The problem

If you manage two or more Johnny.Decimal systems, you need a way to identify them. For example, you have a system at home and at work.

The two systems have nothing in common. But they both contain the ID 11.11. When you use this ID, to which system are you referring? It is now ambiguous.

The solution

We recognise that these two (or more) systems are distinct and separate, and assign each of them a 'system identifier' before AC.ID.

Use three characters of the form [A-Z][0-9][0-9], i.e. A00 … Z99. We refer to this as SYS.AC.ID.

Example

We assign our home system the identifier H01 and our work system W01.^* The full ID for 11.11 in each of these systems is now H01.11.11 and W01.11.11, respectively.

^*I encourage you to be more creative. Interesting letter/number combinations will help your brain.

What am I extending/gaining?

This scheme extends the number of available systems from one (1) -- the classic AC.ID -- to 2,600.

How does this affect my IDs?

Within each system, IDs are unaffected. Each system is a standard implementation of Johnny.Decimal.

How does this affect my JDex?

If your JDex contains entries for both systems, each entry must include the full SYS.AC.ID identifier. Otherwise, searching for 11.11 might return both results, which is ambiguous.

If your systems exist in separate domains, you may not need to do this. See the guidelines.

Can I use this with expand an area?

Yes. You may expand an area of a SYS.AC.ID system.

Can I use this with extend the end?

Yes. You can extend the end of a SYS.AC.ID system.

When should I use/not use this?

Use this when you have two or more systems in the same domain. Or you may choose to label systems in separate domains for clarity -- like in our home/work example.

Avoid creating multiple systems where possible -- always prefer to 'fill up' an existing system. More systems equals more complexity. Complexity is to be avoided.

Most people can fit their entire personal life in one Johnny.Decimal system. If you've run out of room, try to compress your system before creating another.