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Namespaces
A namespace is a logical container in which all the names are unique; that is, a name can appear in multiple namespaces but cannot appear twice in the same namespace.
A namespace is, literally, a space in which to store some names. Namespaces provide a way to group artifacts, an abstract equivalent to folders in a file system. Each namespace should gather resources together that have some relationship to one another. In runtime processes, the unique identifier for an artifact is composed of the namespace and the artifact's local name.
You can see the namespaces for resources in the Business Integration view. Click the Show Namespaces button in the toolbar to show the namespaces of the resources.
The default namespace for an artifact is derived from the file path. You can change this default namespace, but make that change carefully. Read the rest of this topic and the related task "Changing a namespace" for more information.
It is valid to have more than one namespace in a module or library. However, there are conditions you need to avoid with namespaces:
- Do not split a namespace across two dependent projects.
- Avoid name collisions within a namespace.
Splitting a namespace
A single namespace should not be used in two dependent projects; each module or library requires its own set of unique namespaces.
You are likely to encounter problems if you use the same namespace for multiple modules or libraries. Consider this example. A module depends on two libraries that have artifacts with a common namespace. The module references Artifact A in one of the libraries and Artifact B of the same type in the other library. (Artifacts A and B could both be business objects, WSDL files, maps, or some other element.) If the library containing Artifact A is listed first in the dependency editor, the program can find Artifact A but not Artifact B. If the libraries are listed in the reverse order, the program will find Artifact B but not Artifact A.
The same problem will occur if a module that depends on a library has artifacts that have the same type and namespace as artifacts in the library. The program will find the artifacts in the module but not in the library.
IBM Integration Designer and IBM Process Server require that all artifacts with the same namespace reside in the same library or module. The same namespace should not be used by artifacts in two libraries or modules. IBM Integration Designer generates unique namespaces by default when artifacts are created.
Do not create artifacts with the same namespace in different projects.
If you encounter this condition, use the refactoring actions to either move the artifacts to the same project or to assign the artifacts different namespaces. It is a good practice to ensure that the namespace for an artifact shows the actual location of the artifact.
Name collisions
If you define two different business objects or interfaces with the same name and namespace, you will receive build errors. To remedy this problem, follow these steps:
- If the definitions are the same, delete one of them. Clean and rebuild your project. Correct any errors that might result by pointing existing business object or interface files to the file containing the definition that you did not delete.
- If the definitions are not the same and use both of the definitions in your migrated service, rename the definition name or the namespace. If there are only a few definitions in the entire file that are duplicates, then changing their names is recommended. If all of the definitions in the file are duplicates, then changing the namespace of all of the definitions is recommended.
- Clean and rebuild the project, ensuring that the artifacts that you want to use in the definitions that you modified reference the new definition name or namespace.
- When you have two import statements for the same namespace in an interface (WSDL file), you can remedy this problem by chaining the imports in such a way that one of these interfaces imports the other, which imports the next one, and so on., so that there is only one import for this namespace per interface. Then clean and rebuild the project.
Moving namespaces
You need to pay some attention to namespaces when you move artifacts from one library to another or from a module to a library. IBM Integration Designer and IBM Process Server require that all artifacts with the same namespace reside in the same library or module (see "Splitting a namespace" above). Artifacts in two dependent projects should not use the same namespace. Similarly, the same namespace should not be used for artifacts in a module and for artifacts in libraries on which the module has dependencies. When you move an artifact to a library, first change the namespace to reflect the new location, or at least change the namespace to one that is not being used by the original project.
Optimizing performance
If you are working with more than one business object, you can improve performance if you put each one in a separate namespace. If you put them all in the same namespace, all of the business objects will get loaded each time one of them is called, and the overall performance of the tool will degrade.