The Communication Manager provides a portable network API. While some applications may use the Communication Manager directly, most applications will use the higher-level Session Manager instead. The Communication Manager produces a transport-oriented view of the network and allows applications to send and receive opaque data. With the Communications Manager, applications have to implement their own protocols on top of this data to allow different machine architectures to share data.

The Datatag Manager allows the developer to create and manipulate application data descriptions called datatags. Datatags are objects that describe the structure and contents of a piece of application data. Datatags allow application data to be easily converted to different representations, and provide a portable description of data structures and contents that allow applications to share data with other applications. The Datatag Manager is used as a bridge between the Representation Manager and the native data representation, expressed in C or C++. A critical issue in building distributed applications is providing support for applications to interact with little or no specific knowledge of the internals of the application data or the services being used. The Datatag Manager and Signature Manager provide APIs that address this issue by providing object-oriented abstractions for data typing, uniform data representation, and service descriptions, to enable transparent interaction between applications across platforms and networks.

The Session Manager includes high-level abstractions that service consumers and service providers use to communicate with each other without explicit knowledge of the network. A session involves two applications communicating with each other, each through its private interface to the session, using the vsession abstraction. A session provides the framework and the link between the service consumer and the service provider. The Session Manager includes the Session Statement Manager, which is used to abstract and encapsulate requests between applications into Statements. Statements are inherently asynchronous, so that service requests can be made and the requesting application can continue running while the request is being handled. Unlike the Communication Manager, users of the Session Manager do not implement protocols, instead acting as service consumers of Communication Manager services.

The Service Manager is used to define service providers—those parts of applications that export services for use by service consumers. A Galaxy application can be a service provider, a service consumer, or both. A Galaxy service is a collection of primitives and attributes. The primitives are the API entry points into the service, which are abstracted through use of the Service Primitive Manager, a manager within the Service Manager. Service consumers use these entry points to make requests of a service. The Service Manager uses the Session Manager for communication between a provider and a consumer.

The Service Broker Manager is used as a high-level interface to the Service Broker from an application. It provides a set of entry points that can be used by service providers to register their services with the Service Broker, and by service consumers to query the Service Broker for available services. The Service Broker Manager uses the Session Manager to communicate between the application and the Service Broker.

The Signature Manager is used as a bridge between statements and primitives. Signatures are primarily used to specify the prototypes for primitives. The statements use these prototypes to help form the actual parameter list to invoke them with, and to identify the return results (if any). The primitives use these prototypes to identify their arguments. Signatures provide a means for type-checking data sent between service consumers and service providers.

The Service Chooser sits on top of the Confirmation Manager and the Service Broker Manager to provide a graphical interface for choosing service providers from those currently available on the network.