Hi Karthick,
Please find the answers below:
Cardinality: The cardinality defines how often a node is to be instantiated at runtime u2013
that is, how many elements of this node are available at runtime.
u25CF 1u20261
Only one element is instantiated.
u25CF 0u20261
At runtime, no more than one element is instantiated, but it is also possible that no
element is instantiated.
u25CF 1u2026n
n elements can be instantiated, but at least one element must be instantiated.
u25CF 0u2026n
The number of instantiated elements of the context node can vary.
Example:
The context node "Vehicle" is used to describe the fleet of a car rental company. It has the
cardinality 1u2026n and is filled from a database table. A number of attributes of this node have a
specific value for each vehicle.
The database table indicates that the company owns three vehicles, each with unique
registration dates and unique license plate numbers. Thus, to display this table in the Web
Dynpro application, 3 elements of the context node Vehicle must be instantiated; the
cardinality of the node must therefore be 0u2026n or 1u2026n. (If the Vehicle node is to be filled with
values in the context of another function u2013 for example, from a table of all currently available
cars u2013 the cardinality 0u2026n should be used since this table could very easily be empty u2013 that
is, if all cars are rented out.)
*The u201CSingletonu201D Property:*
For each customer of a car rental company, the two attributes u201Crented fromu201D and u201Crented tillu201D
are listed in the context. At runtime, the context then contains the additional relevant values:
If each customer has multiple addresses, it may be necessary to include a child node for the
addresses below the Customer child node. In this manner, the data content of a root node
can rapidly become very large if, at runtime, all customers are displayed with all their
addresses for each vehicle of the of the car rental company. _*To limit the content of a context*_
_*node at runtime, the context node can be assigned the u201Csingletonu201D property*. As a result, the_
_elements of the relevant node are instantiated for only one element of the parent node._
_In other words:_Unlike the cardinality of a node, which describes the number of possible elements within the
node, the u201Csingletonu201D property determines whether or not these elements are set for all
elements of the parent node (non-singleton) or for exactly one element of the parent node
(singleton).
The elements of the child node Customer are only available to one element of the parent
node Vehicle and not to all other elements. However, if you want to instantiate the elements
of the Customer node for all vehicles, you must remove the singleton property for the
Customer node.
*Lead Selection*:
At runtime, every child node set as a singleton contains the elements for exactly one element
of the parent node. For this purpose, one element from the set of possible elements of the
parent node must be highlighted. This is achieved by initializing lead selection. For each
newly created context node, lead selection is initialized automatically, but this setting can also
be deactivated. However, lead selection must generally be initialized for every context node.
u25CF Using the preset automatic initialization of lead selection:
In this case, the first element of a node is always assigned the lead selection
property.
u25CF Manual initialization of lead selection:
If the automatic initialization was deactivated, the lead selection must be programmed
manually. However, in this case it is possible to assign this property to an element
other than the first element of a node.
For the above example, this means:
The singleton property of the context node Customer specifies that the elements of this node
are only instantiated for one of the three vehicles at runtime u2013 that is, the element that bears
the lead selection. Since the lead selection was initialized automatically, this is the first
element of the Vehicle node, which in this case is the element Red Car. However, it would
also have been possible to manually set lead selection for one of the other two elements (for
example, using an index).
Edited by: Vinay Kumar Amruth on Jun 26, 2009 8:00 AM
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