A Quaestor knowledge based system can be divided into three parts:

1. The knowledge base: *.QKB;
2. A project file: *.QPF;
3. The Quaestor program; 

Both the QKB and the QPF are binary files that can be saved anywhere. There default location for Quaestor is defined in the personal user settings found in the menu dialog Tools>Options>Files.
Quaestor is an executable (requiring some additional libraries) that is usually installed on the workstation.

As a result, you can start Quaestor in three ways:

1. Double clicking the Quaestor program shortcut;
2. Double clicking the relevant knowledge base;
3. Double clicking the relevant project file;

What will follow will depend on the way a knowledge base is protected and the type of user license you have (see also User levels for more detail). 

Starting a project file

When you double click on a project file, Quaestor is automatically started with the knowledge base associated to the project file. For general start-up aspect of Quaestor, see Starting the Quaestor program below. When Quaestor is started, it will search for this associated knowledge base in the following sequence:

1. First Quaestor will try to open the knowledge base on the path given in the project file;
2. When the knowledge base is not found on this place, Quaestor will search in the knowledge base directory as stated in the Quaestor settings (Menu: Tools>Options>Files). 
3. When it cannot be found in this directory also, Quaestor will ask the user to select the knowledge base to be opened.

Please note that Quaestor will not check whether this is a valid knowledge base for the started project file.

Starting a knowledge base file

When you double click on a knowledge base file, Quaestor is automatically started. For general start-up aspect of Quaestor, see Starting the Quaestor program below. When Quaestor is started, it will depend on the User levels  and the knowledge base protection what will happen hereafter. 

1. When the knowledge base is not protected, it will be opened and be used in compliance with the defined User levels .
2. When the knowledge base is protected:
1. and the user is either a Domain Expert or End User, you are requested either to open an existing project file or start a new one. When you choose to open an existing project file or create a new project, a file dialog is presented and a project can be selected or created. Quaestor will start in the paths as defined for Reports, Projects and temporary files (Menu: Tools>Options>Files). When you cancel the dialog. Quaestor will close and exit.
2. and the user is a knowledge engineer, an additional request is presented to provide the password or to open or create a project file (and the process hereafter will be as described above).

Please note that Quaestor will not check whether the selected project is valid for the knowledge base.

Starting the Quaestor program

When you start the Quaestor program the following steps are taken:

1. First of all (Quaestor version 2.46.2 and higher, check version information here ), Quaestor will search for the Quaestor system settings file (QuaestorSystem.xml), which can be available in the Quaestor installation directory depending on the type of installation of Quaestor (see Quaestor Installation ):
1. by default, this Quaestor system settings file is not available. Quaestor will continue with searching for the the QuaestorSettingsFile.xml file in the default directory (see Directory structure ). QuaestorSettingsFile.xml defines the last used personal settings file (an xml file);
2. when the Quaestor system settings file (QuaestorSystem.xml) is available, Quaestor will read the license information from this file. Optionally Quaestor will read the defined path for setting files (QuaestorSettingsFile.xml and the personal settings file);
2. When the personal settings file (of which the file name is specified in QuaestorSettingsFile.xml...) is read successfully, all the personal settings are loaded. 
   It will depend on the availability of a default settings file (DefaultQuaestorSettings.xml) in the installation directory of Quaestor (see Quaestor Installation ), whether additional default settings are read:
1. by default, this file is not available and the personal settings as read are used;
2. when available, these default settings will overrule personal settings. 
3. In case default settings are found these will always be read and the resulting total settings are saved as PersonalQuaestorSettings.xml. 
   In other words, when default settings are available, these will always be used at startup of Quaestor. When you want to use personal settings other than these defined in the default settings, you have to select your personal settings file after Quaestor has started with these default settings. The only way to change this behavior is to delete the default settings file from your installation directory;
4. After all personal and default settings are read, Quaestor will first check the license by either contacting the Qnowledge license Manager or checking the string read in the QuaestorSytem.xml or personal settings file;
5. When a valid license is obtained, it will depend on the defined user level (either by the license or as set in the settings) what the next steps of Quaestor will be:
1. When the license or settings defines that you are an End User, Quaestor will either:
1. the default knowledge base as defined in (Menu: Tools>Options>Files), and hereafter will continue a described in "Starting a knowledge base file" above;
2. start Quaestor without a knowledge base;
2. When the license or settings defines that you are a Domain Expert or Knowledge Engineer, the Quaestor user interface will start in the default layout for the specified user level;

The above shows that when Quaestor is started, it will depend on the user level, protection and users settings whether only Quaestor is started, it is started with a knowledge base and a project or with a knowledge base only (only for Knowledge Engineers).