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In a word, qualifiers are rules. Qualifiers define how much management should be provided by WPS for a component at runtime. A process application communicates its QoS needs to the WPS runtime environment by specifying service qualifiers. The qualifiers govern the interaction between a service client and a target service. Qualifiers can be specified on service component references, interfaces, and implementations and are always external to an implementation. The different categories of qualifiers include the following:

  • Transaction, which specifies the way transactional contexts are handled in an SCA invocation
  • Activity session, which specifies how Activity Session contexts are propagated. An Activity Session extends the concept of transaction, to encompass a number of related transactions.
  • Security, which specifies the permissions
  • Asynchronous reliability—rules for asynchronous message delivery

SCA allows these QoS qualifiers to be applied to components declaratively (without requiring programming or a change to the services implementation code). This is done in WID. Table 2.2 lists the different types of qualifiers, along with their qualifying values. Usually, you apply QoS qualifiers when you are ready to consider solution deployment. Look for more details about QoS, especially event sequencing, in Chapter 11.

Table 2.2. Adding References to the Application Deployment Descriptor


Qualifier Values

Reference qualifiers

Asynchronous reliability

Suspend transaction

Asynchronous invocation

Suspend activity session

Interface qualifiers

Event sequencing

Join activity session

Join transaction

Security permission

Implementation qualifiers

Activity session


Security identity

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