Capacity-constrained semantic strategy factorizations
Capacity-constrained semantic strategy factorizations
- 1. Purpose
- 2. Setup
- 3. Semantic hierarchies as task-dependent output partitions
- 4. Two notions of strategy recovery
- 5. Hard attribute factorizations
- 6. Relabeling obstruction
- 7. Capacity-constrained tree cuts
- 8. Top-level branches are encoded before substrategy refinements
- 9. Capacity path and “more branches are encoded”
- 10. Why an $H(Z\mid X)$ penalty alone is not enough
- 11. From weak recovery to strong recovery: semantic synchronization
- 12. Related-task graph
- 13. Alignment penalty for weakly recovered factorizations
- 14. Lexicographic and regularized objectives
- 15. Complexity as an alignment mechanism
- 16. Summary of the proposed theory
- 17. Failure modes and limitations
- 18. Relation to existing literature
- 19. Main takeaway
1. Purpose
The baseline theory shows that, for a fixed conditional law and a feasible latent factorization
the max-info criterion satisfies
Thus max-info minimizes residual generator entropy. In highly expressive classes, this becomes degenerate: if deterministic feasible generators exist, max-info selects every deterministic simulator, and the latent need not have stable semantics across inputs.
This note develops a constrained theory meant to model multi-strategy reasoning. The intended setting is:
- is a task, e.g. a theorem statement;
- is a solution, e.g. a proof;
- may be generated by one of several abstract strategies, e.g. direct proof, contradiction, induction, construction;
- the same abstract strategy has different task-specific realizations for different .
Semantic consistency means that the latent index names the same abstract branch of the task-conditioned output space across inputs.
The theory below separates three levels:
- capacity-constrained branch discovery: max-info recovers taskwise output branches;
- capacity path: increasing recovers deeper tree refinements;
- semantic synchronization: an additional cross-input simplicity/equivariance penalty aligns the branch labels globally.
2. Setup
Let be finite, with fixed input law on and fixed conditional law on .
All entropies and mutual informations are computed under the relevant induced joint law.
For a set , write
If , define the conditional law
3. Semantic hierarchies as task-dependent output partitions
Intuitively, a reasoning process can be viewed as a branching process represented as tree where each branch corresponds a strategic choice at a given level of hierarchy. We formalize this as a tree where each node of the tree is an input-dependent subset of outputs. The root node reflects all possible outputs, and each branch divides the output space into subsets reflecting different strategic choices.
A semantic hierarchy is a finite rooted tree with root , together with task-dependent branch sets
such that, for every :
- ;
- if has children , then up to -null sets.
The tree nodes are semantic objects. Their realizations may vary with .
For example, the root is “all proofs of theorem .” Its depth- children may be “direct proofs,” “proofs by contradiction,” “induction proofs,” etc. For different theorems, the actual proofs in those sets are different, but the node name is globally meaningful.
No Markov condition such as is imposed. The branch-conditioned law may depend arbitrarily on .
A tree cut of is a set of nodes such that every root-to-leaf path intersects exactly once.
Equivalently, for every input , the realized branch sets form a (task-dependent) partition of the ouptut space such that each belongs to exactly one selected branch .
Given a cut , define the branch map by letting be the unique node such that .
The associated branch random variable is
Intuitively, a cut chooses the resolution at which we describe the output. A shallow cut records a coarse strategy; a deeper cut records a more refined substrategy.
Examples and Intuition
For example, suppose for a theorem statement , proofs are organized as
and induction proofs further split as
Then a top-level cut is
This cut records only the high-level proof strategy.
A mixed-resolution cut is
This cut keeps direct and contradiction coarse, but refines induction into its two subtypes.
The set
is not a cut, because direct and contradiction proofs are not covered.
The set
is also not a cut, because a strong-induction proof lies on a path passing through both selected nodes. It would be assigned two branch labels.
The "exactly once" condition rules out both failures: every output must receive one and only one branch label.
A cut induces the factorization
whenever , with arbitrary values on zero-mass states.
Then
Thus every semantic cut gives a feasible factorization.
Preview: Why cuts matter for capacity-constrained max-info
If the latent space has size , then can represent at most an -cell cut. Maximizing
over cut-induced factorizations asks which -branch resolution captures the most information about beyond .
Since is deterministic given ,
Thus, among admissible cuts of size , max-info chooses the cut with largest conditional branch entropy.
