NameSpace - ObjectVision/GeoDMS GitHub Wiki

Tree items often refer to other tree items, in defining units, expressions or other properties. References to other items are configured by name. The referred name means the direct name of the configured item and the relevant parent item names. Which parent item names need to be configured in a reference, depends on the location of the tree item referring to the other items.

If an item is configured in the same context (same parent item) as its referred items, the reference can be configured with only the direct name; no parent item name has to be configured. This also applies to the direct subitems of each of the parents of the item. For items in other branches parent items need to be added to your reference.

Within the GeoDMS items are found in their search path. This path starts in the context of the configured item containing the reference. If the referred item is not found in this context, the parent level of this item is searched, until the root level is reached.

Items configured in side branches are not part of this search path. The GeoDMS needs to be informed about the side branches in which the requested items occur. This can be done by specifying this branch information in the name of the referred items. The relevant parent item names need to be added to the name of the referred item, until the level of a parent item is reached which is part of the search path.

Another way of indicating that a branch, not being a part of the search path, needs to be searched for items is by configuring the Using property.

Assume the following configuration:

container LandUseScanner
{
   container Units
   {
       unit<float32> m   := BaseUnit('m', float32) , label = "meter";
       unit<float32> km  := 1000.0 * m             , label = "kilometer";
       unit<float32> s   := BaseUnit('s', float32) , label = "second";  
       container speed
       {
           unit<float32> m_per_s := m / s, label = "meter per second";
       }  
   }
   container Calc
   {
       parameter<Units/m> dist := 10[Units/m];
       container speed
       {
          parameter<Units/m>             dist    := 50[Units/m];
          parameter<Units/s>             period  :=  5[Units/s];
          parameter<Units/speed/m_per_s> speed50 := dist / Period;
          parameter<Units/speed/m_per_s> speed10 := Calc/dist / Period;
       }
    }
}

This example contains multiple references. The following examples can be derived from this script to illustrate the NameSpace concept of the GeoDMS:

1. Same Container: The km (Kilometer) unit in the Units container contains a reference (within the expression) to the m (Meter) unit. The name used for this reference item is only m, as the m item is configured in the same container (Units) as the km item. This m item can therefore be found and no parent item name is needed.

2. Within Search Path: The m_per_s (meter per second) unit in the Units/speed container contains references (within the expression) to both the m and s items. These m and s items are configured in the Units container. As in example 1, only the direct tree item names are used in the reference, as the Units container is within the search path of the m_per_s item. The full search path for the m_per_s item is:

• first the container speed of the Units container
• second the container Units
• third the container LandUseScanner The m item can be found in the Units container and therefore no parent item name is needed.

3. Parent name needed: The item dist in the Calc container contains two references (in the definition of the values unit and in the expression) to the item m configured in the Units container. The full search path for this dist item is:

• first the container Calc
• second the container LandUseScanner Within this search path the item m is not found. But in the container LandUseScanner the container Units can be found. So in this case the name of the direct parent (Units) needs to be added to the name of the referred tree item (m), resulting in the name: Units/m.

4. Multiple parent names needed: The items speed50 and speed10 in the Calc/speed container contain references (in the definition of the values unit) to the item m_per_s configured in the Units/speed container. The full search path for these items is:

• first the container speed of the Calc container
• second the container Calc
• third the container LandUseScanner Within this search path the item m_per_s is not found. Also the item: speed/m_per_s cannot be found in this search path. But in the container LandUseScanner the container Units can be found. So in this case the name of both parents (Units/speed) needs to be added to the name of the referred tree item (m_per_s), resulting in the name: Units/speed/m_per_s.

5. Adding parent names can result in different outcomes: The items speed50 and speed10 result in outcomes of respectively 10 and 2. Configuring the item Calc/dist or dist does matter in this case. This also relates to the search path for these items (see example 4). In the expression configured for the speed50 item, the dist item is found in the same container (speed). The GeoDMS does not look any further and uses this dist item (with as value 50 Units/m). In the expression configured for the speed10 item, the Calc/dist item is not an item name that can be found in the speed container. But the item name can be found in the parent container, Calc (with as value 10 Units/m). So in the configured expression for these items, references are made to other items based on the parent names added.