5. Language Programming Interfaces

1. 5.1. The DRA C LPI
2. 5.2. The DRA C++ LPI
3. 5.3. The Etnoteam Fortran LPI

A Language Programming Interface (LPI) is here defined to mean a set of tokens, usually specific to a particular producer, which will encapsulate language features at a higher level than basic TDF constructs, more convenient for the producer to produce.

Responsibility for the specification of individual LPIs lies with the appropriate producer itself. Before an application can be installed on some target platform, the appropriate LPI token definitions must have been built for that platform. In this sense, the LPI can be considered as a primitive API, which is discussed in §6.

The process by which the LPI token definition library or capsule is generated for any specific platform will vary according to the LPI, and responsibility for defining that process will also lie with the appropriate producer. Some LPIs, such as that associated with DRA's C producer, can be fully defined by architecture neutral TDF, using the tokens specified in §2 and §3 to encapsulate any target dependencies. When that is the case, the generation process can be fully automated. For other LPIs the process may be much less automated. In some cases where the source language implies a complex run-time system, this might even require a small amount of new code to be written for each platform.

Generally, the individual LPI tokens do not need to be specified in the token registry, provided they follow a registered naming scheme to ensure uniqueness (see §1). In exceptional circumstances it may be necessary for some TDF tool to recognise individual LPI tokens explicitly by name. This will be the case when experimenting with potential extensions to TDF, in the field of parallelism for example. In other cases a TDF installer or other tool may recognise an LPI token by name rather than its definition by choice, for some unspecified advantage. We make a pragmatic choice in such cases whether to include such token specifications in the token registry. For widely used producers, we can assume availability of the LPI token specifcations, or standard definitions, separately from the token register, but we should expect any such tokens to be specified within the register for all cases where significant advantage could be taken by an installer only if it recognises the token by name.