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Data Distribution
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Taking your enterprise AM/FM/GIS on the road
- Server Based Querying
At first glance this would appear to be exclusively Intemet and Intranet solutions. But actually, this can use both a
thin or a thick client' architecture. In the previous section on Disk Image Replication, the user transported a
complete copy of the data with them, wherever they may be, either in the office or in the field. With the use of a
server, users can then request information without needing the entire dataset locally.
Typically, this is the second tier of an implementation schedule. After users and administrators alike, become more
familiar with the technology and what it can do for them, people start to become attune to such buzzwords as
"latency" and "data currency." As mentioned earlier, the Disk Image Replication method tends to become unruly
once a large implementation begins. This is where users need and request for data on a larger scale, and with the
data more up to date.
Server Based Querying can, as mentioned come in many different forms. Most likely, the Records or Drafting
Departments maintaining the Spatial Database use this concept themselves. Here, users use the 'Cadillac'of
interfaces to input and revise data, typically using clientserver mechanisms to retrieve and store data from a local
server.
But, desktop users such as Engineers, Designers and Planners can use systems to request data from the server as
well. In these cases, thick clients tend to be the choice. The local interface is based on a subset of the drafting and
maintenance tools used on the design seats. With specific and targeted user interfaces, this class of application is
deemed the main driver of the corporate Spatial Database.
Finally, there are the casual users out in distributed sites or connecting via temporary phone lines that need to query
the system. These users typically need to request specific information as well, such as the location of a particular
switch, valve or the customer's service connection. These users can make use of a variety of thick or thin clients
that can request information from a server and have the required information displayed on their screen
automatically. In some instances specialized decision support software aid them in the correct response to a
situation happening before them in the field.
The distinct advantage of this solution, in relation to the others is that this tends to be the least expensive to
maintain. The initial implementation costs will tend to be more than the more "primitive" Disk Image Replication
methods, which is why most managers will opt for this after the initial roll-out of a project. After the initial phases,
however, this tends to be the more cost effective method, if the applications are intuitive and the users trained
properly in their use.
The age of the data in these implementations is the best available today. Here users are looking directly into the
corporate Spatial Database during their queries. In high risk situations, is where this really shines. Linestaff
climbing poles and connecting services need the latest information, and by using a laptop in the trucks or even in the
garage before leaving for a job, they can be assured that the data displayed is the latest available. In most instances,
the past practices have been monthly circuit plans, printed out in books of 11x 17" paper on a monthly basis. This
can now be replaced with a computer in a boom truck or in a foreman's office in the service garage.
The one drawback to this method, is the reliance on the network. This is adequate, even desirable in the office or
where reliable and fast telephone lines are available, but in other situations, hybrid implementations are optimal.
Table 1: Replication Options available
| Option Description |
Technical complexity |
Data concurrency |
Relative cost to implement |
Cost to maintain |
Application Requirement |
| Disk image replication |
Low |
Low |
Low |
Moderate |
High |
| Server based querying |
Moderate |
High |
Moderate |
Low |
Varies |
| Database replication |
High |
High |
Moderate to high |
Moderate to low |
minimal |
1Thick and Thin clients are a term used to describe the amount of local resources used for an application. The
classic thin client is a Web browser with no addition software, used to view simple text on screen. However, in the
context of a Spatial Thin client, there will be some minor additional software downloaded to the workstation to view
the content. A thick client is typically a stand-alone application that runs in its own memory space and uses its own
interface.
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