This is an interesting thing. I love the tree so much. The Knowledge Tree here I mean is not referring to the Tree of Knowledge of Good and Bad.
Tree is a graph theory. The powerfulness of tree, is that almost any data structure can be represented into the tree. In order to store the data, we can use a single variable, for a single data. In order to store a list of data, we can use array and associative array (or hash, map, dictionary), list, vector, and others. Another powerful data structure which I like is the 2D array, especially used in matrix calculation. The 2D array represents the data in the table form. It is very useful in database. An image can also be treated as 2D array. Comparing the tree to the matrix, the tree is possible to represent the matrix (though it is not preferred).
Tree is mostly used in the programming, especially data representation such as JSON, XML, HTML, YAML, scene graph. Even the object (oriented) can be assumed as a tree, with the attributes and methods as the leaves, and the inheritance a parent-child relationship in the tree. Moreover, the programming languages can be parsed into parse tree and abstract syntax tree. The Python language is wonderful with the indentation syntax, which the indentation can be thought as the tree also.
In the decision support tools, the decision tree is used. In the pathfinding, such as depth first search, breath first search, A* search, these are also represented as graph and tree. In the file system, we have files and directories, these are also tree representation that is why the “/” is called the root directory. Furthermore, in the version control such as CVS, SVN, Git, Mercurial and else, they are also trees. That is why there are trunk and branches in the versioning system. In a document, we have heading 1, 2, 3, and so on with the body text. This makes our documents also a tree structure.
As a result, by combining these together, especially Python’s indentation syntax, I am creating my knowledge base using the tree forms. This is easy because creating something like concept map needs image editor software, it is time consuming. So, just using a plain text editor, with indentation, this helps me to manage my knowledge easier.
Text editor File quit, open, save buffers (open multiple files) Edit insert, delete, select (or highlight) cut, copy, paste (or yank) find, find next, find previous search and replace (with regular expression) undo, redo Others macro windows (split) mark folding syntax highlighting autoindent
The above is an example of my knowledge node, which is a text editor with the generic features. The next one is about the data types of database.
Database Null Numeric Integer bool int, tinyint, samllint, mediumint, bigint bit Real float double String Text datetime date time timestamp varchar, char enum, set Blob