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Version: 7.0

lsFusion Brief

Brief on lsFusion elements for AI agents​

This article is the TOP of the brief branch: the model in outline, plus the map that says which article to open. It is deliberately not a short version of those articles. What is here is enough to classify a task and answer a rough conceptual question.

Which branch: language — statement / operator syntax; paradigm — concepts and the system-module libraries; how-to — task recipes. Those three are searched with lsfusion_retrieve_docs; when unsure which one, omit the filter and it searches all three and merges them.

brief and rules are not searched. Each is a small set of articles, named and delivered whole by lsfusion_get_guidance: brief says what an area offers, rules states the constraints on using it. The rules map, in the top Rules article, says when reading one of its articles becomes mandatory.

The model​

  • A class is a set of objects. It types everything else: a property or action is signed by the classes of its parameters.
  • A property computes a fact and changes nothing. It is either stored (DATA) or calculated from an expression.
  • An action changes state. Properties say what is true; actions say how it evolves.
  • A form describes objects and the properties shown for them, and the same description serves the interactive view, the printed one and the structured one.
  • Changes do not reach the database as they are made. They collect in a change session until APPLY writes them or CANCEL drops them.
  • A project is composed of modules; how data is stored and made fast is the physical model, and exchange with anything outside is integration.

Two misreadings worth pre-empting, because everything downstream depends on them:

  • A class does not map to a table. A table holds property values; its key fields hold object ids and are typed by the parameter classes of those properties.
  • The system modules are a library of ordinary properties and actions, not built-in language operators. Only System is implicit; the rest need REQUIRE before their declarations are reachable.

The brief articles — which one to open​

Four articles, read whole with lsfusion_get_guidance(brief='<name>'). Match on either column: the intent describes the task in the user's terms, the anchors are what the code looks like.

nameopen it when the task is tolanguage anchors
logiccompute, store, change, aggregate, constrain or react to dataCLASS, DATA, =, GROUP, PARTITION, AGGR, <-, NEW, FOR, WHILE, WHEN, <- WHEN, CONSTRAINT, NEWSESSION, APPLY
viewshow data to a person — a form, its layout, a menu, a report — or localize what they readFORM, OBJECTS, PROPERTIES, FILTERS, SHOW, DIALOG, DESIGN, PRINT, NAVIGATOR, WINDOW, {id} captions
physicalcontrol storage or speed, organize modules, extend or generate declarations, or rename something that already existsTABLE, MATERIALIZED, INDEX, MODULE, REQUIRE, NAMESPACE, EXTEND, META, @, migration.script
integrationmove data in or out, or let another system call inIMPORT, EXPORT, JSON FROM, EXTERNAL, INTERNAL, FORMULA, HTTP endpoints

Where they overlap — read both:

  • a form event (ON inside a FORM) is logic for what it does and view for where it lives;
  • import or export of a FORM is integration for the exchange and view for the form it goes through;
  • a MATERIALIZED property is logic for what it computes and physical for what that costs;
  • extending an element is physical for the mechanism and the area of the extended element for the meaning.

Running the result — launch settings, the user interface, the security policy, the scheduler, backups, monitoring, logs, the profiler — has no brief article. Search the paradigm branch for it.

Mini map for AI​

  1. CLASS → object type (a set of objects).
  2. = DATA or = expression → property.
  3. { ... } without = → action (imperative).
  4. FORM → UI / query / report definition.
  5. SHOW / DIALOG / PRINT → open or print a form.
  6. EXPORT / IMPORT → external formats for properties and forms.
  7. GROUP / PARTITION → value aggregates.
  8. GROUP AGGR / AGGR → aggregated objects.
  9. NEWSESSION / APPLY / canceled() → session control.
  10. EXTEND / ABSTRACT / += / +{ → extension and polymorphism points.
  11. WHEN, <- WHEN → events on a data change; ON inside a FORM → a form event.
  12. Utils / Time / System / Authentication → system modules; string, number and date functions, currentUser, currentDate live there.