Basics

Description files are text files which can be created and modified with an editor. They have the following properties:

• they are free format; there is no requirement that items occur at fixed absolute positions in lines,

• the space character is used as a separator; items in the description must be separated by one or more spaces,

• keywords are case-insensitive (though throughout this manual they are shown in upper-case for clarity),

• blank lines are ignored; they may be introduced freely to improve readability as required.

A CURSA catalogue comprises: columns, parameters and textual information (see Section ). All these items are defined in the description file. It can also contain directives which provide additional information. Each column, parameter, line of textual information and set of directives occupies one or more contiguous lines of the description file. The components can occur in any order.

The first non-blank character of a line determines the type of component it contains, according to the following scheme:

C	-	column,
P	-	parameter,
T	-	textual information,
D	-	directive,
:	-	continuation of the preceding line.

These characters do not have to occur at the start of a line; they can be preceded by (and only by) an arbitrary number of spaces. The single character is all that is required to specify the type of component. However, it can be part of a word if required for clarity, as long as the word starts with the correct letter. For example, `COLUMN' could be used instead of `C' to introduce a column.

Columns and parameters have the following general format:

C or P    mandatory items    optional items

All items must be separated by one or more spaces. The mandatory items must be supplied. They occur in a fixed order and only the value is given. The optional items usually correspond to attributes of the column or parameter. They may be supplied if required; if they are omitted defaults are adopted. Optional items are specified using the notation:

item_name=value

Spaces are not permitted between the item name, equals sign and value. The mandatory and optional items for columns and parameters are described in Sections  and respectively.

Textual information has the following format:

T    line of text

Note that there must be one or more spaces between the `T' (or word beginning with `T') and the line of textual information. CURSA accesses lines of textual information in the order in which they are entered into the description file.

Sets of directives have the format:

D    directives

An arbitrary number of directives can be specified on each line. Each directive is specified using the notation:

directive_name=value

Spaces are not permitted between the directive name, equals sign and value. The various directives are listed in Section .