Rulebase technology for GIS applications
Object maintenance using a rulebase
Despite improvements in analysis and object modeling, a large body of existing
knowledge about facilities data models, and the great overlap in business practices among
utilities, it is the sad fact that data models must be maintained. Over the life cycle of an
AM/FM/GIS, requirements and business practices can change, resulting in the need to
add or modify properties and methods of objects, and even to add new objects to the
model. Though the benefits of creating an AM/FM/GIS using a RuleBase are great, the
benefits of maintaining it through this technique are even greater.
The first benefit for object maintenance using the RuleBase comes from the fact that the
model can be easily updated using the standard CASE tools or manual techniques
described in the preceding section. As an example, the order in which a valve 'looks for'
other objects such as mains and laterals to which it can connect itself can be simply
described in row-and-column form in a RuleBase. If a new object is added to the model
to which a valve can connect, the RuleBase can be updated simply by adding another
row. Because low-level coding is minimized or eliminated altogether, the RuleBase can
be simply updated, and the engine used to re-instate the object with its new properties and
methods.
This ability has two indirect benefits that are worth noting. First, using a modern
architecture in the applications context, the RuleBase can be maintained with minimal
impact on users. It is possible, for example, to load the RuleBase of objects into memory
along with an application, enabling any user to continue to work while the production
RuleBase is undergoing maintenance. When the modified RuleBase is ready for release,
each user can simply exit the application and start again, reloading the RuleBase with
modifications. This is also a significant benefit where large volumes of production data
exist, enabling all objects to be re-structured with minimal impact. (Of course, any new
properties of existing objects will have to be populated somehow, but the RuleBase can
also be handy for populating default values of existing objects.)
One more side benefit of using a RuleBase technique to create a functioning data model:
the RuleBase itself is a convenient and comprehensive documentation tool. Because the
RuleBase stores the relations, validations, and connectivity/cartography, it is a good place
to refer to all object metadata. Further, consistency between the RuleBase and the actual
object structures in production is a key function required for model maintenance. Most
commercially available RuleBase tools have consistency checking and reporting tools.
One rulebase, many applications
The modern AM/FM/GIS may no longer be thought of as a map and database
maintenance tool. Today's requirements dictate that the AM/FM/GIS database be
available to create a variety of geographic and non-geographic applications used by an
even greater variety of personnel.
By abstracting business rules and properties of the objects that represent the real-world
facilities and storing those in the RuleBase, the model can be used by many applications,
both spatial and non-spatial. This approach helps to simplify the implementation of many
lighter-weight applications, removing the onus of having the application (or the user)
know the data structures and relationships to be used in composing a query or a display.
Even casual users can gain access to detailed data through relations, and data displayed
by different applications appears consistently to all users. Most importantly, the
RuleBase can be used to help ensure that editing operations (either geographic or tabular)
follow a consistent set of methods or rules, including validations, to secure data and to
maintain its integrity.
