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jlvay merged 11 commits into from
Feb 2, 2026
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PALS: Base Structure & Version #152

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PALS: Base Structure & Version
ax3l Jan 7, 2026
aee82f4
Readability: Add 2 Spaces
ax3l Jan 21, 2026
2254bd1
Section: lattice -> elements
ax3l Jan 21, 2026
454270b
Update Written Standard
ax3l Jan 22, 2026
9658e1a
Simplify Wording
ax3l Jan 28, 2026
f4907fd
Clarify that lattice elements include commands
ax3l Jan 28, 2026
af3b1f2
Add `Example:`
ax3l Jan 28, 2026
da2ef1f
elements -> lattices
ax3l Jan 28, 2026
df5136f
Use magic-element-name Approach
ax3l Jan 28, 2026
431c408
fix typo
ax3l Jan 28, 2026
1dd0800
Include: Move Down
ax3l Jan 28, 2026
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54 changes: 29 additions & 25 deletions examples/fodo.pals.yaml
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Expand Up @@ -9,32 +9,36 @@
# - definition of a FODO channel that:
# - repeats a line (fodo_cell) three times
#
- drift1:
kind: Drift
length: 0.25
PALS:
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@ax3l ax3l Jan 21, 2026

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Discussed today: Start with PALS: or - PALS:?

Claude:
image

I personally also find the extra nesting to get a bit excessive if we start with a list. When we import into each other, we would anyway do it in the lattice: ... list.

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@ax3l ax3l Jan 21, 2026

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image image

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@ax3l ax3l Jan 21, 2026 •
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Discussed with @DavidSagan : We would combine files and use immediate evaluation / sets like this later on:

PALS:
  version: null  # later, we will put the version of the PALS standard here

  imports:
    - "first.pals.yaml"  # adds elements to the beginning of "lattice: ..."
    - "second.pals.yaml"  # adds more elements (to the end of) "lattice: ..."

  elements:
    # elements from first.pals.yaml
    # elements from second.pals.yaml

    - another_drift:
        kind: Drift
        length: 0.25   

    - set: "..."  # can manipulate all elements

first.pals.yaml and second.pals.yaml would use the same schema (PALS: version: elements: ...).
We can later on allow to sub-select a beamline in imports:, e.g., first.pals.yaml:FODO for a named BeamLine only.

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@ax3l ax3l Jan 28, 2026 •
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Rolled somehow back today, now includes use a "magic element name" like the set command:

Discussed with @DavidSagan : We would combine files and use immediate evaluation / sets like this later on:

PALS:
  version: null  # later, we will put the version of the PALS standard here

  lattices:
    - include: "first.pals.yaml"  # adds elements & commands
    - include: "second.pals.yaml"  # adds more elements & commands

    - another_drift:
        kind: Drift
        length: 0.25   

    - set: "..."  # can manipulate all elements

first.pals.yaml and second.pals.yaml would use the same schema (PALS: version: lattices: ...).
We can later on allow to sub-select a beamline in imports:, e.g., first.pals.yaml:FODO for a named BeamLine only.

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@ax3l ax3l Jan 28, 2026 •
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My personal preference is to call this group elements:.

I do not think it is confusing if elements includes a list of elements and commands like include/set, and it is quite descriptive (vs. writing "nodes" or "objects" or "list").

PALS:
  version: null  # later, we will put the version of the PALS standard here

  elements:
    - include: "first.pals.yaml"  # adds elements & commands

    - another_drift:
        kind: Drift
        length: 0.25   

    - set: "..."  # can manipulate all elements

    - include: "second.pals.yaml"  # adds more elements & commands

    - my_lattice:
        kind: Lattice
        branches:
          - ...

version: null # later, we will put the version of the PALS standard here

- quad1:
kind: Quadrupole
MagneticMultipoleP:
Bn1: 1.0
length: 1.0

- fodo_cell:
kind: BeamLine
line:
- drift1
- quad1
- drift2:
lattices:
- drift1:
kind: Drift
length: 0.5
- quad2:
inherit: quad1
length: 0.25

- quad1:
kind: Quadrupole
MagneticMultipoleP:
Bn1: -1.0
- drift1

- fodo_channel:
kind: BeamLine
line:
Bn1: 1.0
length: 1.0

- fodo_cell:
repeat: 3
kind: BeamLine
line:
- drift1
- quad1
- drift2:
kind: Drift
length: 0.5
- quad2:
inherit: quad1
MagneticMultipoleP:
Bn1: -1.0
- drift1

- fodo_channel:
kind: BeamLine
line:
- fodo_cell:
repeat: 3
45 changes: 39 additions & 6 deletions source/conventions.md
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Expand Up @@ -83,7 +83,26 @@ associated standards, there are packages that implement translation between latt
representational internal format defined by the package.

While the standard itself is language agnostic, this document that describes the standard
needs to use some syntax and this syntax is based upon YAML. Non-YAML syntax used here is:
needs to use some syntax and this syntax is based upon YAML.

%---------------------------------------------------------------------------------------------------
(s:palsroot)=
## PALS Root Object

The root of the PALS schema is given by this dictionary:
```{code} YAML
PALS:
version: null # version schema: defined later

lattices:
- ... # a list of lattice elements and commands
```

%---------------------------------------------------------------------------------------------------
(s:matching)=
## Matching Syntax

Non-YAML syntax used here is:

1. The {math}`N^{th}` item in a list is referred to using square brackets enclosing the index: `[N]`.
For example:
Expand Down Expand Up @@ -142,13 +161,27 @@ Optional string parameters have a default value of blank unless otherwise stated

%---------------------------------------------------------------------------------------------------
(s:includefiles)=
## Include Files
## Include Lattice Files

A lattice file can include other lattice files using an include statement.
```{code} yaml
include: <file-name>
A lattice file can include other lattices (elements and commands) using an include statement.

Example:
```{code} YAML
PALS:
# ...

lattices:
# the elements and commands of base-lattice.pals.yaml
- include: "./base-lattice.pals.yaml"

# the elements and commands of extra-lattice.pals.yaml
- include: "./base-lattice.pals.yaml"

# a list of additional lattice elements and commands
- ...
```
where `<file-name>` is the name of the file to be included.
where the include file names above are examples.
Includes simply insert the `lattices` block of the `include` file(s).

%---------------------------------------------------------------------------------------------------
(s:names)=
Expand Down