This formalizes the idea that limited-capacity should encode the most important branching structure first, provided the strategy tree and admissibility assumptions rule out arbitrary non-semantic partitions.
4. Two notions of strategy recovery
Let denote a target strategy variable with states. In the tree model, may be the top-level depth- branch label.
A learned latent may recover in two different senses.
A factorization weakly recovers if, for every with , there exists a permutation
such that, for all positive-mass ,
This means each individual task has been decomposed into the right branches, but the latent labels may be inconsistent across tasks.
A factorization strongly recovers if there exists a single permutation
independent of such that
for all with positive mass.
Strong recovery is the semantic target: the same latent label means the same abstract strategy across inputs.
5. Hard attribute factorizations
The tree model is a special case of hard output attributes.
A hard output attribute is a deterministic map
It induces
whenever .
Intuition: concentrated
This definition relates to our discussion about potentially incorporating a term in the objective that pressures the latent variable to be concentrated given , with the intuition that a strategy is an attribute of , and in particular that a strategy is determined after observing its instantiation.
For every hard output attribute , the induced pair is a feasible factorization and satisfies
Equivalently,
^hard-attribute-identity
\begin{proof}
Feasibility follows from the law of total probability:
Because is deterministic given , . Therefore
\end{proof}
Thus, for hard branch factorizations, max-info becomes a conditional entropy maximization problem.
Let be a class of hard attributes with . Then
^hard-attribute-capacity
6. Relabeling obstruction
The following result states that the max-info objective is invariant to -dependent relabeling, obstructing the recovery of a globally-aligned strategy structure.
Let be a hard attribute. For each , let be a permutation of , and define
Then
Hence max-info alone cannot distinguish globally aligned labels from -dependent relabelings.
^x-dependent-relabeling-invariance
\begin{proof}
For each fixed , is a bijective relabeling of . Therefore
Averaging over and using #^hard-attribute-identity gives the claim.
\end{proof}
Consequently, max-info can at best recover branches up to -dependent permutation unless the model class or objective contains an additional cross-input alignment principle.
7. Capacity-constrained tree cuts
We now specialize hard attributes to tree cuts. The simplified viewpoint is:
- a cut chooses a semantic resolution;
- the cut induces the hard attribute ;
- max-info equals ;
- refining a node adds a local entropy gain;
- capacity-constrained max-info chooses the cut with maximal total gain.
When comparing a semantic cut to a learned latent variable, the cut should be viewed as an unordered partition. The same cut can be encoded by many latent variables, including variables that relabel the cut cells differently for different inputs.
Let be a cut. An internal node is split by if contains a proper descendant of .
We denote the set of nodes split by C as
Equivalently, is the set of branch decisions exposed before the tree reaches the resolution . If , then is not split; the cut stops at . If descendants of lie in , then the cut has refined below .
Let be an internal node and let . For , define
whenever . If , the corresponding contribution below is defined to be . Denote by the -dependent probability mass function over .
The split gain of is
where is the entropy of the -dependent probability distribution over .
Thus is the expected information gained by asking: conditional on lying in branch , which child of contains ? It is large when branch is reached often and its children are balanced.
Let be a cut containing an internal node . Let
be the cut obtained by replacing by its children. Then
\begin{proof}
Condition on . The branch label records which cell of the cut contains . The refined label agrees with on every branch except . On the event , it replaces the coarse label by the child of containing .
Since refines , the coarse label is a deterministic function of the refined label . Hence, by the conditional chain rule for entropy,
Rearranging terms gives
We now compute . The conditional entropy term is zero unless . Indeed, if for some , then the split did not affect that branch and deterministically.
On the event , equivalently , the refined label is the child such that . Therefore its conditional law is
Thus
where .
Combining the preceding observations,
Hence
Averaging over gives
By definition, the right-hand side is . Therefore
\end{proof}
The following result states that the information encoded by a tree-cut attribute about the output beyond the input is equal to the sum of the entropy gains from all branch decisions exposed above the cut.
For every cut ,
^cut-entropy-split-gains
\begin{proof}
The identity follows from #^hard-attribute-identity, since is deterministic given .
It remains to show
Let be the set of internal nodes lying strictly above the cut. Starting from the root cut , choose any ordering
of such that ancestors appear before descendants. Such an ordering exists because is ancestry-closed. Define cuts recursively by
Then .
