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Home : Matrix Language : Pattern Statements : Traverse Identifier Statements |
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Traverse Identifier Statements |
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Statements
TraverseIdentifier TraverseKey NullIdentifierSelection
General
The purpose of the TraverseIdentifier statement is to select a particular object when navigating a relationship using identifying attributes.
The TraverseIdentifier statement is used within the Traverse and TraverseUnique statements.
TraverseIdentifier Statement
StateAction Traverse TraverseIdentifier:Dog:Dog_Name TraverseKey Dog : Name : Dog_name Dog_Owner : Name : Dog_owner_name NullIdentifierSelection | An object of Dog could not be found with the supplied | identifying attributes.
The TraverseIdentifier statement introduces one TraverseKey statement and one optional NullIdentifierSelection statement.
TraverseKey Statement
StateAction Traverse TraverseIdentifier:Dog:Dog_Name TraverseKey Dog : Name : Dog_name Dog_Owner : Name : Dog_owner_name
The TraverseKey statement's data subregion specifies the values to be used for the identifying attributes. The attributes may belong to the searched entity or to a foreign entity. The fields of the data region are: name of the entity, name of the identifying attribute, name of data item containing the value to be matched.
NullIdentifierSelection Statement
StateAction Traverse TraverseIdentifier:Dog_Home:Dog_Home_Name TraverseKey Dog_Home : Name : Dog_home_name NullIdentifierSelection | An object of Dog Home could not be found with the | supplied identifying attribute. Template <<|>>Only the original context of Manager is available <<:>>in this subregion. Thus <<#Manager.Name>> is valid.
The optional NullIdentifierSelection statement provides a subregion where the statements are only executed if during the navigation an object fails to match with identifying values.
If the NullIdentifierSelection subregion is executed then neither the TraverseSelection subregion or the NullTraverseSelection subregion are executed and no new context is created.
Traverse Identifier Example
Declare Manager entity:
Entity:Manager Attribute Text : Name Relationship Governs ->> Dog_Home Identifier:Manager_Name OwnKey Name
Declare Dog Home entity:
Entity:Dog_Home Attribute Text : Name Relationship Employs ->> Attendant Identifier:Dog_Home_Name OwnKey Name
Declare Attendant entity:
Entity:Attendant Attribute Text : Name Relationship Works_at --> Dog_Home Assigned_to ->> Kennel Identifier:Attendant_Name OwnKey Name ForeignKey Works_at : Dog_Home : Dog_Home_Name
Declare Kennel entity:
Entity:Kennel Attribute Number : Number Relationship Houses |>> Dog Identifier:Kennel_Number OwnKey Number
Declare Dog Owner entity:
Entity:Dog_Owner Attribute Text : Name Identifier:Dog_Owner_Name OwnKey Name
Declare Dog entity:
Entity:Dog Attribute Text : Name Relationship Belongs_to --> Dog_Owner Wears -|> Gps_Collar Identifier:Dog_Name OwnKey Name ForeignKey Belongs_to : Dog_Owner : Dog_Owner_Name
Declare GPS Collar entity:
Entity:Gps_Collar Attribute Number : Number Identifier:Gps_Number OwnKey Number
In the Manager entity state action context (as shown) or in any Manager context in another entity:
StateAction Traverse TraverseIdentifier:Dog_Home:Dog_Home_Name TraverseKey Dog_Home : Name : Dog_home_name NullIdentifierSelection | An object of Dog Home could not be found with the | supplied identifying attribute. Neither TraverseSelection | or NullTraverseSelection are executed. Template <<|>>Only the original context of Manager is available <<:>>in this subregion. Thus <<#Manager.Name>> is valid. TraverseIdentifier:Attendant:Attendant_Name TraverseKey Attendant : Name : Attendant_name Dog_Home : Name : Dog_home_name TraverseIdentifier:Kennel:Kennel_Number TraverseKey Kennel : Number : Kennel_number TraverseIdentifier:Dog:Dog_Name TraverseKey Dog : Name : Dog_name Dog_Owner : Name : Dog_owner_name NullIdentifierSelection | An object of Dog could not be found with the supplied | identifying attributes. Neither TraverseSelection or | NullTraverseSelection are executed. Template <<|>>Only the original context of Manager is available <<:>>in this subregion. Thus <<#Manager.Name>> is valid. Navigation Manager : Governs : Dog_Home Dog_Home : Employs : Attendant Attendant : Assigned_to : Kennel Kennel : Houses : Dog Dog : Wears : Gps_Collar TraverseSelection | All identifier specified objects were found when examined | and all conditional relationships (if any) were instantiated. Template <<|>>The following contexts are available: <<:>> <<#Manager.Name>> <<:>> <<#Dog_Home.Name>> <<:>> <<#Attendant.Name>> <<:>> <<#Kennel.Number>> <<:>> <<#Dog.Name>> <<:>> <<#Gps_Collar.Number>> NullTraverseSelection | Although identifier specified objects were found when | examined, one or more conditional relationships were not | instantiated. Template <<|>>Only the original context of Manager is available <<:>>in this subregion. Thus <<#Manager.Name>> is valid. |
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Copyright © 2017 Dark Matter Systems Ltd. All Rights Reserved. | |
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