far this solution has worked well for me and it has handled the various edge cases in OOXML.