
Representing External Applications
You can represent applications that are referenced by other applications but that are not implemented in your solution nor planned for deployment as part of any application systems that you design and compose from applications in the solution. Though these applications are called "external" because they are technically external to a system in the context of implementation and deployment, you can still include these applications as part of a system design. Including external applications in a system makes it possible for you to validate communication pathways to and from these applications when you define and validate deployment for the system. When the system is eventually deployed, references to external applications must be resolved with the actual deployment location of these applications.
The applications that you can represent as "external" include the following:
External Web services.
BizTalk Web services.
Databases
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Though databases are represented as "external" and have no support for implementation, there is no requirement or implication that databases are not deployed with the systems that use them.
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The following sections contain more about these external applications.
Representing External Web Services and BizTalk Web Services
You can add external Web services and BizTalk Web services to the application diagram by using the ExternalWebService and BizTalkWebService prototypes. In Distributed System Designers, the creation and behavior of external Web services and BizTalk Web services is the same. The BizTalk Web service application type makes it possible to document a referenced Web service that is known to provide access to a BizTalk application. In addition, infrastructure architects can use Logical Datacenter Designer to define application hosting constraints that selectively enable or disable hosting of external Web services and BizTalk Web services on specific logical servers.
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Though the procedure for defining a BizTalk Web service is the same as defining an external Web service, make sure that the referenced Web service is actually a BizTalk Web service.
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When you add a BizTalk Web service or external Web service to the application diagram, you must specify the location of a WSDL file that describes the Web service. After the external Web service or BizTalk Web service is added to the diagram, you can view its Web service operations; however, you cannot edit those operations.
For more information, see the following topics:
Representing Databases
You can add databases to the application diagram by using the ExternalDatabase prototype. Adding an external database to the application diagram makes it possible for you to document the existence of a database, visualize connections to it, and most importantly, create database consumer endpoints on connected applications. You can then configure a database connection string for each database consumer endpoint to create the appropriate entry in the consumer application's configuration file, which is generated once the consumer application is implemented. For more information, see How to: Configure Connections to External Databases.
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External databases make it possible for you to document references to databases. There is no requirement that database connection strings for database consumer endpoints that are connected to the same database need to be the same or specify the same physical database, although it is a best practice to make sure that they do.
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