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Brief on lsFusion elements for AI agents

Format: very concise, for understanding and code generation. Detailed description and syntax is retrieved with tools via RAG in docs.

Core elements (from simpler to more complex)

Classes

  • Analogy: OOP classes, with multiple dispatch by parameter classes. Define object types; used in signatures of properties/actions/forms.
  • Description: base element — set of objects. Inheritance. Built-in vs user classes. Polymorphism via inheritance, ABSTRACT + += / ACTION+, MULTI.
  • Syntax (search): CLASS ClassName ['Caption'] [: ParentClass];

Properties

  • Analogy: math / pure functions. Compute facts, no state change. Declarative, close to SQL.
  • Description: DATA (stored) vs calculated (formulas, aggregates, compositions).
  • Syntax (search): name 'Caption' = DATA Type (Class1, ...); or name (Params...) = Expression;

Actions

  • Analogy: procedures / methods. Change state (DB or external). Imperative, close to Java.
  • Description: dual to properties: properties = what; actions = how it evolves.
  • Syntax (search): actionName 'Caption' (Params...) { ActionOperators }

Forms

  • Analogy: SQL query but broader (many tables at once). Universal data/UI element.
  • Description: OBJECTS (groups), PROPERTIES (what to show / actions), FILTERS (row filter). Views: interactive (SHOW), print (PRINT), structured (EXPORT/IMPORT). Extensible via EXTEND FORM.
  • Syntax (search): FORM FormName 'Caption' OBJECTS ... PROPERTIES ... FILTERS ... ;

Events

  • Analogy: DB triggers but broader. Time-dependent reactions to data changes.
  • Description: main operator WHEN; session-change analyzers CHANGED, SET, DROPPED, PREV, etc. Form events: ON CHANGE/ON EDIT/ON CONTEXTMENU/ON GROUPCHANGE/ON CHANGEWYS. Block events: BEFORE / AFTER.
  • Syntax (search): prop(...) <- Expr WHEN CHANGED(...); or PROPERTIES(...) prop ON CHANGE action(...);

Constraints

  • Analogy: integrity constraints, time-independent invariants.
  • Description: checked on APPLY; types: general (CONSTRAINT), simple (=>, NONULL, uniqueness via GROUP AGGR).
  • Syntax (search): CONSTRAINT name 'Caption' CHECK condition(...); or premise(...) => consequence(...) [RESOLVE LEFT|RIGHT];

Aggregations

  • Analogy: aggregate objects maintained declaratively.
  • Description: created via AGGR (see property operators). Platform maintains aggregate objects by rules.
  • Syntax (search): see AGGR operator below.

Additional elements

  • Navigator (NAVIGATOR): menu / routing binding forms and actions.
  • Windows (WINDOW): layout of multiple forms/areas.
  • Tables (TABLE): explicit DB tables (rare; low-level IN/integration).
  • Indexes (INDEX): explicit DB indexes (mostly auto-generated).

Modules

  • Analogy: package / assembly (.lsf file).
  • Description: unit of reuse; contains classes/properties/actions/forms/events/constraints; dependencies via REQUIRE.
  • Syntax (search): MODULE ModuleName; REQUIRE ModuleA, ModuleB;

Property operators

Basic expressions

  • Description: arithmetic, logic, strings, comparisons, type tests (IS/AS), conditional (IF ... ELSE, postfix f(a) IF g(a)).
  • Syntax (search): standard expression operators.

Composition

  • Analogy: function call inside function / function composition in math. Using one property in another's expression.
  • Description: property-from-property. Usually implicit (simple property substitution in expression).
  • Syntax (search): using properties in other properties' expressions.

Grouping (GROUP)

  • Description: value aggregates (sum/count/max/min/last/concat). Not object aggregates.
  • Syntax (search): GROUP SUM source(...) IF Condition; or GROUP SUM source(...) BY groupExprs...;

Partition / window (PARTITION)

  • Description: window logic: ranks, previous value, cumulative.
  • Syntax (search): PARTITION AggOp expression IF Condition ORDER orderExprs...;

Aggregating objects (GROUP AGGR)

  • Description: maintains aggregate objects via BY.
  • Syntax (search): GROUP AGGR Class x WHERE BaseCondition BY groupExprs...;

Operator AGGR

  • Description: creates/maintains aggregate objects automatically.
  • BNF: aggrPropertyDefinition ::= AGGR baseEventPE customClassUsage WHERE propertyExpression (NEW baseEventNotPE)? (DELETE baseEventNotPE)?
  • Syntax (search): AGGR Class x WHERE condition(...) [NEW newEvent] [DELETE deleteEvent] [MATERIALIZED] [INDEXED];

OVERRIDE

  • Description: merge multiple sources with priority.
  • Syntax (search): OVERRIDE expr1, expr2, expr3;

RECURSION

  • Description: recursive properties (trees/graphs/closures).
  • Syntax (search): RECURSION baseExpr THEN stepExpr;

ABSTRACT

  • Description: declare abstract property; implementations via += in other modules.
  • Syntax (search): ABSTRACT [MODIFIERS] Type (ParamClasses...); and prop[Context](Params...) += implExpr;

Action operators

Basic operators

  • Mutations: assignment (<-), NEW, DELETE.
  • Action call: Analogy — function / procedure / method call. Simply action name with parameters. Not a mutation, executes another action.
  • Syntax (search): property(...) <- Expression [WHERE ...];, NEW alias = Class { ... }, DELETE ... WHERE ...;, actionName(params...);

Sequence

  • Description: ordered block of actions.
  • Syntax (search): actionName(Params...) { op1; op2; }

FOR loop

  • Description: iterate all tuples where condition property is not NULL; can create objects.
  • Syntax (search): FOR Expression [ORDER ...] [TOP n] [OFFSET m] [NEW alias = Class] DO { ... } [ELSE { ... }]

WHILE loop

  • Description: repeat while condition property somewhere is true (not NULL).
  • Syntax (search): WHILE condition DO { ... }

Branching

  • Description: IF, CASE, MULTI (polymorphic branching).
  • Syntax (search): IF ... THEN { ... } ELSE { ... }, CASE WHEN ..., MULTI impl1[p](p), impl2[p](p);

Flow control

  • Description: BREAK, CONTINUE, RETURN, TRY...CATCH, NEWTHREAD, NEWEXECUTOR.
  • Syntax (search): standard flow keywords.

