The DEAT Business Rule Pattern Language
Russell R. Hurlbut, Ph.D.
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Rule Pattern 33: Protocol
Problem – Describing the Formal Syntax for Cooperating
Business processes rely of automated support that requires collaboration among
components. In order for the components to properly communicate, formal syntax
in terms of information exchanged must be established.
Protocol is established through definition of interfaces that prescribe an
ordered sequence of arguments, types, and defaults. Specifications for each
message exchanged, including return status and exception conditions are provided.
Each argument is defined in terms of a parameter which provides the default
value, the direction (in, out, or both ways), and the classifier type. The format
chosen should conform to industry standards in order to provide the greatest
degree of flexibility. The Protocol business rule pattern recognizes the importance
of interface specifications. Such specifications are a major area of interests
for consortiums of vendors. The nature of protocols is well understood and is
included here for completeness. The examples provided here name two important
interface specifications. Specific examples conforming to these interfaces can
be found in those documents.
Example – Interface Definition Language
The Object Management Group's Common Object Request Broker Architecture Version
2.1 specification provides for a complete interface description through its Interface
Definition Language (IDL). A formal grammar is used for specifications that consists
of one ore more type definitions, constant definitions, exception definitions,
and module definitions.
Example – Workflow Application Programming Interface
The Workflow Management Coalition Workflow Client Application (Interface 2) specification
version 1.2 provides a mechanism for applications to access services of workflow
engines using a consistent interface. A complete set of data types, attributes,
and return codes are defined. Mappings to IDL bindings are also included.
UML Representation and Related Patterns
The Protocol business rule pattern maps to the Argument model element associated
with an Action. The Protocol specifies the ordered list of Arguments attached
to an Action. The Action in turn dispatches a Request that provides the specification
for a MessageInstance.
UML Representation of Protocol Pattern
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