# Interface: PartTag

[**lifecycle-kit**](https://jonbogaty.com/lifecycle-kit/api/readme/index.md)

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[lifecycle-kit](https://jonbogaty.com/lifecycle-kit/api/readme/index.md) / [forms](https://jonbogaty.com/lifecycle-kit/api/forms/readme/index.md) / PartTag


# Interface: PartTag {#interface-parttag}


Defined in: [forms/path.ts:173](https://github.com/jbcom/lifecycle-kit/blob/074e4e7b8038d3e2de9eb44c4b5b5aee0ef02b48/src/forms/path.ts#L173)

Which anatomical part a shape belongs to.

A flat label, not a tree. The assemblage stage has to put each part in a
depth band, cast a directional light from one part onto the parts behind it,
and give each band its own parallax offset. It cannot do any of that against
an anonymous list of outlines — it would have to GUESS where one part ends
and the next begins, and guessing wrong is precisely why the design doc says
"parts currently read as stickers rather than anatomy".

So the emitting rule, which is the only thing that actually knows, says so.
`pair` knows it just emitted a left and a right appendage; nothing
downstream can recover that from coordinates alone.

Deliberately a string and not a closed enum. A closed set would be the
catalogue failure one level down — capping the vocabulary at whatever
someone had time to name, so that a rule producing a genuinely new kind of
part has nowhere to put it. Consumers group by equality and ignore labels
they do not recognise.

`index` disambiguates repetitions of the same part: `repeat` emitting three
body segments tags them `("segment", 0..2)`, and `pair` tags a left and
right as the same part with different indices. That is what lets a depth
band be assigned per repetition — the near legs occlude the far ones.


## Properties {#properties}



### index {#index}


> `readonly` **index**: `number`

Defined in: [forms/path.ts:175](https://github.com/jbcom/lifecycle-kit/blob/074e4e7b8038d3e2de9eb44c4b5b5aee0ef02b48/src/forms/path.ts#L175)

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### part {#part}


> `readonly` **part**: `string`

Defined in: [forms/path.ts:174](https://github.com/jbcom/lifecycle-kit/blob/074e4e7b8038d3e2de9eb44c4b5b5aee0ef02b48/src/forms/path.ts#L174)