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Property Names

The RTL does no error or valid value checking on the name of a property, other than to ensure that it is 32 characters or less and is composed of printable ASCII characters. Any name at all can be used as a property name. However, there must be some control over property names, and the items that go in the property, or chaos will result.

It is up to the application programmer community to define how the property labels will be used, what they will be called, and what will go in them. The property name should be a short description of what the property is. For example, good names might be ``MAP'', ``LUT'', ``GLL-SSI'', ``MGN-MIDR'', or ``VIEWING GEOMETRY'' (these are only examples, not official names!). If it can be general purpose, make it so, otherwise include the project name in the property name. It is possible to put a version number in the property name if necessary, such as ``MAP V2.0'', but this should be done only if a major revision redefines the existing label items. Label items can be added to an existing property without changing a version number. And if you have a version number in the name, all existing code that wants to find that property will have to be changed to include the version number.

In order to maintain a consistent set of names, a name registry (similar to the one for BLTYPE) has been established for properties. Every property name must be entered into this registry, with a pointer to documentation describing the label items that can appear in the property. If you want to create a new property, simply tell the keeper of the registry what name you want to use and what the label items that make it up are (either explicitly or by referring to a document). The registrar will check for duplicates, approve your request, and enter your name into the registry.

At the present time, the keeper of this registry is the VICAR system programmer.

It is important to note that the name registry system is somewhat voluntary, in that the RTL makes no checks on the validity of the names used. It is the responsibility of each individual programmer to make sure that they use this system. Failure to do so may result in your program not being accepted for delivery.