Assembly Descriptor Syntax

The assembly descriptor has the following structure:

assembly sname
   {
   .category = text
   .description = " text "
   .console = " subord-name "

   input  sname
   output  sname
   ...

   property  sname &nbsp[ : dflt = value ]
   property  sname &nbsp[ : mandatory ]
   ...
   volume sname

   subordinate  sname
      {
       .class = clsname
        attr = val
       ...
      }

   connections
      [
       sub-name . trm-name => sub-name . trm-name
      ....
      ]
   visual
      {
      ...
      }
   }

The following attributes are defined for assemblies only, they have no meaning in simple components:

The following attributes are defined for an assembly; they have the same meaning as their counterparts for a simple component:

The order of entities in the assembly is not important and all of the sub-entities are optional, except that an assembly must have at least one subordinate entity.

Here is a summary of the sub-entities of the 'assembly' entity, followed by sub-sections defining each one in detail:

input, output

The terminal entities support a single attribute: mandatory . Specifying this attribute means that the terminal must be connected; mandatory terminals will trigger a compilation error in an assembly that includes a component with such a terminal left unconnected. Note that specifying the mandatory attribute for an assembly is not necessary if the subordinate component's terminal to which it is connected is already mandatory.

An assembly can have any number of terminals, except for the top-level assembly of an application, which should have no terminals.

property

volume

subordinate

All attribute names other than the pre-defined ones are considered to be property names of the subordinate component that need to be set to the specified value - this includes the predefined attributes of the subordinate component ( .boot_tout, .migrateable, .server, .standby ), as well as the component-specific properties defined in it by the 'property' or the 'volume' entities (see the component descriptor syntax).

A special type of value is defined indicating that the property is connected to the assembly's boundary: $.name, where name is the name of one of the 'property' or 'volume' entities in the assembly. If a property has to be set to a literal value that begins with the "$." characters, the value must be quoted to ensure that it is not interpreted as a property connection. More than one subordinate property can be connected to the same boundary property and all such properties get the default value from the boundary property definition if none is provided in an outer-scope assembly. The $.name can be used for the pre-defined attributes of the subordinate as well, making them regular properties on the assembly boundary.

The 'subordinate' entity in an assembly also accepts the resource sub-entities mem , cpu and bw , with the same attributes as defined in the Component Descriptor Syntax section.When applied to a subordinate that is a simple component, they override the resource settings in that component. The "override" must remain within the limits of the range defined in the component (i.e., the new range must no wider than the old one and must fit entirely into the old one). When applied to a subordinate that is an assembly, the specified resources are distributed pro-rata according to the relative weight of the resource requirements in each of that assembly's subordinates. If a resource setting for a subordinate assembly causes a component to receive a resource setting that is outside of the min-max range defined for it, an error is reported by the ADL linker.

connections

$. atrm-name => sub-name . strm-name, or

sub-name . strm-name => $. atrm-name.

Both syntax variants are equivalent and mean that the terminal strm-name of subordinate sub-name is to be visible as atrm-name on the assembly (atrm-name must correspond to an input or output entity defined in the assembly). Since an input terminal is a 'network server' and an output terminal is a client, the following rules apply:

• an output can be connected to at most one input
• an input can be connected to any number of outputs (subject only to limitations on the number of clients that the component supports for the specific service)
• an input terminal on the assembly boundary must be redirected to exactly one input of a subordinate compoent
• any number of subordinate component's outputs can be redirected to a single output on the assembly boundary

-- VladM - 25 May 2006