4  Solutions to the Exercises

• 2.1

  2017-08-25: This step can be skipped with the current version of ConceptBase because the user interface now automatically connects to a ConceptBase server (CBserver). If it does not find a server, it tries to start it up on the fly. So, in most cases you do not need to bother with starting up a CBserver. Still, it is possible to start up a CBserver seperately and then start the user interface and connect to it.

  Enter in the same command window the following command:

  cbserver -port 5544 -d TutDB
  

  You can also use the option -db instead of -d:

  cbserver -port 5544 -db TutDB
  

  In this case, ConceptBase will maintain the Telos source representation of all objects in the database directory TutDB. Your own definitions will go to the file System-oHome.sml, because that is the default database module when you log into a ConceptBase server.

  
  An alternative to starting the ConceptBase server from the command line is to start it from CBIva. To do so, start CBIva and the select the menu item File / Start CBserver. A window like in figure 3 will pop up and you need to change the following parameters:

  1. The port number could be changed to 5544 but you can also leave it to 4001.
  2. Enter the path of the database TutDB; it is sufficient to replace the last two characters db by TutDB. But remember the whole directory path.
  3. Change source mode to on. This is equivalent to the -db option above.
  4. Change update mode to persistent.

  Then press "OK" to let CBIva start a ConceptBase server with the specified parameters and connect to it.

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  Figure 3: Start CBserver from CBIva

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• 2.2

  2017-08-25: This step can also be skipped since CBIva auto-connects to a CBserver.

  Select "Connect" from the File menu. An interaction window appears, querying the host name and the port number of the server you want to connect to. Enter the name of the host the ConceptBase server was started on and the port number specified by the -p parameter, then select "Connect". If you started the ConceptBase server on the same computer as CBIva, then use ’localhost’ as hostname.

  
  
  

• 3.1

  Department in Class
  end
  

  
  

• 3.2 To load an object from the database into the editor-window, select the frame button with tooltip "Load an object from CBserver" of the button panel or the option Load Object from the Edit menu. You should have a similar view as displayed in figure 4.

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  Figure 4: CBIva Telos Editor

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• 3.3

  Department in Class with
       attribute
              head: Manager
  end
  

  
  

• 3.4

  Lloyd in Manager end
  Phil in Manager end
  Eleonore in Manager end
  Albert in Manager end
  
  Production in Department with
    head
      head_of_Production : Lloyd
  end
  
  Administration in Department with
    head
      head_of_Administration : Eleonore
  end
  
  Marketing in Department with
    head
      head_of_Marketing : Phil
  end
  
  Research in Department with
    head
      head_of_Research : Albert
  end
  
  Lloyd in Manager with
    salary
        LloydsSalary : 100000
  end
  
  Phil in Manager with
    salary
        PhilsSalary : 120000
  end
  
  Eleonore in Manager with
    salary
      EleonoresSalary : 20000
  end
  
  Albert in Manager with
    salary
      AlbertsSalary : 110000
  end
  
  

  
  

• 3.5

  Michael in Employee with
    dept
      MichaelsDepartment : Production
    salary
      MichaelsSalary : 30000
  end
  
  Maria in Employee with
    dept
      MariasDepartment : Administration
    salary
      MariasSalary : 10000
  end
  
  Herbert in Employee with
    dept
      HerbertsDepartment : Marketing
    salary
      HerbertsSalary : 60000
  end
  
  Edward in Employee with
    dept
      EdwardsDepartment : Research
    salary
      EdwardsSalary : 50000
  end
  
  

  
  

• 3.6

  Figure 5 shows the ConceptBase graph editor on object Employee. The attributes of Employee and its instances are expanded using the menu of the right mouse button clicked on Employee.

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  Figure 5: CB Graph Editor on object Employee

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• 3.8

  Employee with
  constraint
    salaryIC: $ forall e/Employee m/Manager x,y/Integer
   (e boss m) and (e salary x) and (m salary y) ==> (x <= y) $
  end
  

  
  

• 3.11

  QueryClass BossesAndEmployees isA Manager with
  computed_attribute
      emps : Employee;
      head_of : Department
  constraint
      employee_rule:
         $ (~head_of head this) and (~emps dept ~head_of) $
  end
  

  Figure 6 shows parts of the answer to the query BossesAndEmployees.

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  Figure 6: Display of answers of BossesAndEmployees

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• 3.12

  Select the option "Stop CBserver" from the "File" menu of CBIva. Afterwards, stop CBIva via the "Exit" option in the same menu. If you started the ConceptBase server with the -db option (or with source mode set to ’on’), then you find the sources of your definitions also in the directory TutDB, see file System-oHome.sml. Open this file with a text editor such as WordPad.