By the entropy-gain lemma for splitting a node,
for each . Summing over gives
The root cut has only one possible branch label, so . Therefore
Combining this with gives
\end{proof}
The preceding decomposition turns the max-info objective for a cut into a sum of local split gains. The next result adds the capacity constraint: if may represent at most branch labels, then max-info selects the cut whose exposed branch decisions have the largest total entropy gain subject to the -cell budget. Equivalently, capacity-constrained max-info over tree cuts is a tree-structured, precedence-constrained gain maximization problem.
Let be the set of tree cuts with . For each cut , let be its branch random variable and let be the set of internal nodes lying strictly above the cut. Then
Equivalently, capacity-constrained max-info chooses the cut whose exposed internal branch decisions have maximal total split gain under the leaf budget .
Moreover, if is optimal, then the branch-induced factorization
is a max-info factorization among tree-cut factorizations with at most latent states, up to relabeling of latent states. ^tree-cut-knapsack
\begin{proof}
Recall that is a deterministic property of and represents the branch of the tree containing at resolution , hence by #^hard-attribute-identity. Immediately from #^cut-entropy-split-gains we have that for each cut , the mutual information between and the latent variable is
Therefore
If maximizes the right-hand side, then it also maximizes over cuts with . The branch-induced factorization associated with is feasible because the sets partition :
It uses latent states and has latent variable . Thus it is max-info among tree-cut factorizations with at most states, up to relabeling of the latent states.
\end{proof}
The theorem can also be written in precedence-constrained form. Let range over ancestor-closed sets of internal nodes, where ancestor-closed means implies every proper ancestor of lies in . Such an is exactly the same object as for some cut . Therefore the preceding theorem is equivalent to
Equivalently, writing , the problem is
subject to
This is the same gain maximization problem, but cuts are the primary object and is only a shorthand for the nodes split by the cut. The result follows by the following simple calculation on the size of in terms of .
For every cut ,
where .
^cut-size-split-nodes
\begin{proof}
Start from the root cut, which has one cell. Splitting an internal node replaces one cell by children, increasing the number of cut cells by . To obtain , one performs exactly the splits in .
\end{proof}
This theorem gives a precise interpretation of capacity-constrained max-info in a branching model:
Max-info chooses the branch decisions with largest total entropy gain, subject to the rule that a substrategy can be encoded only after its ancestors have been encoded.
The precedence-constrained form can be viewed as a tree-structured knapsack problem. Each internal node is an item with value and cost , where . Selecting means spending additional latent states to expose the children of . The capacity constraint
says that the resulting cut uses at most latent states. Equivalently, the total extra cost beyond the root cell is at most .
The difference from ordinary knapsack is the precedence constraint:
Thus a substrategy split can be selected only after all higher-level strategy splits above it have been selected.
If is a binary tree, for every internal node, so every split has cost . Then capacity allows exactly splits, and max-info selects the highest-gain ancestry-closed set of at most internal branch decisions.
8. Top-level branches are encoded before substrategy refinements
The preceding results show that, in the tree-cut model, max-info chooses a cut by maximizing total split gain subject to a latent-state budget. We now isolate the simplest consequence of this framework: if the root split has children, then capacity is exactly enough to expose the top-level strategy branches, but not enough to refine any one of them further.
This formalizes the sense in which top-level branches are encoded before substrategy refinements. The point is not that max-info intrinsically understands semantic depth. Rather, within the admissible class of tree cuts, any non-root refinement requires first exposing the root split and then spending at least one additional latent state. Therefore, with only available latent states, the only nontrivial cut that can expose all top-level branches is the depth- cut.
Let the root have children, interpreted as the top-level strategies:
Let be the depth- cut, and let $S:=A_{C_1} $ be the corresponding top-level strategy attribute. Thus records which child of the root contains the output .
Informally, the theorem below says:
If , so the top-level strategy is not deterministic from , then among all tree-cut factorizations using at most latent states, max-info selects the top-level strategy cut . Any substrategy refinement would require at least states.
Equivalently, at capacity , max-info recovers the top-level partition
for each input . However, the latent labels may still be permuted differently for different inputs, so this is weak recovery rather than global semantic alignment.
Assume:
- the root has exactly children;
- every non-root internal node has at least two children;
- ;
- the admissible hard attributes are tree-cut attributes, with arbitrary relabelings of the cut cells allowed.
Then, among tree-cut factorizations with , the unique max-info partition is the depth- strategy cut
Thus max-info recovers the top-level strategy partition for each input , up to -dependent permutation of the latent labels.
