Roles (query directive) - Revision history

Olli: /* Examples */

2009-08-20T09:47:22Z

‎Examples

Olli at 09:47, 20 August 2009

2009-08-20T09:47:10Z

Olli at 07:44, 20 August 2009

2009-08-20T07:44:57Z

Olli at 07:42, 20 August 2009

2009-08-20T07:42:48Z

New page

== Description ==

Returns the input row but with only the specified roles. If a role is not found in input, it is added with null value.

== Constructor ==

Roles(String s1,...)

@@ Line 13: / Line 13: @@
 ''Roles'' is typically used to remove columns that are needed inside the query but not necessarily wanted for the final result. For example, following query finds which instance of the input are also subclasses of it. Without the ''Roles'' directive it would have three columns "#instances", XTMPSI.SUPERCLASS and the default column which is the initial input topic. "#instances" and XTMPSI.SUPERCLASS are always the same topic because we're only looking for rows where this is the case. But we don't need to see this same topic twice. Also we don't usually really need to see the input topic either. So we can use ''Roles'' directive to remove everything else but "#instance" which contains all we need to see.
-importPackage(org.wandora.query2);
+ importPackage(org.wandora.query2);
-importPackage(org.wandora.topicmap);
+ importPackage(org.wandora.topicmap);
-new Roles("#instance").from(
+ new Roles("#instance").from(
-  new Join(
+   new Join(
-    new Instances().as("#instance"),
+     new Instances().as("#instance"),
-    new Players(
+     new Players(
-      XTMPSI.SUPERCLASS_SUBCLASS,
+       XTMPSI.SUPERCLASS_SUBCLASS,
-      XTMPSI.SUBCLASS).whereInputIs(XTMPSI.SUPERCLASS)
+       XTMPSI.SUBCLASS).whereInputIs(XTMPSI.SUPERCLASS)
-  ).where("#instance","t=",XTMPSI.SUBCLASS)
+   ).where("#instance","t=",XTMPSI.SUBCLASS)
-−
+ )

← Older revision		Revision as of 09:47, 20 August 2009
Line 8:		Line 8:

	[[Category:Query directives]]		[[Category:Query directives]]
		+
		+	== Examples ==
		+
		+	''Roles'' is typically used to remove columns that are needed inside the query but not necessarily wanted for the final result. For example, following query finds which instance of the input are also subclasses of it. Without the ''Roles'' directive it would have three columns "#instances", XTMPSI.SUPERCLASS and the default column which is the initial input topic. "#instances" and XTMPSI.SUPERCLASS are always the same topic because we're only looking for rows where this is the case. But we don't need to see this same topic twice. Also we don't usually really need to see the input topic either. So we can use ''Roles'' directive to remove everything else but "#instance" which contains all we need to see.
		+
		+	importPackage(org.wandora.query2);
		+	importPackage(org.wandora.topicmap);
		+	new Roles("#instance").from(
		+	new Join(
		+	new Instances().as("#instance"),
		+	new Players(
		+	XTMPSI.SUPERCLASS_SUBCLASS,
		+	XTMPSI.SUBCLASS).whereInputIs(XTMPSI.SUPERCLASS)
		+	).where("#instance","t=",XTMPSI.SUBCLASS)
		+	)

← Older revision		Revision as of 07:44, 20 August 2009
Line 6:		Line 6:

	Roles(String s1,...)		Roles(String s1,...)
		+
		+	[[Category:Query directives]]