12.2. Metadata classes

Metadata it is objects what describe other object and so objects needdes to control of ODB kernel.

Any metadata have obligatory attribute <ID>. This attribute use for access to keeping objects. <ID> created ODB kernel when object append to dictionary.

The metadata counts and names are limited and determine by ODB kernel. The dictionary have object only classes:

DEPOSIT EXTENT ATTR COUNTER INDEX CLASS TCOLUMN TVIEW REPORT PLUGINS USER GROUP

In the dictionary mast be at least one object of each metaclass.

	oDict := coDictionary():new("MY001")
	oDict:open()
	....
	depBody := map()
	depBody:name := "depository for Russian global information"
	...
	dep_id := oDict:append(depBody,"DEPOSIT")
	if !empty(oDict:error)
	   ? "Error:",oDict:error
	endif
	

		extBody := map()
		extBody:name := "statedep"
		extBody:help := "information from state department of statistic"
		...
		ext_id := oDict:append(extBody,"EXTENT")
		....
	

	attr:=map()
	attr:name := "code"
	attr:type := "C"
	attr:len  := 7
	attr:lentype := 3
	....
	code_id := oDict:append(attr,"ATTR")
	....
	attr:=map()
	attr:name := "name"
	attr:type := "C"
	attr:len  := 20
	attr:lentype := 2
	....
	name_id := oDict:append(attr,"ATTR")
	

	indBody := map()
	indBody:name := "code"
	indBody:expr := "code"
	ind1_id := oDict:append(indBody,"INDEX")
	....
	indBody := map()
	indBody:name := "name"
	indBody:expr := "name"
	ind2_id := oDict:append(indBody,"INDEX")
	....
	

	classBody:=map()
	/* information about coding world currencies */
	classBody:name := "currency"
	/* from state department of statistic */
	classBody:extent_id := ext_id
	/* return via "USD:USA dollar" */
	classBody:expr_essence := "code+':'+name"
	/* two attributes "code" and "name" */
	classBody:attr_list := {code_id,name_id}
	/* two index "code" and "name" */
	classBody:idx_list := {ind1_id,ind2_id}

	currency_id := oDict:append(classBody,"CLASS")
	if !empty(oDict:error)
	   ? "Error:",oDict:error
	endif