Keywords

The entry for an individual database in a configuration file comprises some of the following keywords. The entry for the database must begin with the serv_type keyword. Other keywords can occur in any order. The keywords are optional unless otherwise indicated. The keywords are case-sensitive and must be specified entirely in lower case.

serv_type

(mandatory) The type of database. The options permitted are described in Section , below.

long_name

(mandatory) A one-line description of the database. Typically the client will display it to allow the user to identify the database.

short_name

(mandatory) A short name for the database. Conventionally it has the form:

database@institution

where database is an abbreviation for the database and institution a standardised abbreviation for the institution where the on-line version is located. By convention institution has three or four characters; some common values are listed in Table .

Table: Abbreviations for institutions hosting ACL servers

Abbreviation	Institution
cadc	Canadian Astronomy Data Centre, Dominion Astrophysical Observatory
eso	European Southern Observatory, Garching bei München
lei	Department of Physics and Astronomy, University of Leicester
roe	Royal Observatory Edinburgh

url

(mandatory) The URL and query template to access the server. See Section .

symbol

Defines how objects in the returned table should be plotted. See Section .

copyright

A copyright notice for the client to display.

search_cols

A list of columns on which range searches are permitted. See Section .

sort_cols

The columns on which the returned table is sorted.

sort_order

The order into which the returned table is sorted. The permitted values are: increasing and descreasing.

show_cols

By default a client will display all the columns in the returned table. If a show_cols list is specified then by default only the columns in the list will be displayed. Also the order of the list defines the order in which the columns should be displayed.

id_col

The number of a column in the returned table which contains a unique identifier (or `name') for each object in the table. By default the first column of a TST format table contains such an identifer (see Section ).

ra_col

The number of a column in the returned table which contains the Right Ascension. By default the second column of a TST format table contains the Right Ascension (see Section ).

dec_col

The number of a column in the returned table which contains the Declination. By default the third column of a TST format table contains Declination (see Section ).

x_col

The number of a column in the returned table which contains $x$ image pixel coordinates.

y_col

The number of a column in the returned table which contains $y$ image pixel coordinates.

is_tcs

If this keyword is present it should be set to `1'. Its presence indicates that the returned table either is in or should be converted to TCS format. TCS format catalogues have fixed column names and rules for converting column names when catalogues are imported from other formats.

help

A URL pointing to a Web page (or pages) describing the database.

backup1

A reserve URL to be used to access the database in the case where the URL specified by the url keyword does not respond.

backup2

A second reserve URL to be used to access the database in the case where the URLs specified by the url and backup1 keywords do not respond.

For keywords id_col, ra_col, dec_col, x_col and y_col the number of a column is defined as its sequence number in the list of column names which defines the columns in a TST table (see Section  and Figure ). The first column is numbered zero. This sequence number is sometimes referred to as the `column index'.