About execution procedures

There are a total of ten operations possible on objects. For each operation that is valid for an object class, the OSA handling that class must provide an execution procedure to carry out the operation. Eight of these operations are available through the object API. The first five were introduced above, since they operate on attributes:

• get

• replace

• replace with default

• add

• remove

create

create a new object of the class

delete

delete an object

action

perform a class-specific action. For example, an action available for floppy disks is the "format" action.

filter

filter a list of objects based on the values of their attributes

list

make a list of objects that are contained by another object (containment is described in the next section)

The decisions that need to be made with respect to object operations are as follows:

• For the five attribute operations, you must implement a procedure for the operation if it is a valid operation for any of the attributes. You can choose to implement the procedures in two ways:

  
  per attribute

  the procedure is called for each attribute on each object of the operation. In our example, if someone wanted to get all the attributes for two UUCP system objects, the get procedure would be called twelve times (two objects multiplied by six attributes per object).

  
  per object

  the procedure is called only once for each object, and is expected to handle all attributes for the object in that call. In the example above, the get procedure would only be called twice, once for each object, but would have to return all the requested attributes in each call.