In general, the view from which a work was written is less important than the actual contents of the work. In the list below, a number of content keywords are explained in more detail. A concise list of subject headings is included in the Reference section.
- 1 General works (d001)
- 2 Book studies and library science, writing (d004)
- 3 Christian practice (d012)
- 4 History (d014-d030)
- 5 History in general (d014)
- 6 History: the Netherlands (d017)
- 7 Linguistics and Literature (d031-d043)
- 8 Veterinary medicine (d056)
- 9 Agricultural science (d057)
- 10 Education (d072)
- 11 Law (d075)
- 12 Public administration (d076)
General works (d001)
- Collected works on a diverse range of topics, even if from the same author, as well as general collections of letters, receive the code d001 for general works.
- Collections of letters on one subject do not receive this code, but receive the code of the subject they treat.
Book studies and library science, writing (d004)
This code is also added to book auction catalogues and printer/publisher's lists or catalogues.
Christian practice (d012)
This category is only added to works strictly concerning what the church does with the doctrine, both organisational (church government/council, ecclesiastical offices, canon law) as regards to content (liturgy, sermons, catechisms). In other words, a prayer book falls under the category d011 for Christian doctrine, unless it is clear that it was used during church services. Then it will (also) receive the code d012.
- Historical works such as Tacitus or for example the Rijmkroniek [chronicle in rhyme] by Melis Stoke, fall under history and not under linguistics and literature (code d031-d043).
- Poems, sermons, speeches, etc. about historical events also receive a code for history (as specific as possible).
- Wedding songs, laudatory poems for a promotion, eulogies and similar occasional writings are also categorised under history (as specific as possible). They do not receive a code for linguistics and literature. They do, however, also receive the code d909 for occasional writings, and, if relevant, also for poetry (d917).
- Poems in praise of monarchs and other public dignitaries also fall under history and not linguistic and literature. They also receive the code d922 for period documents.
History in general (d014)
Numismatics, genealogy and heraldry also fall under this category.
History: the Netherlands (d017)
The lands or regions in the keywords for history and for linguistics and literature reflect the current national states and regions. So the term 'the Netherlands' only indicates the territory of the present Netherlands.
Linguistics and Literature (d031-d043)
- This category rules out other classifications. If, for example, one adds the keyword d035 (Dutch), then the more general keywords d031 (general linguistics and literature) and d032 (linguistics and literature in general) are excluded.
- Historical works receive a code for history but not for linguistics and literature, even though the considered work might be fully in verse. In that case, the work does receive the code for poetry (d917).
- Wedding songs, laudatory poems for a promotion, eulogies and similar occasional writings are categorised under history and not under linguistics and literature. The same holds true for poems in praise of monarchs and other public dignitaries.
Veterinary medicine (d056)
Works concerning animal husbandry fall under d057 (agricultural science). When, for example, the aspect of animal care dominates, the work receives the keyword d056 (veterinary medicine).
Agricultural science (d057)
- Works concerning horticulture and the growing of fruit and vegetables receive this code d057 for agricultural science. Gardening in the sense of landscape architecture receives the code d045 for particular arts.
- Tips for the small scale, private kitchen/vegetable garden fall under d058 for home economics.
Elementary school/text books, abc's, arithmetic books, Latin grammars and similar works, receive the code d072 for education.
- Official publications of court orders receive the code d075 as well as the document type code d922 for period documents.
- Notarial deeds also receive the code d075 for law.
Public administration (d076)
- Government publications concerning treaties and the issuing of rules, receive the code d076.
- Diplomatic acts, letters, rapports and similar items, however, fall under a history category (d014-d030).