Tutorial 1 Getting started
| Learning goals
| Prior knowledge |
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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Our objective is to generate a dataset of systematically varied ships that meet the design criteriarequirements.
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 Tools -> Options -> General. 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.
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When a knowledgebase node is expanded, like Newqkb
here, the classes within the knowledgebase are visible. Classes are used to organise your data and equations, and put them in a practicable structure. In Quaestor, all data is put in parameters. You can designate one (or more) parameter as the goal of the calculation.
Note |
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Classes are a means for organizing parameters for the user. They are not to be confused with a class in object oriented computer programming. The Quaestor core does not use the classes at all.It only uses the parameters! |
the knowledgebase are visible. Classes are used to organise your parameters, and put them in a practicable structure. The Top Goals/Undefined class is part of the knowledge base by default. Here, the goal parameters of your calculation (Top Goals) can be stored, as well as other parameters that don't belong to other classes (Undefined).
Create a new class, named Main Dimensions, in which the following ship parameters are to be stored.
Lpp: Length between perpendiculars
B: Moulded breadth
T: Draught from keel to Construction Water Line
Main Dimensions
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The class is now shown in the knowledgebase tree, and you can add the parameters Lpp
, B
and T
.
Main Dimensions
and select Knowledge -> New parameter/function from the main menu. Alternatively, click in the right part of the knowledge browser, and select New Parameter / Function (Ctrl+I). Give the parameter the name Lpp
and click the Value button to select its type. Repeat these actions for the parameters B
and T
.The added parameters now appear in the right part of the Knowledge browser like this:
A red cross draws your attention to the fact that a parameter is not yet fully defined for the system to use it.
The first requirement is already satisfied, so let's assign dimensions to the parameters.
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into m
, the dimension for Lpp
(meters)....
B
and T
, just as described above. Of course, the breadth and depth of the ship are defined in meters.Now only the last requirement for valid parameters has yet to be fulfilled: a way to be determined (input from the user or defined by a relation). This qualification can be provided in the Properties window.
Lpp
. In the Properties window, scroll down to the Determined by row. Change the value to VR: User only, as the parameter Lpp is input (instead of defined by a relation)....
to show that Quaestor knows enough about this parameter to use it in a computational model. Now make sure that B and T are determined by VR: User only too. By the way, VR stands for Value RequestedBy the way, VR stands for Value Requested.
Note |
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If a parameter still shows a red cross when you have provided all needed property values, click on Top Goals/Undefined, and you will see the blue cross. |
Note that above you have explicitly added Lpp
, B
and T
as parameters to the knowledge base. You are also able to implicitly add parameters by creating relations that contain new parameters. Quaestor will automatically add these new parameters to your knowledge base (so, implicitly). You will encounter this in the following section.
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Rho = 1025
(belonging to salt water), and click Save:
Note that when you enter a relation, 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.
Because of entering the relation, the parameter Rho
has automatically been created. For Rho
to be a valid parameter, a dimension should be assigned.
Noteinfo |
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The parameter is automatically created in the Class in focus when saving the relation! |
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Rho
and assign it the dimension kg/m^3
. Rho
is now a valid parameter. Furthermore, make sure Rho
is determined by SYS: System/Equation, as a relation is used to determine Rho
.What follows now 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 find numerous calculation paths and automatically chooses the most appropiate one, based on constraints and available data.
Noteinfo |
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An infinite number of relations can be assigned to one particular parameter. |
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Rho = 998
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Rho = 1025
in the Knowledge browser and select Constraint -> Add New. In the upper part of the new window enter the following constraint:Watertype$ = "SW"
and click Save:
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 it as a String value, and the dimension Str is automatically assigned (see also Quaestor syntax). You have to assign a Determined-by value to make it a valid parameter.
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Repeat the process for the other relation.
Watertype$ = "FW"
...
to the relation Rho = 998
.
Note that the expression editor assists you with the presentation of existing parameters and intrinsic functions.
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Whenever Rho
is needed in the calculation process, Quaestor will note that the watertype is needed to determine the value of Rho
, and will ask the user for this value (because it is assigned to be User only).
When you select a parameter in the upper list, the relations of that particular parameter are visible:
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Because there are only two possible values for Watertype$
(SW or FW), it's easy to integrate a dropdown box.
Watertype$
in the Knowledge Browser, select the Parameter tab in the Properties window and in the Reference box enter the following lines:FW<EQ>Fresh Water
SW<EQ>Salt Water
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 the @EQEXPLAIN attribute in the Data box ('data slot') of the Watertype$
parameter (see Frame Viewer for data slot) in order to display only "Salt Water" and "Fresh Water" are shown in the dropbox (so without SW and FW).
On the basis of the earlier defined parameters and the block coefficient Cb
, the displacement of the ship can be calculated.
DISP = Cb * Lpp * B * T * Rho / 1000
which defines the displacement of the ship in tons.
Note that two new parameters are created: the block coefficient Cb
and the displacement DISP
. In order to keep the knowledgebase meaningful, it is necessary to provide references, dimensions and determined-by values for these parameters.
Cb
and DISP
. Cb
has no dimension (-), DISP
should be in tons (t). Just press OK if Quaestor warns that tons is no base dimension (kg), it is just to inform you. We covered this by dividing DISP
by 1000. The determined-by values should be VR: VR User Only for Cb
, and SYS: System/Equation for DISP
, as the block coefficient is input and the displacement is determined by a relation. Verify that all parameters now have a blue cross instead of a red one in front of them:Let's perform your 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.
DISP
....
B = 10 Cb = 0.55 Lpp = 60 T = 6 Watertype$ = SW (Salt Water)
Note that the input of Watertype$
consists of a dropdownbox, which you created above:
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After providing the data you have to press the Next button to continue. The actual calculation is started now and because this is a very simple example, the final state is alost almost immediately shown:
The top goal (DISP
) is shown, together with all parameters that were used for the calculation. With these input values, the displacement of the ship is about 2030 tons.
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As mentioned in the objective, you will create a dataset of systematically varied ships. You could of course perform several calculations with different input data by hand, but it's much easier to use the ability of Quaestor to create multiple case solutions. To keep the complexity of this example within reason, you will only vary the breadth and length of the vessel. Please note that due to some important conceptual reasons, the latest Quaestor release can Quaestor can only perform calculations on ranges of parameters when you already have created a solution.
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B= 9(0.5)11 Lpp= 55(2)69
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.
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Info |
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Ranges can be defined in multiple ways:
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As it is, the multiple case solution table is sorted by the breadth of the ship. Now suppose you'd like parameter Lpp
to be the leading parameter in this table.
Lpp
. In the Properties window, scroll down to the row Output to, and select HEADER. Now, refresh the table of the multiple case solution by clicking another solution, and then again the multiple case solution. The table is now headed by Lpp
.A lot of cases in your solution don't meet the design criteria: a displacement between 2000 and 3000 ton. We could have fixed this by adding a constraint to DISP
, but another way is to use a filter in the solution table.
DISP
solution, and click the Filter button. The Filter window shows. For DISP
, select Range as filter, fill in 2000 for Lower bound and 3000 for upper bound. Click the Apply button....
Now, only the cases for which 2000 < DISP
< 3000 are shown in the table. The objective of this tutorial is now completed: you built a dataset of systematically varied ships that meet the design criteria.
You can verify your results by comparing it to [Tutorial 1 Finished] .