Language Reference

Facts are loaded from external systems (see the mental model); .tln files contain blocks that reason over them.

Values

42            3.14                 // numbers
"outpatient"                       // strings — always double-quoted
true          false                // booleans
7 days   30 days   12 months   1 year   // durations
["health", "cancellation"]   [100, 200]  // lists

Operators

>  <  >=  <=  ==  !=  ~=        // comparison
+  -  *  /  %                   // arithmetic
and  or  not                   // logical
in [ … ]      not in [ … ]      // membership
contains   starts_with   ends_with   older_than   newer_than   // string / temporal

Selectors

A selector picks which records a block runs over:

for records where type == "product"
  and category == "van"
  and attr "price" > 100
  and status == "active"
  and is "high_value"          // reference a define

Core blocks

define — reusable conditions

define "high_value" {
  attr "amount_chf" > 10000
}

rule — enforce a constraint (allow / block)

rule "Reject blacklisted provider" {
  for records where type == "claim"
    and attr "provider_status" == "blacklisted"
  block "approve_claim"
  reason "Provider {attr.provider_id} is on the fraud blacklist"
}

Swap block for allow to auto-approve. Higher priority wins conflicts; a strict rule is non-negotiable and an overrides "Other rule" rule defeats a named one.

detect — find patterns and flag them

detect "Over the per-visit cap" {
  for records where type == "claim"
    and attr "amount_chf" > attr "per_visit_cap"
  flag matching items
  label "Claim {item.id}: {attr.amount_chf} CHF over cap"
}

recommend — suggest the next step

recommend "Schedule reviewer" {
  when detect "Over the per-visit cap" matches
  suggest "Route claim {item.id} to a senior adjuster"
}

combine — optimal combinations

combine "Reorder picks" {
  for records where type == "stock_item" and status == "active"
  select 3 from records
  minimize total(attr "reorder_cost")
  subject_to total(attr "reorder_cost") <= 5000
  return id, reorder_cost
}

combine runs real multi-objective optimization (Pareto / genetic / ant-colony / ILP backends); add more minimize / maximize objectives and subject_to constraints as needed.

Templates

label, reason, and suggest strings interpolate {…}:

{attr.<name>}          a record's attribute        {item.name}   the matched item
{count}                number of matches            {item.id}     the matched id
{total(attr.<name>)}   sum over matches             {avg(attr.<name>)}
{days_until(<date>)}   days until a date            {days_since(<date>)}

Priorities

CRITICAL   immediate action        HIGH   within days
MEDIUM     within weeks            LOW    informational

Metaprogramming — compile-time macros

Tln has compile-time macros built into core — defmacro / quote / unquote, Elixir-style — that generate rules before validation, so boilerplate disappears while the runtime stays pure and deterministic. See Metaprogramming for the full worked example and a side-by-side with Prolog’s term_expansion.

Priorities and beyond

Beyond these core blocks, Tln adds ML (predict, forecast, classify, cluster, find), MCP orchestration (workflow, on, collect, enrich), reactive on change blocks, and integrity constraints — all in Beyond Prolog.