I read article about Types of Knowledge Discovered During Data Mining as the following: -
"Types of Knowledge Discovered During Data Mining. The term "knowledge" is very broadly interpreted as involving some degree of intelligence. There is a progression from raw data to information to knowledge as we go through additional processing. Knowledge is often classified as inductive versus deductive. Deductive knowledge deduces new information based on applying pre-specified logical rules of deduction on the given data. Data mining addresses inductive knowledge, which discovers new rules and patterns from the supplied data. Knowledge can be represented in many forms: In an unstructured sense, it can be represented by rules or propositional logic. In a structured form, it may be represented in decision trees, semantic networks, neural networks, or hierarchies of classes or frames. It is common to describe the knowledge discovered during data mining in five ways, as follows.
Classification hierarchies-The goal is to work from an existing set of events or transactions to create a hierarchy of classes. Examples: (I) A population may be divided into five ranges of credit worthiness based on a history of previous credit transactions. (2) A model may be developed for the factors that determine the desirability oflocation of a store on a 1-10 scale. (3) Mutual funds may be classified based on performance data using characteristics such as growth, income, and stability.
Clustering-A given population of events or items can be partitioned (segmented) into sets of "similar" elements. Examples: (1) An entire population of treatment data on a disease may be divided into groups based on the similarity of side effects produced. (2) The adult population in the United States may be categorized into five groups from "most likely to buy" to "least likely to buy" a new product. (3) The web accesses made by a collection of users against a set of documents (say, in a digital library) may be analyzed in terms of the keywords of documents to reveal clusters or categories of users."

The Question is
What the differrent between Classification hierarchies & Clustering ?