Demo

The sources' own worked example, run by a reference engine. Not a product.

What you are looking at

Every business application tracks objects through a lifecycle: a customer is signed up, then verified, then active. Almost every system does that with a status column somebody's code has to keep right.

PMDA does it the other way round. An object's State is computed from its data, by rule: an Artist with a createdDate is a Created Artist, one with an activatedDate is Active. Nothing is stored, so nothing goes stale. And every change to an object passes through one gate declared in the model: a Filter says when an Operation is offered, Derivations fill in values, Conditions say what the result must satisfy.

This page runs the sources' own worked example against a small engine that implements exactly what the specification currently says. Pick a scenario, then change anything and watch both panels recompute.

Why it matters

One model decides, not scattered code.: What is allowed, what is required and what is filled in are all declared next to the object they govern. Change the model and the application follows. shown below
Status is never stale.: There is no status column to migrate or reconcile; an object is whatever its data says it is. shown below
Every refusal names its rule.: A rejected change carries the Condition that rejected it, in the message the model author wrote. shown below
Replayable, deterministic behaviour.: The method's headline claim. Not yet provable as written: the sources leave one rule undefined and two formulas read the clock. Both are on this page. open, Q-G-0001, Q-G-0034

Pick a scenario

Each one sets the data, the Operation and the Authorization, then runs. Everything below stays editable afterwards; the moment you change something it is your scenario.

State is computed, never stored

The engine holds no status field. It reads the object's data against each State's restriction and reports every State that holds. Edit the data on the right and the set on the left recomputes.

Object

computing…

Its data

The names and dates are the demo's own; no source gives instance data. Only the model is Guil's.

Relations Artist#1 hasUser User#1 Artist#1 isAuthorOf Artefact#1

Every transition passes through the same gate

An Operation is a request to move an object to a State. The gate below is the method's answer, step by step. Click a step to read what it checked.

Operation Authorization now supplied, never the wall clock acting user supplied, never the environment

No transcribed table pairs an Operation with the State it achieves; the pairing in the Operation list is read off the sources' naming convention (Create → Created, Instantiate → New, Activate → Active). Q-G-0041.

What the sources leave open

A reference implementation surfaces what prose hides. Four things this page shows that the blog and the patent do not settle:

Which State an object is in when several restrictions hold. The State panel shows the set; the repair previews show the two candidate rules. Q-G-0001.
Whether the example can be replayed. Both worked Derivation formulas read the clock or the acting user, so the demo makes you supply them. Q-G-0034.
Five Conditions that attach to nothing. The source spells their State "Create Artist" and "CreatedUser"; no State has either name. Read those spellings as the nearest defined State Q-G-0042.
Five Conditions that cannot be evaluated. Their "enforces property" cell holds a State name instead. Q-G-0040.

The model, as transcribed

Show the four tables the engine runs against

Parsed from the three figure transcripts, not retyped. Every row links to the cell it was read from; a row marked UNCERTAIN is a cell the transcript itself could not read with confidence, and one marked RECONSTRUCTED is our extrapolation, not a source.

Verification status of the three source transcripts: conditions-validates-state (unverified), derivation-garantees-states (unverified), filter-and-operations (unverified). No human has re-read the source images against any of the transcribed text below. An UNCERTAIN mark is the transcriber's own flag, raised at transcription time — it is not the product of a review. The absence of a mark is not verification. An unmarked row has not been checked any more than a marked one; it simply was not flagged as uncertain by whoever transcribed it. See /evidence for the verification ladder in full.

States

Name	Thing	Restrictions	Source
New Artist	Artist	has no createdDate	BLG:business-capability-definition-using-pciml-in-detail
Created Artist	Artist	has createdDate	BLG:business-capability-definition-using-pciml-in-detail
Active Artist	Artist	has activatedDate	BLG:business-capability-definition-using-pciml-in-detail
New User	User	has no createdDate	RECONSTRUCTED — not in any source
Created User	User	has createdDate	RECONSTRUCTED — not in any source
New Artefact	Artefact	has no createdDate	RECONSTRUCTED — not in any source
Created Artefact	Artefact	has createdDate	RECONSTRUCTED — not in any source

Filters

ID	Operation	Subject	Predicate	Object	Source
Filter 1	Create Artist	—	—	New Artist	IMG:filter-and-operations#r3
Filter 2	Instantiate User	—	—	Created Artist	IMG:filter-and-operations#r4
Filter 3	Create User	Created Artist	hasUser	New User	IMG:filter-and-operations#r5
Filter 4	Activate Artist	Created Artist	hasUser	Created User	IMG:filter-and-operations#r6
Filter 5	Instantiate Artefact	—	—	Active Artist	IMG:filter-and-operations#r7
Filter 6	Create Artefact	Active Artist	isAuthorOf	New Artefact	IMG:filter-and-operations#r8
Filter 7	Publish Artefact	Active Artist	isAuthorOf	Created Artefact	IMG:filter-and-operations#r9

Conditions

Name	Target State	Type	Enforces	Source
New Artist requires artistID	New Artist	Error	artistID	IMG:conditions-validates-state#r3
Created Artist requires firstName	Create Artistno State of this name — nearest "Created Artist". Q-G-0042	Error	firstName	IMG:conditions-validates-state#r4 UNCERTAIN
Created Artist requires lastName	Create Artistno State of this name — nearest "Created Artist". Q-G-0042	Error	lastName	IMG:conditions-validates-state#r5 UNCERTAIN
Created Artist requires artisticName	Create Artistno State of this name — nearest "Created Artist". Q-G-0042	Error	artisticName	IMG:conditions-validates-state#r6 UNCERTAIN
Active Artist requires hasUser	Active Artist	Error	hasUser	IMG:conditions-validates-state#r7
Created User requires userName	CreatedUserno State of this name — nearest "Created User". Q-G-0042	Error	userName	IMG:conditions-validates-state#r8 UNCERTAIN
Created User requires password	CreatedUserno State of this name — nearest "Created User". Q-G-0042	Error	password	IMG:conditions-validates-state#r9 UNCERTAIN
New Artefact requires artefactID	New Artefact	Error	New Artefactnames a State, not a property — unevaluable, Q-G-0040	IMG:conditions-validates-state#r10 UNCERTAIN
CreatedArtefact requires hasPhoto	Created Artefact	Error	Created Artefactnames a State, not a property — unevaluable, Q-G-0040	IMG:conditions-validates-state#r11 UNCERTAIN
CreatedArtefact requires isTaggedWith	Created Artefact	Warning	Created Artefactnames a State, not a property — unevaluable, Q-G-0040	IMG:conditions-validates-state#r12 UNCERTAIN
CreatedArtefact requires artefactName	Created Artefact	Error	Created Artefactnames a State, not a property — unevaluable, Q-G-0040	IMG:conditions-validates-state#r13 UNCERTAIN
CreatedArtefact requires artefactDescription	Created Artefact	Error	Created Artefactnames a State, not a property — unevaluable, Q-G-0040	IMG:conditions-validates-state#r14 UNCERTAIN

Derivations

Name	Target State	Formula	Writes	Enforced On	Source
CreatedDate Default Value	Created Artefact	afn:now() ambient — breaks replay, Q-G-0034	createdDate	ArtistandArtefactPublishingAuthorization	IMG:derivation-garantees-states#r3 UNCERTAIN
CreatedBy Default Value	Created Artefact	pmda:User() ambient — breaks replay, Q-G-0034	createdBy	ArtistandArtefactPublishingAuthorization	IMG:derivation-garantees-states#r4 UNCERTAIN