Modelling Human Factors using the Systems Modelling Language

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HFIDTC/2/WP2.8.9/1Version 2/ 24th September 20087.2.2.1 Value addedThe production of the Sequence and Activity Diagrams above has added further to ourunderstanding of the requirements, and has prompted us to begin considering the Postswithin the Organisational Units, the organisational structures within them and theprocesses, procedures and tasks that will be needed to support them. The decision toassign these activities to the Post of Ground Commander in the GCS raises the questionof whether only the Ground Commander will be able to perform these activities, or ifother, yet to be considered, Posts will be able to do them as well, and if so, in whatcircumstances. It also prompts us to think about the organisational structure of the Postswithin the GCS, and the processes and procedures that will have to be established for theinteractions between the various actors around these specific activities. Theseconsiderations are a view of the H-Fly system that is represented by HV-D. At this earlystage in our modelling we are unable to provide many details on these issues, but we canput the framework in place that will be used to capture them as the design continues.By adopting terms such as ‘Organisational Unit’ and ‘Post’ that are defined in the HumanViews Handbook, using these terms to stereotype entities in our model and by populatingthe Glossary of terms, we have started to provide definition for our model and promotecommon understanding.The Activity Diagram will be useful at a later stage when we start to allocate functionsbetween the hardware/software and the humans, and in the design of the User Interface(UI) which will support the activities (see Section 7.2.6).7.2.3 Modelling UsersHaving established that there will be a Post called ‘Ground Commander’ that resides inthe GCS, and specified some of the activities to be performed by that Post, we can useanother SysML Diagram, the Block Definition Diagram, to document what we know /have assumed so far.According to the OMG SysML Specification:“Blocks are modular units of a system description, which defines a collection of featuresto describe a system or other elements of interest… Blocks provide a general purposecapability to model systems as trees of modular components”.The Block Definition Diagram defines features of blocks and associations between them,which are shown as connecting lines.24
HFIDTC/2/WP2.8.9/1Version 2/ 24th September 2008Figure 7-6 - Initial Block Definition Diagram of PostsHV-F requires that we consider the mapping between Roles and Tasks. We know some ofthe activities that will be performed by the Post of Ground Commander, so we could nowconsider the Role that the person in that Post will be assuming when they perform thoseactivities. Let us say that the activities represented in the Activity Diagram above fallunder the Role of ‘Resource Allocator’. We can represent this as an Operation of theBlock ‘Ground Commander’ in our Block Definition Diagram above. We could alsocreate a Role of GCS Liason for the Post of Section Commander to cover the activities of‘Request SA information’ and ‘Provide details’ taken from our Sequence Diagram.HV-D requires that we consider rank / authority structures, and we have enoughinformation at this stage to make decisions on ranks for the various Posts; these areindicated on the diagram as Properties of the Blocks. Later on we may go into moredetail, for example determining that the HQ Commander will have a rank of Major orabove, in which case we will update the model accordingly.We have also created a Property of ‘Ground co-ordinates’ for the Section Commanderand Ground Troops, which has been derived from the Activity, ‘Determine requestor’slocation’. We know that the system will have to know the location of troops on theground in order to support this activity and this will be reflected in the System Views.25
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Modelling Human Factors using the Systems Modelling Language

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