About View Object and View Link Instances

One of the primary functions of an application module is to provide a client with the data it needs to complete a specific task. This data can be represented by a tree, called the application module's data model , which in turn contains view object and view link instances. For more information on application modules, see the related topics list.

View Object Instances

A view object instance manages a single cache of retrieved data. View object instances use data retrieval mechanisms (usually SQL queries) provided in view object definitions. However, these mechanisms can be customized on an instance level; by dynamically adding or changing clauses in the query of one view object instance, you do not automatically make similar changes in other view object instances, even if the instances share a definition. Moreover, executing a query on one

All view object instances have a name assigned to them when they are first added to a data model. This name is used by clients and service methods to access the instance and the data stored in the instance's cache. This name is not necessarily related to the view object definition name. For example, the same data model could contain two view object instances, called AllOrders and OrdersForCustomer, based on the same view object definition, called OrdersView.

View Link Instances

A view link instance provides a master-detail relationship between view object instances. View link instances are based on view link definitions, which relate the relevant view object definitions.

Adding a view link instance to the data model puts two view object instances in a master-detail relationship; removing the view link makes the detail view object instance completely independent.

All view link instances have a name assigned to them when they are first added to a data model. This name is used by clients and service methods to access the view link, which is primarily useful for removing it. This name is not necessarily related to the view link definition's name. For example, if the following hold:

There is a view link definition called CustOrdLink, which relates the view object definitions CustomersView and OrdersView
CustomersView has two instances in the data model: AllCustomers and CustomersForSalesContact
OrdersView has two instances in the data model: OrdersForUnrestrictedCustomer and OrdersForCustomerByContact

Then there can be two instances of CustOrdLink in the data model:

CustOrdLink1, which makes OrdersForUnrestrictedCustomer a detail of AllCustomers
CustOrdLink2, which makes OrdersForCustomerByContact a detail of CustomersForSalesContact

Instances of Bidirectional View Links

If a view link definition is bidirectional, particular instances of that view link must pick a direction. However, an instance can use either direction. For example, if the following hold:

There is a bidirectional view link definition called ItemsWarehouseLink, which relates the view object definitions ItemsView and WarehousesView
ItemsView has two instances in the data model: AllItems and ItemsForWarehouse
WarehousesView has one instance in the data model: WarehousesForItem

Then there can be two instances of ItemsWarehouseLink in the data model:

ItemsWarehouseLink1, which makes WarehousesForItem a detail of AllItems
ItemsWarehouseLink2, which makes ItemsForWarehouse a detail of WarehousesForItem