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2.4.1 Binding

   As with most objects, only the data part is stored when the document is 
   saved.  The data is stored in the OpenDoc storage system Bento.  A part 
   handler on the other hand is loaded into the memory only once, although it 
   may be used by several active objects of the same kind.  Therefore, there 
   must be a binding process to associate the data part with the right part 
   handler at the documents loading time as shown in Figure 22. 


 


                                              



 
   Figure 22. OpenDoc Binding 

   To define those associations, OpenDoc provides a notebook in the OpenDoc 
   folder called Part Editor Preferences, where part editor associations can 
   be defined for different component kinds (see Figure 23).  It can also 
   define preferred editors for component categories (see Figure 24). 

   OpenDoc provides a six step sequence for that binding process.  OpenDoc 
   uses a special service class ODBinding to make the right decision. 
   OpenDoc maintains a table that maps data types to the part handler. This 
   is defined with another service class, ODNameSpace.  (For class 
   relationship, seeFigure 47 in topic 2.7.5.)  The binding is done in a 
   recursive way, starting with the topmost container part of the document 
   hierarchy, which then invokes the binding for its embedded parts. 


 


                                              



 
   Figure 23. Part Editor Preferences for Kinds 

   This binding is done from OpenDoc in the following order: 

   1.  ODBinding starts to look for a part handler by checking whether there 
       is a preferred editor for this kind specified, as shown in Figure 23. 
   2.  If no preferred editor was specified, it looks for the part editor 
       with which the part was created. 
   3.  If such an editor is not available, it looks for any installed part 
       handler supporting this part kind. 
   4.  Then it looks for another part handler of the same category which can 
       work with the data type the part has stored its data with. 
   5.  Then it looks whether there are translations supported by a special 
       object ODTranslation to another data type understood by a part handler 
       available. 
   6.  If nothing is available, it binds the part to an editor as a last 
       resort.  This editor will show the part as a black box, so a user can 
       work with the rest of the document. 


 


                                              



 
   Figure 24. Part Editor Preferences for Categories 

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