POSIX.8 - Transparent File Access

The purpose of this amendment to POSIX.1 is to extend and circumscribe the file access aspects of the operating system interface to support file access mechanisms which are incapable of supporting the full behavior required by POSIX.1 or which provide access to files via a networked mechanism.

Transparent File Access (TFA) [POS93] is a specification of system services including file behavioral characteristics. With regard to file behavioral characteristics, the TFA Specification describes the behavior that an application can expect when manipulating a file.

The goal of the TFA Working Group is to provide a file use specification that:

1. Permits the use of the widest possible kinds of file systems which can resemble the file system of POSIX.1 so that most implementors and programmers can make use of the specification.

2. Allows an application to determine the behavior which it can expect when manipulating a file. In particular, the specification allows an application to determine when behavior is not in accordance with POSIX.1.

3. Provides the means for an application to simultaneously manipulate files whose access characteristics may differ since they reside in different file systems.

To be able to access systems that do not meet the specifications of POSIX.1, file characteristics of P1003.1 have been grouped into subsets thats allow non-POSIX.1 files to be described. The interfaces that interact with the file characteristics have been modified to accept these subsets of P1003.1 file characteristics. A system compliant with the POSIX.8 specifications must use files that can be described as either Full TFA, Core TFA, or Subset TFA.

Full TFA requires the specifications of POSIX.1.

Core TFA is the minimum set of characteristics that must be provided so that a file is usable according to the TFA Specifications. Core TFA:

1. Must support regular files.

2. Need not support execute/search permission bits.

3. Need not support file owner or file group class.

4. May result in files being created or modified as a result of a failed open().

Subset TFA refers to a set of file behavioral characteristics that at least conforms to Core TFA but does not conform to Full TFA. For a more complete discussion of Transparent File Access, see [OB91].