PrF UG slots override slot - Revision history

RichMorin at 01:49, November 14, 2008

2008-11-14T01:49:18Z

RichMorin: /* Overriding a Slot */

2008-10-29T20:02:02Z

‎Overriding a Slot

RichMorin: /* Overriding a Slot */

2008-10-29T20:01:34Z

‎Overriding a Slot

RichMorin at 21:37, October 25, 2008

2008-10-25T21:37:53Z

RichMorin at 23:08, October 16, 2008

2008-10-16T23:08:46Z

RichMorin at 23:05, October 16, 2008

2008-10-16T23:05:33Z

RichMorin at 23:42, October 14, 2008

2008-10-14T23:42:38Z

RichMorin at 23:41, October 14, 2008

2008-10-14T23:41:53Z

RichMorin at 23:40, October 14, 2008

2008-10-14T23:40:13Z

RichMorin: Automated import of articles

2008-10-09T09:13:02Z

Automated import of articles

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__NOTOC__
== Overriding Slot Properties at a Class ==

{{PrF_UG_TOC_slots}}<div id='prf_ug'>

You can override slot properties by editing the slot at the class level.
This allows you to be more restrictive about the slot facets relative to that class.
A slot with overrides is shown with an override
<div>[[Image:PrF_UG_slots_slot.overridden.gif|slots_slot.overridden]]</div>
icon in the
[[PrF_UG_classes_template_slot_pane|Template Slots pane]].

You can also edit the properties of a slot directly,
instead of just overriding them at a class.
See
[[PrF_UG_slots_edit_top_level|Editing a Top-level Slot]]
for more information.

This topic covers:

<ul class='a'>
<li>
[[#Overriding_a_Slot|overriding a slot]]


<li>
[[#Scope|scope of overrides]]


<li>
[[#Examples|examples]]


<li>
[[#Restrictions|restrictions]]

</ul>

=== Overriding a Slot ===

To edit the slot properties for a specific class:

<ol class='a'>
<li>
Select a class in the
[[PrF_UG_classes_class_window|Class Browser]]
in the
[[PrF_UG_classes_classes_tab|Classes tab]].


<li>
Select the slot you wish to edit in the
[[PrF_UG_classes_template_slot_pane|Template Slots pane]].


<li>
Open the
[[PrF_UG_slots_slot_editor|Slot Editor]]
in one of the following ways:


<ul>
<li>
Click the View Slot Overrides
[[Image:PrF_UG_slots_slot.view_overrides.gif|slots_slot.view_overrides]]
[[PrF_UG_classes_template_slot_buttons|Slot button]]
at the upper right of the
[[PrF_UG_classes_template_slot_pane|Template Slots pane]].


<li>
or Double-click the slot and select View slot at class in the Select Slot View dialog box,
then click OK.
 <div>[[Image:PrF_UG_slots_slot_at_class.png|slots_slot_at_class]]</div>

</ul>

<li>
Change the desired properties in the
[[PrF_UG_slots_slot_editor|Slot Editor]].
See
[[PrF_UG_slots_editing_slot_properties|Editing Slot Properties]]
for more information.

</ol>

After you have edited a slot at the class level,
the slot will be displayed with an override
<div>[[Image:PrF_UG_slots_slot.overridden.gif|slots_slot.overridden]]</div>
icon.

=== Scope ===

Overrides appear:

<ul class='a'>
<li>
at the selected class


<li>
at all of its subclasses

</ul>

Overrides do not appear:

<ul class='a'>
<li>
at the
[[PrF_UG_slots_slots_tab|Slots Tab]]


<li>
at any superclasses


<li>
at any unrelated classes

</ul>

=== Examples ===

<ol class='a'>
<li>
The slot employee_list is a slot of type Instance that takes the value Employee at the top level.
By default,
whenever you attach this slot to a class,
it will range over the instances of Employee.
Suppose,
however,
that for this class,
you want to restrict the possible employees to salespeople.
By overriding the slot,
you can restrict the value range to the Salesperson subclass of Employee for the current class and its subclasses,
without affecting the slot value range for any other class.


<li>
Suppose you had a class of articles which appeared only on work days,
not Saturday or Sunday.
You could override the slot weekday at that class to remove Saturday and Sunday from the Symbol list for that class only,
restricting the possibilities to working days.
Once again,
the top-level slot and its range at other classes will remain unchanged.

