The DC GIS web services are attractive to many developers and their customers for a number of reasons including cost savings:
Services are available in a time and location independent manner (controlled primarily by DC GIS).
Embed GIS functionality without paying for it.
Providing access to extremely large datasets for both high and low bandwidths.
The most current DC GIS data is readily available. Data updates do not require local maintenance.
Differences in native formats and coordinate systems are less of a barrier to use.
Used in a broad range of situations, from complex projects or applications to one-off uses.
DC GIS web services are most useful when:
the user needs the most current data; (e.g., MAR addressing database is updated/edited in real-time).
the data is subject to frequent change.
the user just needs the data for background use (e.g., our basemap as a backdrop for a map view).
the data is not readily available or cannot be efficently acquired, maintained and stored for local use (e.g., agency would like to use DC GIS addressing database but does not have the staff or technical resources to host and maintain the data-set).
Others reasons include:
the need to add a map to an existing web page or application. Developers can tuck a map into an existing web page. It is a map with no zooming/panning tools, but a map generated fresh from the database each time the user loads the page. Or it can have panning/zooming controls. The page is minimally altered and the application can be written in any programming language - as long as it can send and receive XML it can talk to the DCGIS Web Mapping Services.
the need to create maps using sensitive data without sharing the data.
the application has a function to accept user entered DC addresses and the need for validation is necessary. If so, retrieve the coordinates for that address so that you can map it.