GIS services provided by ESRI products can be utilized by server developers via the appropriate API.  Each type of GIS service defines a different API by which it can be consumed.   This service or data source specific API often provides fine-grained access to service capabilities.  Some products consolidate the use of data source specific APIs to integrate capabilities and results in a single developer environment.  One such example is the Web ADF, which implements data source specific APIs to take advantage of common functionality in a single generic framework.  As a result, the Web ADF includes the API for each data source it supports, which means the data source API is available for use independent of the Web ADF.  For example, the Web ADF install includes the ArcObjects primary interop assemblies and object libraries that are necessary to work with ArcObjects remotely, on the GIS Server.  Developers who have installed the Web ADF can choose to work with the ArcObjects directly (via ArcGIS Server) instead of the Web ADF controls.  The following developer APIs, specific to the type of data source they work with, are available: