The rule against adding one standard subdivision to another standard subdivision is complicated, as can be seen in this note at **T1—0 Table 1. Standard Subdivisions**:

Do not add one standard subdivision to another standard subdivision unless specifically instructed. Standard subdivisions may be added to special notation listed in the regular standard subdivision sequence, to subdivisions of T1**—**04 Special topics that are specifically listed in the schedules, and to displaced standard subdivisions wherever they appear. Numbers in the schedules that look as though they were built with notation from this table but are outside the regular sequence of standard subdivisions are not considered “standard” subdivisions. Hence notation from Table 1 may be added to such schedule numbers

The Introduction (section 8) expands on this instruction with examples, but the matter is still difficult. What is the simplest way to determine whether it is OK to add a standard subdivision to a specific number in WebDewey? Look for the Synthesized number components box, newly introduced in a September 2018 WebDewey update.

(1) If the Synthesized number components box shows that the number was built with standard notation from Table 1, then it is forbidden to add another standard subdivision. For example, **370.1 Philosophy and theory, education for specific objectives, educational psychology** has this Synthesized number components box:

Similarly, **370.14 Communication **has this Synthesized number components box:

The presence of a class-here note in a record for a number built with standard notation from Table 1 does not grant permission to add another standard subdivision. For example, **535.220287 Testing and measurement** has the class-here note “Class here photometry” to show that the standard subdivision has an extended meaning in context; but the Synthesized number components box makes clear that the number was built with standard notation from Table 1, and no second standard subdivision may be added to **535.220287**.

(Some regular standard subdivisions have instructions for adding special notation to the standard subdivision, e.g., **T1—08 Groups of people** and **T1—093-T1—099 Specific continents, countries, localities; extraterrestrial worlds. **Following those instructions where they exist in Table 1 is not the same thing as adding one standard subdivision to another standard subdivision.)

** **(2) If there is no Synthesized number components box for the number, then standard subdivisions notation may be added. The Introduction cites **370.11 Education for specific objectives **as an example of “special notation listed in the regular standard subdivision sequence.” That special notation does not come from Table 1; **T1—011 Systems** has a different meaning; a note at **370.11 **says “Do not use for systems; class in 370.1.” The absence of a Synthesized number components box for **370.11 **makes it clear that the number is special notation, not built with regular standard subdivisions notation. Similarly, **370.113 Vocational education **has no Synthesized number components box. Standard subdivisions may be added to build, for example: **370.1130941 Vocational education—Great Britain**.

The Introduction cites **155.9042 Stress **as an example of a subdivision of **T1—04 Special topics** that is specifically listed in the schedules. The number **155.9042 **has no Synthesized number components box; standard subdivisions may be added.

(3) If there is a Synthesized number components box, but the number was not built with standard notation from Table 1, then standard subdivisions may be added. The Introduction cites the example of geographic treatment of penal institutions being displaced from **365[.09] History, geographic treatment, biography **to** 365.9 History, geographic treatment, biography. **The number **365.973 Imprisonment—United States, . . . **has this Synthesized number components box:

(To use the WebDewey number building tool to add a standard subdivision to a built number like **365.973**, you will need to build the number from scratch, starting in this case at **365.91-365.99 Geographic treatment, biography**.)

*Note: Number spans in WebDewey never have a Synthesized number components box; but spans of numbers built with regular standard subdivisions usually have the caption “Standard subdivisions.”*

We’re pleased that the Synthesized number components box is now available to provide insight into how specific numbers are built. It’s a useful new feature for both beginners and more advanced Dewey users to better understand number building.

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