Business rules are an expression of business policy in a form that is both comprehensible to business users and
executable by a rule engine. From a business perspective, a business rule is a precise statement that describes,
constrains, or controls some aspect of the business.
Let's illustrate this concept with a simple example coming from the lending industry. The following business policy can
be established to limit the loan amount a bank can purchase:
Only prime loans are eligible for purchase
This policy may be split into two implemented rules, one defining what a prime loan is and the second taking the
decision on purchasing it or not.
If the loan amount is less than the prime loan limit, then the loan type is Prime
If the loan type is not Prime then reject the loan
Implementing these rules using an Object Oriented Language may look like two if statements testing conditions on
objects, and applying actions on the same or other objects
if (loan.amount < PrimeLoanLimit) {
loan.type = PrimeType;
}
if (loan.type != PrimeType) {
case = new Case("Loan is not Prime");
loan.status = REJECT;
}
The concept of business rules is not new, and for decades analysts and developers were implementing them within
business applications. What is more recent is the introduction of a Business Rule Management System application which
provides tools to manage the rule as a standalone element, outside of the core business application, and in a form
which is executable by a rule engine.
Business rules are packaged as a Rule Set which can be considered as a piece of software executed by a rule engine.
Integrated in a business application, the rule set implements a sub-set of the business logic. This logic is
externalized from the traditional code and can be easily changed, and maintained by business analysts instead of
developers.
As opposed to business logic embedded and hidden in functions, procedures, macros or databases, business rules are
clearly separated from the rule engine, a software component which executes and activates rules based on matching
conditions on a set of data.
Figure 1 below illustrates this fundamental approach in implementing business logic, with the old embedded model on the
left and the new architecture on the right. In many ways the approach is similar to the separation of code and data
which Data Base Management Systems (DBMS) brought in the 1970s.
A piece of business logic or rule embedded in code will be more
difficult to identify, locate, and change, therefore increases costs of maintenance.
A rule which is externalized in a BRMS platform, and whose versions
are controlled in a rule repository and deployed and executed in a rule engine, will be much easier to modify, thus
reducing dramatically the time and cost to implement changes required by the business.
Traditional software life cycles such as the V cycle or waterfall
model are notorious for leading to systems which costs more than expected, come to market later than planned and with
outcomes not matching the clients' initial expectations. With such approaches, the business users have little ownership
of the solution, and the time required to implement changes can easily range from 3 to 6 months if not more. As a
result, policy owners don't feel comfortable with change which translates into a loss of agility to respond to new
business and competitive situations: too much time passes between policy owners submitting requirements to IT and the
actual deployment of new rules.
Also, with all the fine tuning and iterations, policy owners cannot
really be sure that the policy is being implemented according to their needs. The only way to actually know is to keep
performing tests and hope that all the cases are covered in such tests.
As important element of the business decision, the business rules need strong management processes and tools to support
their life cycle.
A BRMS provides solutions to make this management more efficient, both for developers and for the business users of the
applications. Obviously tooling is not the single answer to the software and business challenges behind the development
of decision-support systems. Deploying BRMS, BRE, and BPM components into business applications requires to modify
current development methodologies and practices in order to take into account new concepts as well as providing a
better collaboration framework between IT and business.
The Agile Business Rule Development methodology corresponds to such a need. It is an incremental and iterative software
development process leveraging the Agile Alliance manifesto (Agile
Manifesto). Here are some of the Agile development values particularly relevant to the implementation of a rule set
using the ABRD approach:
· Individuals and interactions over processes and tools. The rule
discovery, analysis and validation activities require an active and efficient communication between the rule developer
and the Subject Matter Experts (SMEs). Such processes are defined as light as possible.
· Working software over comprehensive documentation. The proposed rule
set development done per iteration, with its validation step, is based on the evidence that a working and executable
rule set has much more business value than a rule description manual. All the project stakeholders benefit from such a
principle but in particular the business users who are then sure that what they see (the rules) is what gets executed
in the deployed system.
· Customer collaboration over contract negotiation. Subject Matter
Experts who define the business policies and the business rules are strongly involved in the development process. They
are the customers of the final system, owners of the policies and are conveniently co-located with the development team
during the project.
· Responding to change over following a plan. Business rules evolve, more
often and faster than other standard pieces of software. This is actually one of the key values of the business rule
approach. For this fundamental reason the methodology to support the rule set development has to be tailored to such
rapid life cycle and include the appropriate activities, processes, best practices and work products to support such
changes efficiently.
Two fundamental drivers govern successful rule set developments:
· The unforgiving honesty of executable rules
· The effectiveness of people working together with goodwill, shared vision and
common interests (the business user and the development team).
Executable or working rules tell the developers and the Subject Matter Expert what they really do as opposed to promise
through a paper-based design or specification.
ABRD
is a practice and extends other element of EPF practice library to avoid redefining some standard roles, tasks, work
products, guidelines and processes which are also relevant to rule development. As an EPF plug-in, development teams can
leverage it for their own purpose and tailor it to the specific context of their own project, leveraging the EPF Composer
tool.
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