The problem

There are situations where almost everything fits in a standard Johnny.Decimal system. But a few items either break the 'no more than 100 IDs' rule, or need to be repeated in some way.

These are minor extensions to your system that don't require the more complex expand an area solution.

Examples

Your kids: you're using the standard life admin pack and you have four kids. The ID 11.24 Eyes, ears, & teeth -- which covers things like eye checks, glasses, dental checks, braces, and hearing tests -- is quite busy. You want a way to track each child's visits and documents.

A repeated task within a larger project: we had to install cabling in 13 data centres. But there was already a complete ID allocated to cabling: 72.02. I could have used a new ID for each data centre. But this didn't match the system's overall pattern and it wouldn't have been memorable. Plus I wanted a unique reference for each data centre's cabling for things like our project schedule.

My blog: this site's blog posts will number more than 100. But I want each to have a unique ID.

The solution

Add a final identifier after the ID, and separate them with a +. Ideally a simple sequence or code that represents the thing being extended. We call this the sub-ID, and refer to it as AC.ID+SUB.

Examples

Your kids: in our JDex, we add initials or a short code to represent each child. So 11.24+JEM is a note for anything to do with Jemima's visits to the optician or dentist. Similarly, we have 11.24+BEL, 11.24+MAR, and 11.24+WEN for Belinda, Marie, and Wendy.

A repeated task within a larger project: to create IDs for each of the 13 data centres, I used an existing code for that location. The final IDs looked like 72.02+X01, where X01 was a particular data centre.

My blog: for each post, I begin with the category ID: 22.00. Then append a sequential four-digit post ID. This creates the range 22.00+0000 … 22.00+9999.^* Four digits allows for 10,000 posts. Three digits would not have been enough.

^*The blog currently uses a decimal as the final separator, not a plus. I am in the process of updating it.

What am I extending/gaining?

This scheme extends specific IDs or categories by an arbitrary number of sub-IDs.

How does this affect my IDs?

Your IDs are extended at the end.

How does this affect my JDex?

You may choose to record these sub-IDs in your JDex. But it might not be necessary. See the guidelines.

Can I use this with multiple systems?

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

Can I use this with expand an area?

No. For an expanded area, extending the end no longer makes sense because you're not using standard AC.ID.

When should I use/not use this?

You should use this in limited situations, in specific categories or IDs.

If you find yourself extending the end too frequently within a system, question its design. You might need to split it into multiple systems. Or you might need to expand an area of the system.