A categorization of XML technologies based on the kind of rulesthey expr

["Costello, Roger L." <costello@mitre.org>]

Hi Folks,


    Below I categorize some XML technologies 
    based on the kind of rules they express. 
    Following that I describe the importance 
    of making rules explicit (i.e. not buried 
    in code) and assert that the collection of 
    rules for a business define its collective 
    intelligence. I welcome your thoughts.



CATEGORIZATION OF XML TECHNOLOGIES BASED ON THE KIND OF RULES THEY EXPRESS


EXPRESSING PROCESS OR WORKFLOW RULES

I identify four XML technologies for expressing process or workflow rules:

1. BPEL

2. XProc

3. NVDL

4. Schematron

BPEL expresses rules for orchestrating Web services.

XProc expresses rules for processing XML documents.

NVDL expresses rules for partitioning XML documents and dispatching each part to the appropriate validator.

Schematron expresses rules for progressive validation: each <phase> element may map to a step in a process or workflow.



EXPRESSING DATA VALIDITY RULES

I identify four XML technologies for expressing data validity rules:

1. NVDL

2. Schematron

3. XML Schema

4. RELAX NG

Notice that NVDL and Schematron express both process/workflow rules and data validity rules.



EXPRESSING USER INTERFACE RULES

I identify two XML technologies for expressing user interface rules:

1. CSS

2. XForms



EXPRESSING DATA RELATIONSHIP RULES

I identify two XML technologies for expressing data relationship rules:

a. RDF Schema

b. OWL


Here is a diagram showing this categorization:

http://www.xfront.com/Categorization-of-XML-Rules-Technologies.gif


By deploying these XML technologies it externalizes the thinking of an organization.


Note: In the following sections I quote liberally from "Business Rules Applied" by Barbara von Halle.



MAKE RULES EXPLICIT 

Too often the rules are implicit or buried in code. This makes it difficult to change the business. Users and developers are forced to guess and make assumptions. 

Make explicit the rules of the business. This enables you to deliver better changeable systems faster.

Create systems in which the rules are:

- separated from other components so everyone knows *that* they exist

- externalized so everyone knows *what* the rules are

- traceable to their origins and their implementations so everyone knows *where* the rules come from

- deliberately positioned for change so everyone knows *how to improve* them



COLLECTION OF RULES = COLLECTIVE INTELLIGENCE

The collection of rules across an enterprise is its collective intelligence. They determine who an organization is and what it can become. They can be challenged and analyzed. They are the inspiration and primary guidance system for collective behavior. They are the mechanisms by which an organization changes itself.


/Roger