The multilateral pool

The classical contract (ʿaqd) is bilateral: a buyer and a seller, a lender and a borrower, two partners. But much of a real economy is many-sided. A thousand ṣukūk holders. A community of takāful participants. A muḍāraba’s pool of capital-providers. The pool section is how Deducible steps past the two-party contract without abandoning the discipline that governs it.

The shape

A pool declares a set of named participants, each with a share in basis points:

pool {
  holderA: 5000 bps;
  holderB: 3000 bps;
  holderC: 2000 bps;
}

The engine enforces two invariants over it (check_pool, sema.rs):

Code	Rule
POOL-1	the participants’ shares must total exactly 10000 bps (the whole).
POOL-2	there must be at least two participants. A pool of one is a bilateral contract.

The citation is plain: a multilateral participant pool, whose shares must total the whole (10000 bps), with at least two of them [scholar-verify].

What it lowers to

Codegen reduces a pool to two parallel on-chain arrays and a constructor guard:

address[] public holders;     // the participants
uint16[]  public sharesBps;   // their shares, parallel to holders

constructor(address[] memory h, uint16[] memory s) {
    uint256 sum;
    for (uint256 i = 0; i < s.length; i++) sum += s[i];
    require(sum == 10000, "POOL-1: shares must total 10000 bps");
    require(h.length >= 2, "POOL-2: a pool needs >= 2 participants");
    holders = h; sharesBps = s;
}

Distribution is a pro-rata loop over those arrays. It is the very same arithmetic the farāʾiḍ engine uses to apportion an estate by the fixed Qurʾānic shares (faraid.rs). The structure that divides an inheritance and the structure that pays ṣukūk holders are, mechanically, one.

Where it is used

Class	The pool is…
sukuk	the certificate holders (undivided ownership shares).
takaful	the participants who donate into the mutual fund.
mudarabah_pool	the rabb al-māl pool that provides the capital.

Why it matters

This is the load-bearing primitive behind the move described in the fourth paper, beyond the bilateral contract. Once “a party” can be “a pool,” the same compliance-by-construction guarantees that held for two parties hold for a crowd. The shares still sum to the whole, the loss still follows the capital, and no participant is quietly guaranteed whole. For the full grammar of the pool section, see Grammar & AST.