9 An Information System
Solutions
Implement an information system with hyperlinks and history of visited objects (similar to Wikipedia). Test this system on the following knowledge area from physics:
- Atom
- is the smallest constituent unit of ordinary matter
that has the properties of a chemical element.
Every atom is composed of a nucleus and
one or more electrons bound to the nucleus.
See also: [atomic nucleus, electron, nuclear power] - Atomic nucleus
- is the very dense region consisting of
protons and neutrons at the center of an atom.
Protons are positively charged while
neutrons have no electrical charge.
Atoms that differ only in the number of neutrons
are called isotopes.
See also: [proton, neutron, atom] - Electron
- is a stable, negatively charged elementary particle ...
See also: [atom] - Proton
- is a stable, positively charged elementary particle ...
See also: [atomic nucleus] - Neutron
- is a stable elementary particle without electrical charge ...
See also: [atomic nucleus] - Nuclear power
- is the use of nuclear reactors to release nuclear energy, and thereby generate electricity. Nuclear binding energy is the energy that would be required to disassemble the nucleus of an atom into its component parts.
The information system consists of terms (objects) that can be searched for. Explaining texts and references to other objects are attached to the objects. A possible representation would be:
object(
ID, /* unique identifier, a nummer */
Name, /* display name */
Text, /* list of text lines */
References). /* List of references to other objects */
Example:
object( 1, 'Atom',
['is the smallest constituent unit of ordinary matter ',
'that has the properties of a chemical element. ',
'Every atom is composed of a nucleus and '
'one or more electrons bound to the nucleus.'],
[2, 3, 4] ).
The user always gets an object with the explaining text and the references to other objects, e.g.:
Atom (ID=1)
is the smallest constituent unit of ordinary matter that has the properties of a chemical element.
Every atom is composed of a nucleus and one or more electrons bound to the nucleus.
See also:
2 - atomic nucleus
3 - electron
6 - nuclear power
The user can use the following commands:
| init | Initialize the history of visited objects to []. The history [3, 2, 1] means that the object 1 was visited first and the object 3 was visited last. |
| show_all | Show all objects with their identifiers. |
| show(ID) | Show the object with the identifier ID. Suppose the current history is [3, 2, 1]. If the system shows currently 3, then the new history becomes [ID, 3, 2, 1]. If the system shows currently 1, then the new history becomes [ID, 1]. |
| trace | Show the history of the displayed objects. |
| back | Move forward in the history and show the corresponding object. The history list is not changed. |
| fwd | Move forward in the history and show the corresponding object. The history list is not changed. |