^top-level-recovery
\begin{proof}
A cut with at most cells is either the root cut or the depth- cut , except for refinements that would exceed the budget. Indeed, splitting the root creates cells. Any further split of a non-root internal node replaces one cell by at least two children, increasing the number of cells to at least .
The root cut has entropy . The depth- cut has entropy . Therefore the depth- cut is the unique entropy-maximizing cut under the capacity . By #^hard-attribute-identity, it is also the unique max-info partition. Latent labels may still be permuted separately for each by #^x-dependent-relabeling-invariance.
\end{proof}
Under the assumptions of #^top-level-recovery, any tree-cut factorization that separates a non-root descendant branch must have .
Hence, within the tree-cut model, max-info cannot encode a substrategy before encoding the top-level strategy split.
^substrategies-after-top-level
\begin{proof}
Any non-root split requires first splitting the root, producing cells, and then replacing at least one root child by at least two descendants. This produces at least cells.
\end{proof}
If one wants nontrivial behavior for capacities , one should include a coarser semantic tree above the named strategies, e.g. first split “constructive vs. nonconstructive,” then split “nonconstructive” into contradiction, contrapositive, etc. The same theorem then applies to that coarser hierarchy.
9. Capacity path and “more branches are encoded”
The preceding theorem identifies the first strategy level. The next result describes what happens as the capacity increases.
For each capacity , let be a solution of
subject to . If is unique for each in a set of capacities , then the capacity-constrained max-info tree-cut factorization uniquely recovers for each , up to -dependent relabeling.
If, additionally, whenever with , then the recovered max-info factorizations form a nested semantic refinement path.
^capacity-path
\begin{proof}
The first statement is exactly #^tree-cut-knapsack. If , then the larger-capacity cut performs all splits of the smaller-capacity cut and possibly more. Hence refines .
\end{proof}
A more explicit sufficient condition is available for binary trees.
Suppose every internal node has two children. Then each split costs one latent state:
Assume all split gains are distinct and ancestor-dominant:
Then the optimal cut at capacity is obtained by splitting the internal nodes with largest split gains. In particular, the max-info capacity path expands nodes in decreasing order of .
^binary-ordered-gains
\begin{proof}
Because ancestor gains are larger than descendant gains, the set of the largest gains is ancestor-closed: if it contains a node, it contains every ancestor. Since all split costs are equal to one, maximizing total gain under is achieved by choosing the largest gains. The capacity-constrained tree-cut theorem then gives the result.
\end{proof}
This formalizes the intuition that a capacity-limited latent variable encodes high-level branches first when high-level splits have larger entropy gain than lower-level refinements and the admissible class respects the hierarchy.
10. Why an penalty alone is not enough
One might try to use
to prevent degeneracy. For hard attributes, this penalty does not create a new semantic preference.
If is a hard output attribute, then
Therefore:
- if 0\le\lambda<1, the maximizers are the same as ordinary max-info;
- if , all hard attributes tie at value ;
- if , the trivial constant attribute is optimal.
^entropy-penalty-hard
\begin{proof}
By #^hard-attribute-identity, . Substitution gives the result.
\end{proof}
Thus, in the hard-branch regime, the useful capacity controls are cardinality, tree-cut complexity, description length, or an explicit cross-input alignment penalty, not a bare penalty.
11. From weak recovery to strong recovery: semantic synchronization
The tree-cut results recover the right branches locally, but only up to -dependent permutation. To recover a globally meaningful latent label, we need a cross-input alignment principle.
The central idea is:
Max-info discovers local branches. Simplicity/equivariance synchronizes their labels across tasks.
12. Related-task graph
Let be a graph connecting related inputs. An edge means that branch realizations at and can be compared by some low-complexity transformation.
For top-level strategies , assume a local semantic matching cost
Intuitively, is small if the strategy- component at task can be transformed simply into the strategy- component at task .
A flexible way to define such a cost is
where:
- is a class of simple transformations between output spaces or proof representations;
- is a complexity cost;
- is a divergence or discrepancy;
- is pushforward.
Known group equivariance is the special case where contains a known transformation. For mathematical reasoning, the transformations need not be explicitly known; they can be treated as low-complexity transports implicitly favored by a shared generator.
The local costs satisfy a diagonal alignment gap on if there are numbers such that, for every edge ,
and
This says that matching the same abstract strategy across nearby inputs is strictly simpler than matching different strategies.
