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As mentioned earlier these tutorials are focussing on providing the basic skills of knowledge engineering. In this first tutorial, the main dimensions of a ship will be systematically varied. The knowledge used is Archimedes’ Law in combination with design requirements, which are the following:
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Before starting with your knowledge engineering, please make sure you are actually using the knowledge engineering user level and you have Quaestor configured in the most convenient layout.
To check/change your user level go to the general tab of Tools>Options. You can change your User level. If you are not able to change it to Knowledge Engineer (level 3), you do not have KE rights. Please contact your ICT department or Qnowledge for the proper license.
Furhtermore, for editing all kinds of properties it is convenient to use the Frame Viewer. Therefore in the Appeareance tab of Tools>Options select "Use classic frame viewer".
3 Creating parameters
When Quaestor is When Quaestor is started, an empty knowledge base is automatically created.
In the Knowledge browser, minimize the Quaestor Quaestor node, and expand the NewQkb node (figure 1).
Figure 1 Expanding the Newqkb node
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in the right-hand side of the knowledge browser, and select New Parameter/Function(Ctrl+I), see figure 3. Note that the last parameter in focus will be shown in the input field (most probablyprobably QKnowledgebaseVersion). Delete this parameter, type Lpp and click the Value button. Repeat these actions for the parameters B and T.
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The red cross is a sign that the parameter is not yet fully defined for the system.
In Quaestor, a valid parameter has:
- A unique name;
- A dimension (or assigned dimensionless);
- A way to be determined: input from the user or defined by a relation.
The first requirement is already satisfied, so let's assign dimensions to the parameters.
In the larger area of the Frame Viewer, a reference can be assigned to the parameter. A proper reference is important, as users of the knowledgebase may not be certain of the exact meaning of the parameter. Please also read Documentation of knowledge for more details.
Figure 4 In the Frame Viewer, a dimension and reference can be assigned to the parameter
NOTE: The dimension of a parameter can also be assigned in the Slots & Properties window. Just scroll down to the Dimension row, and change the value.
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Figure 5 Let Quaestor know Let Quaestor know how a parameter should be determined
Notice that the status of LPP has changed to
to show that Quaestor knows that Quaestor knows enough about this parameter to use it in a computational model.
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Note that above you have explicitly added Lpp, B and T as parameters to the knowledge base.
You are also able to implicitly add parameter by creating relations that contain new parameters. Quaestor will Quaestor will automatically add these new parameters to your knowledge base (so implicitly). You will see this next.
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Note that when you enter a relation, Quaestor provides Quaestor provides as much help as possible by means of the Help Checker. This checker shows what to expect (in this case a Value or an Expression, ValExp). After saving a relation, the Help Checker will check the syntax for possible errors, and shows a warning message when something is wrong.
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The following might seem a bit unconventional: a second relation is given for Rho. This is a nice example of how quaestor works: In a calculation, Quaestor can Quaestor can find numerous calculation paths and automatically chooses the most appropiate one based on constraints and available data. An infinite number of relations can be assigned to one particular parameter.
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The constraint is now added, and a parameter named Watertype$ has been created. The $ at the end of the parameter name makes sure Quaestor recognizes sure Quaestor recognizes it as a String value, and the dimension Str is automatically assigned (see also Quaestor syntax. We have to assign a determined by value to make it a valid parameter.
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Both relations are now connected to the corresponding watertype by means of the value of the string Watertype$. Note if Rho is needed in the calculation progress, Quastor will note that the watertype is needed and will ask the user for this value (because it is assignedUser Only).
TIP: By selecting a parameter in the knowledge base and then double clicking the box below the knowledge base tree, the relations defining that particular parameter are visible (figure 8).
Moreover, when you select a relation in the knowledge base, and double click that box, the parameters that can be calculated by the selected relation are shown.
When single clicking the box, all connections to the parameter or relation are shown. See also information on the Knowledge Browser.
Figure 8 When selecting a parameter and double clicking the box indicated by the blue arrow, all relations defining that parameter are shown.
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The use of a dropdown box will be clear in a later stage of this tutorial, when calculations are made. Note that you can add thethe @EQEXPLAIN attribute to the data slot of the Watertype$ parameter (see Frame Viewer for data slot) in order to manipulated that only "Saltwater" and "Freshwater" are shown (so without SW and FW).
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8 Creating a solution
Let's perform our first Quaestor calculation. A solution is always determined by one or more Top Goals. A top goal is a parameter (or object) that is your final calculation target, in this tutorial it's the displacement of the ship.
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button when you use classic buttons or use classic buttons or the "Create Solution" button when you use thethe Workbase buttons to start the calculation with top goal DISP.
The calculation progress is started, and Quaestor first and Quaestor first collects all input data (figure 10).
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As mentioned in the objective, we'd like to create a dataset of systematically varied ships. We could of course perform several calculations with different input data by hand, but it's much easier to use the ability of Quaestor to of Quaestor to create multiple case solutions. To keep the complexity of this example within reason, we will only vary the breadth and length of the vessel. Please note that due to some important conceptual reasons the latest Quaestor release latest Quaestor release can only perform calculations on ranges of parameters when you alreade have created a solution.
B= 9(0.5)11 m Lpp= 55(2)69 m
In this way, B and Lpp are defined by a range, given the start value, step size and end value. For example, Lpp is defined from 55 to 69 meter, with steps of 2 meter.
Quaestor will Quaestor will ask if it should create a case matrix for Lpp (figure 15), click yes (an explanation will follow).
Figure 15 Quaestor asks 15 Quaestor asks if a case matrix should be created
You will see that the single value input is still in the list and the multi case values are in the table part of the Workbase. Press the button or "Accept input & Continue" button to continue.
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