16. A method as defined in claim 15 in which data is imported into said file by: verifying that said data is of an allowed kind and that it has a permitted link hierarchy; creating a set of ordered intermediate tables with headings corresponding to queries on the external data base; combining said tables into a single table in which each of the column headings is prefixed to its column values to create data sets, each having a data type defined by the column value; and reformatting said table as a data set array.
16. A method as defined in claim 15 in which data is imported into said file by: verifying that said data is of an allowed kind and that it has a permitted link hierarchy; creating a set of ordered intermediate tables with headings corresponding to queries on the external data base; combining said tables into a single table in which each of the column headings is prefixed to its column values to create data sets, each having a data type defined by the column value; and reformatting said table as a data set array. 18. A method as defined in claim 16 in which the combined table is reformatted into a data set array by: reading each row in said table and each data set in that row; prefixing at least one hierarchy designator corresponding to the level of the data set in a row to each said data set; inserting end-of-data-set delimiters at the end of each said data set; and adding the thus delimited data sets in order to a user defined key data set to create a data set array as aforesaid.