3. Architectural and Implementation Issues

The remainder of this document provides the technical specifications for the Windows Open Services Architecture (WOSA) Extensions for Financial Services (referred to hereafter as “WOSA/XFS” for brevity).

In this specification, the functions of the WOSA/XFS Application Programming Interface (API) and Service Provider Interface (SPI) are always described in terms of providing a standardized, portable interface for applications to gain access to service providers. This architecture allows service providers to deliver an open-ended set of capabilities to financial applications based on the Microsoft Windows operating systems, including access to peripheral devices unique to financial institutions. Since the first priority of the BSVC members for WOSA/XFS implementations will be to provide this peripheral device access capability, the examples used relate primarily to device control and physical input/output.

The key elements of the Extensions for Financial Services are the API definition and the corresponding SPI definition, used by the XFS Manager to communicate with the service providers, together with the set of supporting services provided by the XFS Manager. These elements are combined in a WOSA/XFS implementation, providing access to financial devices and services for Windows-based applications.

The specification defines a standard set of interfaces in order to provide multi-vendor interoperability: if an application uses the API to communicate successfully with a service provider, it should work with another conformant service provider of the same type, developed by another vendor, without any changes. Similarly, any service provider that conforms to the SPI definition can work with a range of conformant applications.

The specification is intended to be usable within all implementations and versions of the Windows operating systems, beginning with versions 3.1 of Windows, Windows for Workgroups, and Windows NT, and all future versions of these operating systems. In the 16 bit operating systems (Windows 3.x, Windows for Workgroups 3.x) the elements of an XFS subsystem (applications, XFS Manager, and service providers) will be 32 bit modules, implemented using the Win32s API. The specification thus provides for the development and deployment of 32 bit applications on both 16 and 32 bit operating systems, and the WOSA/XFS software development kit will include versions of the XFS Manager and associated programming aids that will allow development of applications and service providers for both environments.

For clarity, three prefixes are used in naming the function interfaces in WOSA/XFS: