Laddering Techniques

Laddering techniques involve the creation, reviewing and modification of hierarchical knowledge, often in the form of ladders (i.e. tree diagrams).

Here the expert and knowledge engineer both refer to a ladder presented on paper or a computer screen, and add, delete, rename or re-classify nodes as appropriate.

Laddering can also involve a set of predefined probe questions, such as "Could you tell me some sub-types of X?", "Could you tell me how you can tell that something is X?" and "Why would you prefer X to Y?". A leading proponent of this is Dr Gordon Rugg.

Use of Ladders

Various forms of ladder can be used.

• A concept ladder is particularly important since the way an expert categorises concepts into classes is an important key to understanding the way the domain knowledge is conceptualised.

• Laddering using an attribute ladder is another very useful technique. By reviewing and appending such a ladder, the knowledge engineer can validate and help elicit knowledge of the properties of concepts.

• Hierarchies with other relationships can also be used, such as composition ladders and process ladders described earlier. Validation of the knowledge represented in a ladder with another expert is often very quick and efficient.

For more explanation and examples of ladders, see types of knowledge models.

The Ladder Tool in PCPACK allows the creation of any type of ladder.