</ol>

=== Restrictions ===

When you override a slot at a class,
you can edit slot facets in the same way as you can at the top level.
The override will not remove any existing restrictions,
however,
and may in fact tighten one or more of them:

<ul class='a'>
<li>
The Name of an inherited slot cannot be changed.


<li>
For Cardinality,
the slot may be changed from Multiple to Single,
but not vice versa.
The at least value may be increased;
the at most value may be decreased.


<li>
For certain value types,
some restrictions apply:


<ul>
<li>
For a slot of type Any,
the slot may be restricted to one of the other types (Boolean,
Class,
Float,
Instance,
Integer,
String,
or Symbol).
You cannot change the type of slots other than type Any.


<li>
For a slot of type Class,
the allowed superclasses can only be changed to subclasses of the allowed superclasses in the superclass.


<li>
For a slot of type Instance,
the allowed classes can only be changed to subclasses of the allowed classes in the superclass.

</ul>

<li>
A Minimum value (on types Integer or Float) may be created or increased.


<li>
A Maximum value (on types Integer or Float) may be created or decreased.


<li>
Default values cannot be removed.

</ul>

Note: Currently,
when you override a slot, {{#var:PrF}} does not enforce the restrictive property.
That is,
you could theoretically expand or change the facets of a slot,
rather than restricting them.
However,
it is not recommended that you do this,
both because it is not good practice and because {{#var:PrF}} may enforce restriction in the future.

</div>

@@ Line 2: / Line 2: @@
 == Overriding Slot Properties at a Class ==
-{{PrF_UG_TOC_slots}}<div id='prf_ug'>
+<noinclude>{{PrF_UG_TOC_slots}}<div id='prf_ug'></noinclude>
 You can override slot properties by editing the slot at the class level.
@@ Line 193: / Line 193: @@
-</div>
+<noinclude></div></noinclude>

@@ Line 46: / Line 46: @@
      <li><p>
-       <i>or</i> Double-click the slot and select <b>View slot at class</b>
+       Double-click the slot and select <b>View slot at class</b>
        in the <b>Select Slot View</b> dialog box,
        then click <b>OK</b>.

@@ Line 64: / Line 64: @@
 After you have edited a slot at the class level,
 the slot will be displayed with an override
-[[Image:PrF_UG_slots_slot.overridden.gif|slots_slot.overridden]] icon.
+([[Image:PrF_UG_slots_slot.overridden.gif|slots_slot.overridden]]) icon.
 === Scope ===

@@ Line 7: / Line 7: @@
 This allows you to be more restrictive about the slot facets relative to that class.
 A slot with overrides is shown with an override
-[[Image:PrF_UG_slots_slot.overridden.gif|slots_slot.overridden]] icon
+([[Image:PrF_UG_slots_slot.overridden.gif|slots_slot.overridden]]) icon
 in the [[PrF_UG_classes_template_slot_pane|Template Slots pane]].
@@ Line 22: / Line 22: @@
    <li><p>
      Select a class
-     in the [[PrF_UG_classes_class_window|Class Browser]]
+     in the [[PrF_UG_classes_classes_tab|Classes tab]]
-     in the [[PrF_UG_classes_classes_tab|Classes tab]].
+     of the [[PrF_UG_classes_class_window|Class Browser]].
      </p>
@@ Line 39: / Line 39: @@
      <li><p>
        Click the <b>View Slot Overrides</b>
-       [[Image:PrF_UG_slots_slot.view_overrides.gif|slots_slot.view_overrides]]
+       ([[Image:PrF_UG_slots_slot.view_overrides.gif|slots_slot.view_overrides]])
        [[PrF_UG_classes_template_slot_buttons|Slot button]]
        at the upper right
@@ Line 50: / Line 50: @@
        then click <b>OK</b>.
        </p>
-       <div>[[Image:PrF_UG_slots_slot_at_class.png|slots_slot_at_class]]</div>
+       <div>[[Image:PrF_UG_slots_slot_at_class.png|frame|none|
    </ul>
@@ Line 83: / Line 84: @@
 <ul class='a'>
    <li><p>
-     at the [[PrF_UG_slots_slots_tab|Slots Tab]]
+     at the [[PrF_UG_slots_slots_tab|Slots tab]]
      </p>
@@ Line 190: / Line 191: @@
 both because it is not good practice
 and because {{#var:PrF}} may enforce restriction in the future.
 </div>

