Binary Field Exchange works by describing each type of media file to be analyzed in a Notes form, listing the various values stored in binary fashion within it. Using this method, the description of a .GIF image is displayed in Figure A. In this example, there are certain fields, displayed in green, which are fixed for all image media: ImageWidth, ImageHeight, BitsPerPixel and Version.

FIGURE A


A Binary Field Exchange descriptor for .GIF files. Roll over picture for a larger image.

Additional custom fields are displayed in dark magenta: PaletteScope and Palette Type. For images only, a third value -- BitsPerPixel Offset -- is used to accommodate different ways of calculating total colors from BitsPerPixel (e.g., 1 for .GIF and 0 for .BMP).

This descriptor obviates the need for any LotusScript programming, and allows a Notes media library to intelligently deal with the media it stores while being adaptable to new media formats. The attributes derived from each file can be held as Notes views, and so you can easily find the 32x20 image required for a particular page, or find all the 16 color files. Currently text, numeric and hexadecimal values can be specified, and an optional Binary Mask is available for values that are stored as ranges of bits inside bytes. This should be sufficient to cope with most simple binary file values.

Agent automation
If you have 1,200 images stored in various disk directories, filing them all within Notes isn't going to be the most attractive of propositions. That's where LotusScript agents come into their own. Using the various methods of file access available to them -- direct file system, native Notes databases and Internet protocols -- Notes can read large quantities of files, analyze, and catalogue them.

The free Domino Media Library contains three such agents, which allow you to quickly transfer files from Notes databases, existing Web sites, or from a local disk or network shared file system. All of these methods will use Binary Field Exchange, where appropriate, to retrieve extended information on each file found.

Here are the three agents:

• File System Grab: you will be prompted for a file directory, and a wildcard to select files (e.g., *.GIF). If the *.* wildcard is used to ask for all files, only media with file extensions registered in the database will be loaded.

• Notes Grab: you will be prompted for a server name ("Local" if running from your workstation) and a database name or wildcard. Supplying a wildcard will result in all databases to which you have at least reader access on that server being scanned for file attachments.

• Web Grab: only a single URL is required. All files with a registered file extension will be downloaded, analyzed and stored in the library.

Web agents
The final advantage you can derive from storing media in a Notes database is that access to the images can be made directly via HTTP, either using the standard Domino URL commands to point to the file (e.g., ?OpenElement), or by using Web agents.