Form actions

  • Description: SHOW, DIALOG, SEEK, EXPAND, COLLAPSE.
  • Syntax (search): SHOW FormName [OBJECTS ...];, DIALOG FormName OBJECTS ... INPUT [FILTERS ...] DO { ... }, SEEK [FIRST|LAST] group = obj;

Change sessions

  • Description: isolated change set. Before APPLY, data is session-local. On APPLY: success → commit; failure → canceled() = TRUE, applyMessage() has error, data remains in session.
  • Session ops: NEWSESSION action (independent), NESTEDSESSION (dependent nested). Use for work units (dialog, import, file processing).

Form representations

Interactive view

  • Analogy: usual app pages but single execution flow (no split server/client language).
  • Description: SHOW opens interactive form; DIALOG modal with INPUT / FILTERS; DESIGN sets UI layout. INPUT — prompt user for value. Reactive updates; WYSIWYG.
  • Syntax (search): SHOW formName [OBJECTS ...] [DOCKED];, DIALOG formName OBJECTS ... INPUT [FILTERS ...] DO { ... }, DESIGN formName { ... }, INPUT var = Type DO { ... }

Print view

  • Analogy: reports (jrxml + JasperReports).
  • Description: jrxml defines print layout; report initiated from lsFusion.
  • Syntax (search): PRINT formName [OBJECTS ...] TO FILE fileVar;

Structured view

  • Analogy: structured data formats (JSON, XML, XLSX, DBF).
  • Description: EXPORT action outputs to file/stream; JSON property builds JSON; IMPORT loads back.
  • Syntax (search): EXPORT FROM expr1, expr2 TO fileVar;, prop(...) = JSON expr;, IMPORT JSON|CSV|XLS|XML FROM fileVar TO props...;

Integration

  • Idea: same property/action paradigm for external and internal systems.

From current system to external (imperative, actions)

  • Description: EXTERNAL — HTTP/external code/SQL as actions.
  • Syntax (search): EXTERNAL Name 'id' [OPTIONS] (Params...);

From current system to external (declarative, properties)

  • Description: CUSTOM UI components with JSON interface; JSON build structures for UI/API.
  • Syntax (search): OBJECTS alias = Class CUSTOM 'componentName' ..., prop(...) = JSON expr;

From external systems to current

  • Description: Action API — call lsFusion actions via HTTP. Protocol HTTP (ports 7651). Action modes: EXEC (by name), EVAL (code with action run), EVAL ACTION (action code). Form API — work with forms via HTTP for frontends. Actions marked @@api for API access.
  • Syntax (search): action option @@api, URLs /exec?action=..., /eval?script=..., /eval/action?script=...

From current system to internal (imperative)

  • Description: INTERNAL — call Java code; on Java side use findProperty, read, change.
  • Syntax (search): INTERNAL Name 'id' [OPTIONS] (Params...);

From current system to internal (declarative)

  • Description: FORMULA — properties computed by SQL.
  • Syntax (search): prop(...) = FORMULA 'sql expression with $1, $2, ...';

Physical model (DB structure)

  • Analogy: manual/dynamic DB schema control (tables, indexes, materialization).
  • Description: performance/open schema focus.
  • Syntax (search): TABLE tableName ['dbName'] (ClassOrParams...);, prop = DATA Type (Class) MATERIALIZED ['dbFieldName'] INDEXED ['indexName'];

Extensions

  • Description: modularity/polymorphism at module level: EXTEND CLASS, EXTEND FORM, ABSTRACT + +=, ACTION+.
  • Syntax (search): EXTEND CLASS ClassName : ParentClass;, EXTEND FORM FormName ... ;, prop(...) += implExpr;, ACTION actionName(...) + { ... }

Metaprogramming

  • Analogy: code generators/templates in language.
  • Description: @ operator generates code from descriptions; IDE can auto-generate.
  • Syntax (search): @metaName { ... }

Identification & ergonomics

  • Namespaces: control visible names. Syntax (search): NAMESPACE MyNamespace;
  • Explicit typing: params/local props are typed. Syntax (search): LOCAL var = Type ();
  • String interpolation: build strings from identifiers/values (also for i18n). Syntax (search): '{namespace.element}'

Internationalization

  • Description: captions via resource bundles (*ResourceBundle.properties). Use IDs like {use.case.i18n.book}; UI switches language automatically.
  • Syntax (search): CLASS Book '{use.case.i18n.book}';

Migration

  • Description: migration files describe schema/data evolution; IDE auto-generates lines on renames; safe DB evolution.

Mini map for AI

  1. CLASS → object type (table).
  2. = DATA or = expression → property.
  3. { ... } without = → action (imperative).
  4. FORM → UI/query/report definition.
  5. SHOW / DIALOG / PRINT → open/print form.
  6. EXPORT / IMPORT → external formats for properties/forms.
  7. GROUP / PARTITION → value aggregates.
  8. GROUP AGGR / AGGR → aggregate objects.
  9. NEWSESSION / APPLY / canceled() → transaction/session control.
  10. EXTEND / ABSTRACT / += / +{ → extension & polymorphism points.
  11. WHEN → data-change event; ON → form event.