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3.1 Purpose

The purpose of this specification is to define embedded system application programming environments (or profiles) based on the Linux operating system. This is intended for embedded system implementers and embedded application software developers. Embedded systems are systems either constrained or purposely optimized for a given environment.

This specification is built upon a much larger and widely supported set of standards, in particular:

• The Linux Standards Base 1.2
  
• The IEEE POSIX 1003.1-2001 specification, which supersedes the 1996 version and contains updates for Realtime, Threads and Networking.
  
• The Single UNIX Specification v3, which supersedes the UNIX98 standard and was produced in conjunction with IEEE POSIX 1003.1-2001.

These allow for the formation of a specification with a sound footing in industry-standard behavior. At the same time, this document is designed to allow for extension and future enhancement as the industry progresses.

This standard defines three environments to reflect the wide range of system requirements presented by embedded designs. The intent is to provide meaningful and coherent sets of interfaces that will present software vendors and consumers with a uniform framework for describing and specifying system capabilities. This allows an application writer to construct an application that may be easily moved to a different system that supports the same environment. Similarly, it allows a vendor to claim conformance with an established specification.

This specification is designed to support the common practice of interconnecting several smaller systems to create larger systems. Each interconnected system may use different ELCPS (or other) environments. For example, one can envision a hierarchical system where the bottom- level elements (e.g., device controllers) use the "minimal" environment, the next level up uses the somewhat larger "intermediate" environment, and so on. For this reason the Platform Specification specifies interfaces for the smaller environments that make no sense for an isolated system. These interfaces are specified to support the construction of hierarchical systems as well as systems of communicating heterogeneous peers.

In summary, the ELCPS aims:

• To promote development of embedded Linux systems and applications,
  
• To allow for scalability in those environments, based on intended uses,
  
• To promote portability of embedded Linux applications,

and it will do this by

• Using existing Linux and UNIX industry standards
  
• Allowing for adaptation to existing Linux common practice
  
• Breaking down the environments into recognized sets of function, for configurability.

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