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Describing the implementation in .NET Maker barcode 128 in .NET Describing the implementation




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Describing the implementation use .net framework code 128b generating tocompose code 128c in .net Java Reporting Library-Jasper Reports 3. The return type VS .NET code-128b of a sub-type operation must be the same as, or a sub-type of, the return type of the super-type operation12.

4. The parameter types of a sub-type operation should be the same as the parameter types of the super-type operation13. A discussion about behaviour conformance between types in the implementation model appears in chapter 8.

. 7.3.6 Meaning of in variants When we place an invariant on a type in an essential or specification model we mean that the invariant holds at all times.

This is reasonable because all state changing in these models is considered to be instantaneous. In an implementation model we need to take into account the time taken to process messages. State changing is not instantaneous.

Consider the share monitor example used earlier, whose type view is shown in figure 7.12. If we took a snapshot of this system during execution the type invariants of Sector and Exchange might not hold because one or more share objects might be in the process of changing their prices.

Type invariants in the implementation model can only show intention. If we were to cut off the stream of events being detected by the software system and wait until all the outstanding events had been processed completely, then the type invariants should hold. We cannot expect them to hold at all times during operation.

. 7.3.7 Visibilities barcode 128 for .

NET Mechanisms and, as we will see shortly, statecharts show messages being sent to objects. To send a message to an object we must know its identity. An operation knows the identity of an object to which it wishes to send a message either by:.

being passed the id entity as a parameter; obtaining it by navigating an association; obtaining it as a result from an updater or observer; itself creating the object.. 12The 13We principle of co-variant result types. don"t feel so stron visual .net barcode code 128 gly about this rule. Although perfectly type-safe, this rule might be considered overly restrictive.

It would be equally type-safe to allow contra-variant parameter types, where the parameter type in the sub-type is a super-type of the parameter type in the super-type. In the Eiffel programming language, parameter types can be co-variant but not contra-variant; this might not be theoretically type-safe but is claimed to be more useful in practice. Requiring the types to match exactly at least makes it clear when an operation is being overridden.

. 7.3 Type views of the implementation model If any operation of VS .NET barcode standards 128 an object type obtains an identity by navigating an association we say that the association is visible in the direction navigated. If we want, we can show this visibility by annotating the type view with an arrowhead on the association.

Figure 7.14 shows a simple mechanism and the related type view. In the mechanism the share object sends a message to a minder using the association called minder that exists between them.

The share must be navigating this association to find the identity of the minder: it requires visibility of the association. This is shown on the type diagram. What should we infer from the lack of an arrowhead at the other end of the association It would be wrong to infer that no visibility will exist between minders and mindables.

All we can say is that, given the sole mechanism shown in the diagram, visibility is not needed. The lack of an arrowhead means we haven t decided yet. As we add new mechanisms we can say more about the necessary visibilities.

When we extend the mechanism of figure 7.14 we introduce an additional visibility, as shown in figure 7.15.

It is useful to have a clear picture of the necessary visibilities because they influence the implementation techniques considerably. Sometimes we might want to revisit visibility decisions in the light of performance trade-offs or concurrency constraints..

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