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# sisudoc-ocda-lib
The **object-centric document abstraction as a library**: the model, and
loaders for both of the forms it is written in.
Written by Claude (Anthropic), working in Claude Code from the specification,
at the direction of and reviewed by Ralph Amissah.
**One reader per language, in a directory named for the language.**
| | |
|--------------------|---------|
| [`dlang/`](dlang/) | D |
| [`gleam/`](gleam/) | Gleam |
| `ruby/` | to come |
## What it is for
The readers in `sisudoc-ssp-reader` and `sisudoc-ocda-db-reader` each read
one serialisation and print. A **writer** needs neither: it needs the document.
```
.ssp ─┐
├─> the model ─> a writer
.ocda.db ─┘
```
So this library holds the model and both loaders, and **a writer cannot
tell which serialisation it was handed** - exactly as spine's own writers
cannot, since spine 0.25.0.
That is the whole of the idea. The readers become thin programs over this,
and the writers are functions from the model to bytes.
## The checks that matter
The claim above is only true if the loaders agree, so the library asks. Two
programs, in each language:
```sh
ocda-agree <doc>.ssp <doc>.ocda.db [lang] # do the two loaders agree?
ocda-dump <file>.ssp|<file>.ocda.db [lang] # the whole model, canonically
```
`agree` compares two models within one language. **`dump` is the stronger
of the two**, and the reason it exists: it writes the entire loaded model
out in a fully determined form, and the D and the Gleam library write it
*byte for byte alike*. So four questions can be asked, all of them with
`diff`:
| | |
|-----------------------------|---------------------------------|
| D: `.ssp` == `.ocda.db` | **36 of 36** document-languages |
| Gleam: `.ssp` == `.ocda.db` | **36 of 36** |
| `.ssp`: D == Gleam | **36 of 36** |
| `.ocda.db`: D == Gleam | **36 of 36** |
None of those held at first.
## What the checks found
### the ten-field check: a blank first text line
An object whose **first text line is blank** lost it. The loader decided
whether to start a new line by asking whether the accumulated text was
empty, which is not the same question as whether a line has been seen. Of
the sample collection **seven documents have verse opening on a blank
line**, and in every one of them the blank was dropped. Eight of
thirty-six documents disagreed.
Nothing else had caught it. The two `.ssp` readers had been compared on
*section counts*, which this does not change. It took loading the same
document two ways and comparing the objects.
Fixed here and in `sisudoc-ssp-reader/dlang`, which carried the same code.
### the whole-model dump: four more
The ten-field check was enough for that and not enough for anything
subtler. Dumping the whole model found four further disagreements between
the two loaders:
1. **`.identifier` and `.anchor`.** The `.ssp` emits a property only when it
carries information, so the identifier is absent when it is simply the
ocn and the anchor is absent when it is the segment name; the database
stores both unconditionally. Over one document that is **1,314
identifiers and 69 anchors**. The loaders now derive them, which is what
the model means.
2. **`make` and `doc_has`.** The database has one metadata table where the
text form has three blocks, and tells them apart by a key prefix. The
loaders unprefix them, so a writer asks `make["footer"]` whichever
serialisation it was handed.
3. **The JSON columns were scanned rather than parsed.** Phobos writes `/`
as `\/`, so every heading containing a slash came back with a backslash
in it: **all 36 document-languages** differed on
`heading_ancestors_text` and nothing else had shown it.
4. **`translation.ocn_aligned`** is in the database and cannot be in a
`.ssp`, which is one language and cannot know whether the languages
share a numbering. It is a fact about the *file*, so the loaders leave
it out rather than letting a writer tell which serialisation it was
given.
The first three are defects. The fourth is a real asymmetry between the two
serialisations, and naming it is the useful part.
## What it reads, and what it does not
| | | |
|-----------------------|------------------------------------------------------------------|-------------------|
| `.ssp` | yes | |
| `.ocda.db` | yes, any language of it | |
| `.sisupod` | yes, any language it carries | D only, see below |
| `.zip` pod | yes, any language it carries | |
| `.sst`, `.ssm` markup | **no, and not planned**: that is a parser, which is spine's work | |
| a url | no | |
A pod carries the abstraction only when spine was asked for it: `--pod2`
puts it in, `--source` does not. A pod without one is refused with a message
saying which flag makes a pod this library can read, because that is a fact
about the pod rather than about the library.
**Over the reference collection, a `.sisupod` gives the same model as the
`.ssp` beside it: 36 of 36 document-languages, byte identical dumps.** A
writer over the library therefore gained a third input form without being
touched, which is the point of the dispatch being in one place.
### the one thing the Gleam library cannot do
A `.sisupod` is **one zstd frame wrapping** the zip. The D library reads both
through a declared `libzstd`. The Gleam library reads the **zip and not the
frame**, because the only zstd on the BEAM is a NIF that clones zstd from
github in its own build and so cannot be built in a sandbox without patching
it.
So a `.zip` pod is read in both languages, a `.sisupod` in D only, and the
Gleam refusal says why and says `zstd -d` rather than claiming the file is
malformed. It is a packaging limit, not anything about the format, and it is
the only place the two libraries differ in what they accept.
`ocda/load` is the one place in each language that decides what a path is,
so a new input form is added once and every reader and writer gains it.
## The format
Specified in **sisudoc-abstraction-format**: `ocda-model.md` for the model
this library implements, and the two format specifications for the loaders.
Section 4 of `ocda-db-format-specification.md` gives the column by column
correspondence the `load_db` of each language follows.
At format **2.x**.
|
