Roles

Roles and types are identified by a non-negative integer index. Every process has one current role, and every user has one default role.

• currentrole$_{tn}$(p:process):role := current role of process p at time n
• defrole$_{tn}$(u:user):role := default role of user u at time n

The first system process 0 gets the default role of user 0.

$$\mathrm{currentrole}_{t0}(0) := \mathrm{defrole}_{t0}(0)$$ (1)

In the default setting, i.e., if not specified differently by the Initial Role or the Forced Role attributes of the program file or the process (see subsection 3.5), the following implicit role transitions are performed:

• All subprocesses inherit the current role of their parent process.
  

  $$\mathrm{clone}_{tn}(\mathrm{p}_1,\mathrm{p}_2) \Rightarrow\ ... ...tn+1}(\mathrm{p}_2) := \mathrm{currentrole}_{tn}(\mathrm{p}_1)$$ (2)

  
  

• On every change of the process owner, the process current role is set to the new owner's default role.
  

  $$\mathrm{changeowner}_{tn}(\mathrm{p},\mathrm{u}) \Rightarrow... ...trole}_{tn+1}(\mathrm{p}) := \mathrm{defrole}_{tn}(\mathrm{u})$$ (3)

  
  

• When another program is executed, the current role of the process is kept.
  

  $$\mathrm{execute}_{tn}(\mathrm{p},\mathrm{f}) \Rightarrow\ \m... ...e}_{tn+1}(\mathrm{p}) := \mathrm{currentrole}_{tn}(\mathrm{p})$$ (4)

  
  

Thus, the default scheme follows the expected behaviour of a role based model.