@@ Line 83: / Line 83: @@
 <ul class='a'>
    <li><p>
-     at the
+     at the [[PrF_UG_slots_slots_tab|Slots Tab]]
      </p>
@@ Line 100: / Line 99: @@
 <ol class='a'>
    <li><p>
-     The slot <b>employee_list</b> is a slot of type <b>Instance</b> that takes the value <b>Employee</b> at the top level.
+     The slot <b>employee_list</b> is a slot of type <b>Instance</b>
-     By default,
+    that takes the value <b>Employee</b> at the top level.
-    whenever you attach this slot to a class,
+     By default, whenever you attach this slot to a class,
      it will range over the instances of <b>Employee</b>.
-     Suppose,
+     Suppose, however, that for this class,
      you want to restrict the possible employees to salespeople.
-     By overriding the slot,
+     By overriding the slot, you can restrict the value range
-    you can restrict the value range to the <b>Salesperson</b> subclass of <b>Employee</b> for the current class and its subclasses,
+    to the <b>Salesperson</b> subclass of <b>Employee</b>
      without affecting the slot value range for any other class.
      </p>
@@ Line 116: / Line 114: @@
      Suppose you had a class of articles which appeared only on work days,
      not Saturday or Sunday.
-     You could override the slot <i>weekday</i> at that class to remove <i>Saturday</i> and <i>Sunday</i> from the <b>Symbol</b> list for that class only,
+     You could override the slot <i>weekday</i> at that class
      restricting the possibilities to working days.
-     Once again,
+     Once again, the top-level slot and its range at other classes will remain unchanged.
      </p>
 </ol>
@@ Line 127: / Line 125: @@
 When you override a slot at a class,
 you can edit slot facets in the same way as you can at the top level.
-The override will not remove any existing restrictions,
+The override will not remove any existing restrictions, however,
 and may in fact tighten one or more of them:
@@ Line 145: / Line 142: @@
    <li><p>
-     For certain value types,
+     For certain value types, some restrictions apply:
      </p>
@@ Line 152: / Line 148: @@
      <li><p>
        For a slot of type <b>Any</b>,
-       the slot may be restricted to <i>one</i> of the other types (<b>Boolean</b>,
+       the slot may be restricted to <i>one</i> of the other types
-      <b>Class</b>,
+      (<b>Boolean</b>, <b>Class</b>, <b>Float</b>, <b>Instance</b>,
-      <b>Float</b>,
+       <b>Integer</b>, <b>String</b>, or <b>Symbol</b>).
        You cannot change the type of slots other than type <b>Any</b>.
        </p>
@@ Line 164: / Line 156: @@
      <li><p>
        For a slot of type <b>Class</b>,
-       the allowed superclasses can only be changed to subclasses of the allowed superclasses in the superclass.
+       the allowed superclasses can only be changed to subclasses
        </p>
      <li><p>
        For a slot of type <b>Instance</b>,
-       the allowed classes can only be changed to subclasses of the allowed classes in the superclass.
+       the allowed classes can only be changed to subclasses
        </p>
    </ul>
    <li><p>
-     A <b>Minimum</b> value (on types <b>Integer</b> or <b>Float</b>) may be created or <i>increased</i>.
+     A <b>Minimum</b> value (on types <b>Integer</b> or <b>Float</b>)
      </p>
    <li><p>
-     A <b>Maximum</b> value (on types <b>Integer</b> or <b>Float</b>) may be created or <i>decreased</i>.
+     A <b>Maximum</b> value (on types <b>Integer</b> or <b>Float</b>)
      </p>
@@ Line 186: / Line 182: @@
 </ul>
-<b>Note:</b> Currently,
+<b>Note:</b>
-when you override a slot, {{#var:PrF}} does not enforce the restrictive property.
+Currently, when you override a slot,
-That is,
+{{#var:PrF}} does not enforce the restrictive property.
-you could theoretically expand or change the facets of a slot,
+That is, you could theoretically expand or change the facets of a slot,
 rather than restricting them.
-However,
+However, it is <i>not</i> recommended that you do this,
-it is <i>not</i> recommended that you do this,
+both because it is not good practice
-both because it is not good practice and because {{#var:PrF}} may enforce restriction in the future.
+and because {{#var:PrF}} may enforce restriction in the future.
 </div>

@@ Line 54: / Line 54: @@
    <li><p>
-     Change the desired properties in the
+     Change the desired properties
-    [[PrF_UG_slots_slot_editor|Slot Editor]].
+    in the [[PrF_UG_slots_slot_editor|Slot Editor]].
-     See
+     See [[PrF_UG_slots_editing_slot_properties|Editing Slot Properties]]
      for more information.
      </p>