Table Multimedia_Tab

Figure B-1, "The Multimedia Schema", shows table Multimedia_tab's structure. Table Multimedia_tab columns are described below:

• CLIP_ID: Every row (clip object) must have a number which identifies the clip. This number is generated by the Oracle number SEQUENCER as a matter of convenience, and has nothing to do with the eventual ordering of the clip.

• STORY: The application design requires that every clip must also have text, that is a storyboard, that describes the clip. Since we do not wish to limit the length of this text, or restrict its format, we use a CLOB datatype.

• FLSUB: Subtitles have many uses -- for closed-captioning, as titles, as overlays that draw attention, and so on. A full-fledged application would have columns for each of these kinds of data but we are considering only the specialized case of a foreign language subtitle, for which we use the NCLOB datatype.

• PHOTO: Photographs are clearly a staple of multimedia products. We assume there is a library of photographs stored in the PhotoLib_tab archive. Since a large database of this kind would be stored on tertiary storage that was periodically updated, the column for photographs makes use of the BFILE datatype.

• FRAME: It is often necessary to extract elements from dynamic media sources for further processing For instance, VRML game-builders and animation cartoonists are often interested in individual cells. Our application takes up the need to subject film/video to frame-by-frame analysis such as was performed on the film of the Kennedy assassination. While it is assumed that the source is on persistent storage, our application allows for an individual frame to be stored as a BLOB.

• SOUND: A BLOB column for sound-effects.

• VOICED_REF: This column allows for a reference to a specific row in a table which must be of the type Voiced_typ. In our application, this is a reference to a row in the table VoiceOver_tab whose purpose is to store audio recordings for use as voice-over commentaries. For instance, these might be readings by actors of words spoken or written by people for whom no audio recording can be made, perhaps because they are no longer alive, or because they spoke or wrote in a foreign language.

  This structure offers the application builder a number of different strategies from those discussed thus far. Instead of loading material into the row from an archival source, an application can simply reference the data. This means that the same data can be referenced from other tables within the application, or by other applications. The single stipulation is that the reference can only be to tables of the same type. Put another way: the reference, Voiced_ref, can refer to row objects in any table which conforms to the type, Voiced_typ.

  Note that Voiced_typ combines the use of two LOB datatypes:

  • CLOB to store the script which the actor reads

  • BFILE for the audio recordings.

• INSEG_NTAB: While it is not possible to store a Varray of LOBs, application builders can store a variable number of multimedia elements in a single row using nested tables. In our application, nested table InSeg_ntab of predefined type InSeg_typ can be used to store zero, one, or many interview segments in a given clip. So, for instance, a hypothetical user could use this facility to collect together one or more interview segments having to do with the same theme that occurred at different times.

  In this case, nested table, interviewsegments_ntab, makes use of the following two LOB datatypes:

  • BFILE to store the audio recording of the interview

  • CLOB for transcript

  Since such segments might be of great length, it is important to keep in mind that LOBs cannot be more than 4 gigabytes.

• MUSIC: The ability to handle music must be one of the basic requirements of any multimedia database management system. In this case, the BFILE datatype is used to store the audio as an operating system file.

• MAP_OBJ: Multimedia applications must be be able to handle many different kinds of line art -- cartoons, diagrams, and fine art, to name a few. In our application, provision is made for a clip to contain a map as a column object, MAP_OBJ, of the object type MAP_TYP. In this case, the object is contained by value, being embedded in the row.

  As defined in our application, MAP_TYP has only one LOB in its structure -- a BLOB for the drawing itself. However, as in the case of the types underlying REFs and nested tables, there is no restriction on the number of LOBs that an object type may contain.