System analysis: ICANDO site safety
Engineer clicks on an icon. The cursor changes. 2 Engineer drops the icon on the backdrop. 3. The system records the location of the object.
We can begin to construct a sequence diagram and devise objects to s this Unlike the previous use case, this is quite detailed and technical in terms of the implementation. It is not unusual to get requirements as specific as this in technical domains. support
We need to decide whether we are going to model fine-grained objects such as an icon, or model coarser-grained objects such as a screen. Firstly, this is an analysis phase, so concrete detail for implementation should be outside of scope. Secondly, very fine detail can often be left to the implementation phase. Thus instead of modelling icons, cursors and backdrop explicitly, we shall simply consider a screen Thus we might make the first steps of our sequence diagram as in Figure 12.25″ Technically there will be lots of objects required to implement the above
sequence, but it is not the analyst’s job to decide those, nor is an analyst usually
knowledgeable enough to decide. Different implementation environments will
have different ways of achieving the same effect. Now we have to decide what to do about the creation of the feature. The simple thing is to create a feature directly from the screen. However, the creation of the feature also involves adding it to the site. The transaction is a little more complex than might at first be thought. Thus we shall use a control object to manage the actions, as in Figure 12.26. Thus the creation of the facility and the adding of the facility are managed by a
control object. Some analysts would put the logic all within the Facility and Site
objects or in the interface, and perhaps assign the creation of the feature to the
Site object, or the addition of the Facility to the Site object.
The entity classes for Site and Facility are as devised earlier and shown in Figure 11.26 when we determined objects by noun identification. The noun-identifica tion process is a perfectly good way of determining objects. However, objects drop whenever one occurs. A condition is indicated in square brackets, showing that the sequence step fires only if the condition is true. The resulting sequence diagram is shown in Figure 12.27. The edit control asks the site for two facilities, then searches the standard for an appropriate guideline. The guideline is then applied to the pair of facilities. If there is an infringement, an infringement object is created The Metalwho details of this matching and the pairing of objects will need much more analysis than been shown here This is quite a fiddly piece of code, and there will probably be questions raised during design that will need clarification, and further questions raised during implementation