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Index Approach and Implementation

An index has a name together with four structural components:

1.
the data
2.
the index elements
3.
some annotations associated with the data
4.
some header information

Each index has a header file that contains information such as where to find the data, where to find the index elements, where to find the annotations, the type of the data being indexed.

Each index entry contains a reference to the data, the time it arrived at the recorder, and a reference to some meta-data annotations, which will initially be empty. At the end of a recording, each source will have a stream of data and a stream of index entries (called the index track). This is shown in figure 9.8.


  
Figure 9.8: The structure of an index element
\begin{figure}
\centerline{\psfig{figure=pix/index-elem.idraw}}
\end{figure}

Each annotation in the annotation list is an attribute-value pair, where the attribute is a name and the value is any data, either text or binary, that is associated with the particular index element. Each element of the attribute list contains the following data:

  • the total number of bytes in the attribute.

  • some status information, such as ACTIVE or INACTIVE for the attribute.
  • the number of bytes in the name
  • the name of this attribute
  • the number of bytes in the value
  • the value of this attribute

This structure is show in figure 9.9.


  
Figure 9.9: The structure of an attribute element
\begin{figure}
\centerline{\psfig{figure=pix/attribute-struct.idraw}}
\end{figure}


next up previous contents
Next: Using Indexes For Annotations Up: Indexing Techniques Previous: Indexing Techniques
Jon CROWCROFT
1998-12-03