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Several conditions exist for keywords and their information. A keyword with accompanying information must always be on one line: no ‘end of line’ LF or CRLF may appear in the information. If the information following the ‘=’ characters consists of several parts, it is separated by commas. The end of the information is specified by the start of a new keyword with a hash (#).

Special characters.

Anchor
Specialcharacters Specialcharacters

A comma (,), equals sign (=) and a hash (#) are therefore special characters. If these characters appear in an information field after a keyword, it must be indicated that the literal meaning of the character is now required. The backslash is used for this purpose: \# \= or \, This also makes the backslash a special character so that if a literal backslash is required in the text, this must also be preceded by a backslash.

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Several conditions must be met if the test is to be meaningful: a minimum description of how the file is organised must be known. This leads to a division of keywords into compulsory, non compulsory and conditionally compulsory keywords. The last category consists of keywords which are in fact compulsory, but for which a default value has been filled in. If the word is therefore not listed, the standard value is used. If the default value is not suitable as a result of another keyword, the word must still be given. It is therefore compulsory under certain conditions. The compulsory keywords are given in Table 2

Compulsory keywords.

Table 2: Compulsory keywordws.

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Table 2 forms the minimum subset of keywords. A file which complies with the geotechnical exchange format uses of all these keywords at least. If one or more of the compulsory keywords are missing then an application should stop automatically processing the data and signal the missing keyword. The test is incomplete. Optionally, the application can query the user so that the missing information can be found. The remaining keywords are given in Table 3.

Non-compulsory keywords.

Table 3: Non compulsory and conditionally compulsory keywords.

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Procedure descriptive keywords state which procedures have been followed, such as how the measuring, sampling, analysing, archiving and reporting activities have been carried out, which additional information was received or was required, and which calculation method was used. Interpretation of the data belonging to these keywords is only possible if the procedure used for the measurement or analysis is known.

[Non]Compulsory and conditionally compulsory

In addition to these categories, a division can also be made into compulsory and non compulsory. The compulsory keywords are given in Table 2. These keywords form the file tracing and file descriptive categories. The compulsory keywords are the minimum requirement concerning the occurrence of keywords with which a GEF file must comply. There are also non compulsory keywords or conditionally compulsory keywords.

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Parts of the information following keywords which can be omitted are given between [] in the typescript. Abbreviations are used to characterise the information, as given in Table 4. E.g. 4Value represents a value of 4 bytes in size, sUnit states a string which describes the unit.

Data types.

Anchor
Datatype Datatype

Table 4: Types of variables and their abbreviations.

Versions.

The set of keywords is not static. Keywords may be added, keywords may become obsolete. Therefore there are versions.  Versions keep track which keywords are allowed. The version of the GEF language which is used in a file, is expressed by its GEFID. By reading the GEFID any functions processing a GEF file, can determine whether the software has sufficient capabilities to process this file. Currently there are three legitimate versions of a GEF file:

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