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This file documents the Grand OAF Database Query Language.
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Strings: As in SQL, delimited by single quotes. Example: 'mystring'
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Stringvs (string arrays): A comma-separated list of strings, surrounded by square brackets. Example: ['red','blue']
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Numbers: Floating point decimals. (aka "whatever atof() accepts" :)
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Booleans: TRUE or FALSE (other common boolean value identifiers also accepted, but not encouraged).
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Names of fields are attributes of a ServerInfo record. These include
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'type', 'location_info', and 'iid', even though these are explicitly
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stored instead of just other attributes.
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Some pseudo-fields are also available - they are all prefaced with an underscore:
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_active - Whether the server is currently running (boolean)
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Variables are various miscellaneous data items that are part of the
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environment. The syntax for referring to a variable is a '$' sign
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followed by the variable name. The following variables are available:
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$hostname - the hostname that the requesting client is running on.
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$domain - the "domain" that the client is requesting activation in.
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Functions perform transformations on data and return a result. There are two possible syntaxes for a function call:
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field.funcname(other-arguments...)
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Internally, 'field.funcname(other-arguments...)' is translated to be
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exactly the same as 'funcname(field, other-arguments)', so
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'priority.max()' is exactly the same as 'max(priority)'. The following functions are available:
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Returns a boolean value that indicates whether the given expression is defined for the current
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record. For example, using a field name would indicate whether that field is defined for the
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has_one(stringv1, stringv2)
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Returns a boolean value that indicates whether any of the strings
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in the 'stringv2' array are contained in the 'stringv1' array.
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has_all(stringv1, stringv2)
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Returns a boolean value that indicates whether all of the strings
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in the 'stringv2' array are contained in the 'stringv1' array.
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Returns a boolean value that indicates whether 'string' is contained in the 'stringv' array.
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prefer_by_list_order(string, stringv)
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This function is intended to use as a sort condition when you have a prioritized list of
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preferred values. It returns -1 if the 'string' is not in the 'stringv' array, otherwise
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it's position measured from the end of 'stringv'. The result is that the first item is
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most preferred, items after that are next most preferred, and items not in the list are
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Evaluates 'expr' over all the available server information records in the database, and returns
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the maximum value as dictated by the normal sort order for the data type of 'expr'.
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This function is not valid for string vectors.
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As with the 'max' function, but finds the minimum value.
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Function names are case insensitive.
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Binary relational operators
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>= greater than or equal
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Binary boolean operators
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Unary boolean operators
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Binary arithmetic operators
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Unary arithmetic operators
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To get a component implementing the IDL:GNOME/Graph/Layout interface you might use:
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CORBA_Object o = oaf_activate ("repo_ids.has ('IDL:GNOME/Graph/Layout:1.0')",
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A more complicated query might be:
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"(repo_ids.has_all (['IDL:Bonobo/Control:1.0',
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'IDL:Nautilus/ContentView:1.0']) OR
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repo_ids.has_one (['IDL:Bonobo/Control:1.0',
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'IDL:Bonobo/Embeddable:1.0'])) AND
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repo_ids.has('IDL:Bonobo/PersistFile:1.0') AND
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This would get any component with both 'Control' and 'ContentView' or
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with either 'Control' or 'Embeddable' as long as they supported the
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'PersistFile' interface, and defined the attribute 'foo:bar'.
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doc/activation/query-language.txt
