Understanding Post-Coordinate Indexing Systems

The question asks us to identify which of the given systems are based on the fundamental principles of post-coordinate indexing. To answer this, we need to understand what post-coordinate indexing is and examine each option provided: Chain Indexing, Peek-a-boo, Edge-notched card, and Duel Directories.

What is Post-Coordinate Indexing?

Post-coordinate indexing is an indexing technique where individual terms or concepts are assigned to documents during the indexing process. The coordination or combination of these terms to refine a search is done *after* the document has been indexed, typically at the time of searching or retrieval. This is in contrast to pre-coordinate indexing, where terms are combined into complex subject headings or strings *before* indexing.

Analysis of Each System

Let's look at each system listed in the options:

• (A) Chain Indexing: Developed by S.R. Ranganathan, Chain Indexing is a method used to create subject index entries for documents classified according to a faceted classification scheme like Colon Classification. In Chain Indexing, terms are arranged in a predetermined, hierarchical chain structure. The combination of terms (the chain) is established *before* searching. Therefore, Chain Indexing is a pre-coordinate indexing system.
• (B) Peek-a-boo (or Uniterm Indexing): Developed by Mortimer Taube, the Peek-a-boo system uses unit terms (single words or concepts) for indexing. For each term, a card is created. Document numbers are assigned to positions on these term cards. To search for documents indexed by a combination of terms, the corresponding term cards are superimposed. Holes punched at the same position across all cards "peek through," revealing the numbers of documents indexed by all the terms. The coordination of terms happens at the search stage. This makes Peek-a-boo a post-coordinate indexing system.
• (C) Edge-notched card: This system uses cards (often representing documents) with holes punched around the edges. Each hole can represent a specific characteristic, term, or concept. Information is recorded by notching out the edge of the card at the position of the relevant hole. Searching involves inserting a needle through the holes of a stack of cards at a specific position. Cards that are notched at that position will fall out, identifying relevant documents. To search for a combination of terms, multiple passes with the needle are made or specialized sorting devices are used. The coordination happens during the searching process. Thus, Edge-notched cards represent a post-coordinate indexing system.
• (D) Duel Directories (also known as Dual Dictionary or Coordinate Indexing): This system, also associated with Mortimer Taube and his colleagues, uses two lists or 'directories'. One list contains terms and, under each term, lists the document numbers indexed by that term. The second list contains document numbers and, under each document number, lists the terms assigned to it. Searching for documents indexed by multiple terms involves looking up the individual terms in the term-document list and comparing the document numbers to find common ones. The coordination of terms happens at the search stage. This is a clear example of a post-coordinate indexing system.

Identifying Post-Coordinate Systems

Based on the analysis:

• Chain Indexing (A) is pre-coordinate.
• Peek-a-boo (B) is post-coordinate.
• Edge-notched card (C) is post-coordinate.
• Duel Directories (D) is post-coordinate.

Therefore, the systems developed based on the basic principles of the post-coordinate indexing system are (B), (C), and (D).

The correct combination of systems based on post-coordinate indexing principles is (B), (C), and (D).

Revision Table: Indexing System Concepts

Additional Information on Indexing Systems

Indexing systems are crucial for organizing information resources and facilitating retrieval. They help users find relevant documents by providing access points based on their content.

• Manual vs. Automated Systems: Early post-coordinate systems like Peek-a-boo and Edge-notched cards were manual or semi-manual. Modern computer-based systems often utilize post-coordination principles, allowing users to combine keywords using Boolean operators (AND, OR, NOT) at the time of searching.
• Term Specificity: Post-coordinate systems often rely on uniterms or single concepts, which can sometimes lead to false drops (retrieving irrelevant documents) if not managed well, although term coordination at the search stage helps refine results. Pre-coordinate systems, with their structured subject headings, aim to be more precise initially but can be rigid.
• Evolution: The development from manual pre-coordinate systems to manual post-coordinate systems and finally to automated post-coordinate systems reflects the evolution of information storage and retrieval technology. While manual systems like Peek-a-boo and Edge-notched cards are less common today, the underlying principle of post-coordination is fundamental to modern database searching and web search engines.