Subject Indexing

Subject Indexing

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Note: A subject index (also known as a subject directory, web directory or just a directory) is the online equivalent of an organized file cabinet.

Subject Indexing Guidelines


Indexing documents by a controlled index language aims at facilitating access to large literacy collections by describing subject content as precisely as possible. For that purpose, the indexer first has to understand fully the document’s content and then to select and assign the appropriate descriptors and additional vocabulary from the STW Thesaurus for Economics according to the indexing rules.

The indexing guidelines support the following objectives:

Subject indexing should be carried out in a way that retrieval results meet the users’ queries.
The results of subject indexing should be easy to understand by users regarding form and subject content.

Understanding content

At the beginning of the indexing process, it is crucial to understand the subject content of a document and to identify the main focus as well as less important aspects.

Browsing and content analysis
Document title, table of contents, summary, introduction, and conclusion/concluding remarks should be consulted to get a first impression of the content. Pre-assigned keywords and classification codes can also be used to understand the content. The content has to be analyzed and understood completely.
Describing main focus and secondary aspects
When a document is dealing with more than one topic, it is necessary to distinguish clearly main focus and secondary aspects.


When the indexer has analyzed the content of the document, he/she has to assign descriptors and further vocabulary according to the subjects treated. This assignment process is called indexing. Indexing vocabulary consists of descriptors, general terms, form or type of document, and, if necessary, free keywords and dates.

General conventions

Description of content
Indexing refers to the content of the document. It is not meant to be a mere succession of keywords from the text. If the meanings of title and text show any difference, it is the meaning of the text that has to be described.
Main focus and secondary aspects
The main focus of the document has to be covered completely by descriptors. Secondary aspects have to be indicated just in case innovative or rare facts/subjects are mentioned or in case facts/subjects are of special importance to a certain region or a certain topic.
Exception: Case studies
In case the document contains fundamental information on a region or an item that serve as an example, the region or item should be indexed. In addition, a broader term can be indexed as well. If any relevant information on the exemplary region or item is missing, only the broader region or item should be indexed.

Indexing with Preferred Concepts

One descriptor at least has to be assigned to each document.
Exception with subject descriptors: Assigning subject descriptors is not necessary, when type-of-document code plus geographic name, or personal/organizational headings are sufficient.
According to the principle of assigning the most specific term, the selected descriptors should describe the content as precisely as possible.
A broader term can be assigned,

when otherwise several narrower terms of the same hierarchical level would be necessary to describe the specific aspects mentioned in the document,
or when in a document with varied contents (e.g. collected edition) several aspects of a subject matter can be summed up by the broader term.

In case an expression cannot be described adequately by one descriptor alone, a combination of two or more descriptors can be assigned (postcoordination).
The resulting compound term should represent the professional linguistic usage for the underlying concept.

If a document refers to a regional context, at least one geographic descriptor must be assigned. The same goes, if the regional context is only included implicitly, as in case of political or legal subjects.

Indexing with general preferred concepts

General descriptors must always be assigned in connection with at least one subject descriptor.
They serve to describe a topic more precisely or as an additional information for retrieval purposes.

Indexing form or type of documents

Special codes are used to indicate form or type of document.
Descriptors, which are homonyms to one of the codes (e.g. Bibliography, Reference work) are exclusively used for indexing.
Exception: The descriptor “Statistical data” is also used to indicate statistical data collections.

Statistical data must always be indicated by code “Statistik” (#15).

It is possible to assign more than one code.

Indexing chains

Definition and purpose of indexing chains

By assembling indexing chains the main focus of a document is made clearer.
Indexing chains make it easier for users to understand the content of a document.

Sequencing in indexing chains

Whenever it is possible to determine a subject descriptor describing the most important topic of a document, it has to be written at the beginning of the chain.
The geographic descriptors follow behind their respective subject descriptors.
Broader and narrower terms can be indexed together, when they are of equal importance in the context.
General descriptors directly follow their respective subject descriptors.


Two descriptors forming a concept by way of postcoordination have to be written one after another.
The selected combination should be formed by the most specific terms.



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