C H A I M S: Compiling High-level Access Interfaces for Multi-site Software Towards the Science of Component Engineering

The CHAIMS Data types

Control flow and Boolean expressions

The CHAIMS primitives

The CHAIMS Data types

• Integer (basic type)
• Boolean (basic type)
• String (basic type)
• Datablob (complex type)

Elements of type Datablob are exclusively used as user data (i.e. megamodule data) and are not modifiable. Datablobs are transferred between megamodules, no processing of such data is done in the megaprogram.
A datablob is an ASN.1 object which is a nested structure.
• Megamodule_Handle

Elements of type Megamodule_Handle identify a megamodule and allow invocations on that module.
• Invocation_Handle

Elements of type Invocation_Handle identify an invocation and allow additional actions on that invocation.
• Invocation_Status (enum)

Invocation_Status can currently be any of {DONE, NOT_DONE}. Its value is used to describe the actual state of an invocation.

Control flow and Boolean expressions

WHILE

• Purpose

The While loop is a control mechanism used before making invocations which depend on termination of previous event(s).
 

• Syntax

WHILE ( Boolean Expression)  Statement_list

IF

• Purpose

The If statement is a control mechanism used before making invocations which depend on the value of previous result(s).

• Syntax

IF (Boolean Expression) THEN Statement_list
[Else Statement_list ]
 

Boolean expressions

Boolean expressions include:
• Boolean variables
• Equality test between integers, strings and booleans  (a == b)
• Comparison test between integers and strings (a<b, a>b, a<=b, a>=b)

The CHAIMS primitives

SETUP

• Purpose

The SETUP call establishes communication with a designated megamodule.
 

• Syntax

moduleID = SETUP (<megamodulename>)
 

• Parameters' types and descriptions

 
Input:
megamodulename is a string.
It is the name of the megamodule as it is registered in the CHAIMS repository by the megamodule wrapper.

Output:
moduleID is a megamodule_handle.
It is an identifier for the connection. Future invocations to the megamodule designated by megamodulename are specified using moduleID (see other CHAIMS calls below). As any megamodule_handle, it is automatically set by CHAIMS.
 

SETATTRIBUTES

• Purpose

The SETATTRIBUTES call is used to establish any global parameters that are not invocation specific.
 

• Syntax

moduleID.SETATTRIBUTES (<parameter1_name> = <parameter1_value>,
                       <parameter2_name> = <parameter2_value>,
                                                                .....
                                                                <parameter_n_name> = <parameter_n_value>)

moduleID is the connection identifier established by a previous call to SETUP.
 

• Parameters' types and descriptions

 
Input:
(<parameter1_name> = <parameter1_value>,
 <parameter2_name> = <parameter2_value>,
    .....,
   <parameter_n_name> = <parameter_n_value>) is a list of expressions "<paremeter_i_name> = <parameter_i_value>", where 1<= i <= n with i and n integers, and parameter_i_name is a string and parameter_i_value is any of {boolean, integer, string, datablob variable}.  From now on such a list will be called <parameter_value_list>.

parameter_i_names are global attributes of the megamodule identified by moduleID.
There is no order required in the parameter list for the SETATTRIBUTE call.

Output:
None.

 

GETATTRIBUTES

• Purpose

The GETATTRIBUTES call returns the values of the global attributes of the megamodule.
 

• Syntax

objectAttributes = moduleID. GETATTRIBUTES ()
 
 moduleID is the identifier for the connection established by a call to SETUP.
 

• Parameters' types and descriptions

 
Input:
None.

Output:
objectAttributes is a <attribute_value_list> which is identical to the <parameter_value_list> set in the SETATTRIBUTE primitive.
 

ESTIMATE

• Purpose

The ESTIMATE call returns an estimation of the would-be cost of a specific method invocation.
 

• Syntax

value = moduleID.ESTIMATE (<methodname>)

moduleID is the module identifier created by the SETUP call.
 

• Parameters' types and descriptions

 
Input:
<methodname> is a string literal.
It is the name of the method in the megamodule that the megaprogrammer wishes to use. In the case of megamodules that offer one service only, this may be the name of the megamodule itself.

Output:
value is an integer.
It gives the cost in time (seconds) that would generate the invocation of <methodname>.
 

 INVOKE

• Purpose

The INVOKE call starts the execution of a specified method.
 

• Syntax

invokeID = moduleID.INVOKE (<methodname>, <parameter_value_list> )

moduleID is the module identifier created by the SETUP call.
 

• Parameters' types and descriptions

 
Input:
<methodname> is a string literal.
It is the name of the method in the megamodule that the megaprogrammer wishes to use. In the case of megamodules that offer one service only, this may be the name of the megamodule itself. This argument is required in the INVOKE call, and must be first in the argument list.

<parameter_value_list> is defined in the exact same manner as the parameters to SETATTRIBUTES shown above. There can be as many arguments declared as the megamodule wrapper or native CHAIMS megamodules will support. As with the SETATTRIBUTES call, order of the input arguments is irrelevant as long as they follow methodname.

Output:
invokeID is an invocation_handle.
It is an identifier for the invocation. Future calls to EXAMINE and TERMINATE will refer to this identifier so that the correct process is identified. As any handle, it is automatically set by CHAIMS.

 

EXAMINE

• Purpose

The EXAMINE call is used to determine the state of the invocation referred to by invokeID.
 

• Syntax

status = invokeID.EXAMINE ()

invokeID is the invocation identifier assigned in the INVOKE call above.
 

• Parameters' types and descriptions

 
Input:
None.

Output:
status is of type Invocation_Status.
It is an object that holds the result of the examine call. This can be any of {DONE, NOT_DONE}.
 

EXTRACT

• Purpose

The EXTRACT call collects the results of an invocation within an object. It is presumed this will generally be an ASN.1 object (datablob).
 

• Syntax

extract_output = invokeID .EXTRACT ()

invokeID is the invocation identifier assigned in the INVOKE call above.

 
• Parameters' types and descriptions

 
Input:
None.

Output:
extract_output is a datablob.
It is the object that holds the result of the invocation.
 

 

TERMINATE

• Purpose

The TERMINATE call kills either a running invocation or a connection to the megamodule.
Killing a connection to a megamodule kills all the running invocations within this megamodule as well.
 

• Syntax

moduleID.TERMINATE ()  ~OR~
invokeID.TERMINATE ()

moduleID is the identifier for the connection established by a call to SETUP.
invokeID is the identifier for an invocation established by a call to INVOKE.
 

• Parameters' types and descriptions

 
Input:
None.

Output:
None.
 

GETPARAM

• Purpose

Get the data structure of a certain parameter.
 

• Syntax

param_data = moduleID.GETPARAM (<methodname>, <parametername>)
 

• Parameters' types and descriptions

 
Input:
methodname is a string literal.
It is the name of the method in the megamodule that the megaprogrammer wishes to use. This argument must be first in the argument list.

<parametername> is a string.
It specifies the name of the parameter for which we need a default datablob (see below).

Output:
param_data is a datablob.
It is a default datablob containing the names, types and default values of all the attributes of the parameter whose name is <parametername>.

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db 6/16/98