Introduction to Part 5

Organisation

Part 5, Application Portability describes application portability in the SPIRIT environment.

It is structured as follows:

• Introduction (this chapter).

• Source Code Transfer Profiles (see Source Code Transfer Profile ).

  Describes the model, portable media, telecommunications protocols, interchange formats, character sets and code sets in the SPIRIT environment.

• Source Code Portability Profiles (see Source Code Portability Profiles ).

  Describes the SPIRIT language profiles, the SPIRIT inter-language calls profile, and support of data types in the SPIRIT environment.

Purpose

As noted in Part 1, Overview and Core Specifications, the aim of SPIRIT is to produce an agreed set of specifications for a general-purpose computing platform that ensures both application portability and interoperability.

Part 5, Application Portability defines those elements of a development environment necessary to ensure application portability.

This part summarises the concepts of application portability and the development environment specifications required to ensure application portability.

Requirements

Application portability is defined as the ability to make an application running on one open system run on another, regardless of the supplier, with minimal modification.¹ Although application code can be ported in various forms, SPIRIT's definition of application portability involves porting applications at the source code level. Thus SPIRIT defines application portability as the ability to:

• transfer source code and reference data from one implementation of a SPIRIT-compliant platform to another implementation of a SPIRIT-compliant platform²

• reconstruct an operational application on the target platform with minimal or no modification to the application source code, resulting in a new application instance with behaviour identical to the original.

The first requirement is to provide the mechanisms for source code and reference data transfer. This is addressed by a source code transfer profile.

The second requirement is to preserve the application source code and maintain consistent operational semantics between the source and target platforms. This is addressed by the source code portability profile.

The major benefit gained from application portability is the reduction in the cost of modifying and maintaining applications when:

• re-using common module code on multiple platform implementations

• porting applications to multiple platform implementations

• replacing one platform implementation with another.

Additional benefits from application portability include:

• reduced training costs for application programmers, due to using similar interfaces

• improvement in application development productivity and quality

• obtaining maximum leverage on the investment in hardware and software for development work groups.

Footnotes

1.

This definition is derived from X/Open XPG4.

2.

SPIRIT implementations may be distinguished by different combinations of software component implementations as well as different hardware architectures.