DDE Services

DDE stands for Dynamic Data Exchange and it is a feature of Windows that allow programs to share information. The Viewer is a DDE server. This means that other programs can send information to the Viewer to be incorporated into the survey data. For example, database information can be incorporated into the surveys and displayed with the plot. The Compass data program "CAVEBASE" uses this feature to transfer data to the Viewer.

This section is intended to be documentation for programmers. If you are not a programmer, you may want to skip this section.

Initiating DDE With The Viewer. The Viewer is a DDE server, which means that other programs are responsible for initiating DDE contact with the Viewer. Here are the DDE conversation specifics:

DDE Data Format. Data is transmitted to the Viewer by "Poking" data as a block of strings. Each string item begins with a "pound sign" (#) character followed by single ASCII command character. Following each command is a series of comma-delimited strings and ASCII numbers. The following command lines are available:

1. #F,<feature name> This item specifies the beginning of a group of feature data items. Features are locations in the cave where some particular attribute can be found. The <feature name> is a string that gives the title for the data. For example, if the data contains the locations of water in the cave, the feature name might be "Water."

2. #R,<feature name>,<Min>,<Max> This item specifies the beginning of a group of feature data items. It is similar to the "#F" data except these items contain numerical values. For example, they could represent the PH of streams in the cave. The <Min> and <Max> values represent the range of the values.

3. #L,<station name>,<value> These items represent the location of individual items in the cave. The location is specified by the station. If the data is part of "#R" data and contains numerical values, the <value> item will contain the data. Other wise, <value> is set to zero.

4. #M,<station name> This data item is used to draw lines between points in the data set. It instructs the program to move without drawing to the location specified by the station name.

5. #D,<station name> This data item is used to draw lines between points in the data set. It instructs the program to draw a line between the last location and the location specified by the station name.

Once a data block has been transmitted, the data appears as feature in the Complex window.