13. Alignment penalty for weakly recovered factorizations
Suppose a weakly recovered factorization is indexed by local permutations , so that
Define
Assume:
- the related-task graph is connected;
- the local costs satisfy the diagonal alignment gap;
- max-info has already restricted us to weakly recovered top-level branch factorizations.
Then
Equivalently, minimizing the alignment penalty over weak max-info solutions recovers the strategy labels up to a single global permutation.
^semantic-synchronization
\begin{proof}
If is constant over , then for every edge and every ,
so each summand is diagonal and .
Conversely, if , then every summand is zero. By the diagonal alignment gap,
for every edge and every . Since is connected, this equality propagates along paths, so is independent of for every . Hence globally.
\end{proof}
This is a permutation-synchronization theorem: local branch identities are aligned by enforcing cycle-consistent, low-cost correspondences across tasks.
14. Lexicographic and regularized objectives
The preceding theorem can be implemented as a lexicographic selection rule:
Equivalently, one may use a regularized objective
provided and some globally aligned weak maximizer has .
Work in the top-level tree-cut class with , under the assumptions of #^top-level-recovery and #^semantic-synchronization. Let be the alignment penalty above, extended nonnegatively to all admissible factorizations. Then every maximizer of
strongly recovers the top-level strategy variable, up to a global permutation.
^regularized-strong-recovery
\begin{proof}
By #^top-level-recovery, the max-info value in the top-level tree-cut class is achieved exactly by weakly recovered top-level factorizations, up to relabeling and null states. Among these, #^semantic-synchronization says that is minimized exactly by globally aligned permutations, and that aligned solutions have penalty .
Any non-max-info solution has strictly smaller and nonnegative penalty, so it cannot beat a globally aligned max-info solution with penalty . Any weak but non-globally-aligned max-info solution has the same information but strictly positive penalty, so it is worse for every . Therefore every regularized maximizer is globally aligned.
\end{proof}
15. Complexity as an alignment mechanism
The alignment penalty can be interpreted as generator complexity.
Suppose the aligned generator can be written as
where is a shared interpreter and is a strategy embedding.
A globally aligned factorization has description length roughly
An -dependent relabeling requires an additional input-dependent permutation table:
with complexity
Suppose that, over the weak max-info solution set, the generator complexity has the form
where
and otherwise. Then the lexicographic rule
recovers the strategy labels up to a global permutation.
^complexity-selects-alignment
\begin{proof}
The max-info step restricts to the weakly recovered solution set. On that set, minimizing is equivalent to minimizing , whose zero set consists exactly of globally constant permutations.
\end{proof}
This formalizes the idea that a simpler generator applies a given “the same way” across inputs, while inconsistent semantics require extra machinery to implement task-dependent relabelings.
16. Summary of the proposed theory
The extension decomposes strategy recovery into three logically separate mechanisms.
16.1. Local branch discovery
Under a hard semantic hierarchy, every tree cut induces a feasible factorization. For such factorizations,
Thus capacity-constrained max-info selects the branch partition with maximal conditional branch entropy.
16.2. Hierarchical capacity path
For a semantic tree, each internal node has a split gain
where on positive-mass branches. For every cut ,
Thus max-info with latent states chooses the cut with whose split nodes have maximal total gain. This gives a precise sense in which increasing capacity encodes more branches.
16.3. Global semantic alignment
Max-info alone is invariant under -dependent relabeling. Therefore it gives at most weak recovery. To obtain strong recovery, add an alignment or complexity penalty. If same-strategy components are easier to align across related tasks than different-strategy components, then minimizing the alignment penalty synchronizes the local labels and recovers strategies up to a global permutation.
17. Failure modes and limitations
-
Capacity alone is insufficient without an admissible hierarchy.
If arbitrary partitions of are allowed, max-info may choose mass-balanced or low-level attributes rather than semantic strategies. -
Top-level branches are not automatically information-dominant.
A stylistic or local attribute can have higher conditional entropy than a reasoning strategy. The hierarchy restriction or an entropy-gap condition is doing real work. -
Weak recovery is the most max-info can provide by itself.
The objective is invariant under -dependent relabeling, so global semantics cannot be identified from max-info alone. -
Disconnected task graph gives only componentwise alignment.
If has multiple connected components, synchronization recovers one global permutation per component. -
Indistinguishable strategies are not identifiable.
If has no diagonal gap, or if two strategies induce identical branch-conditioned distributions across all relevant tasks, no objective can distinguish them without additional side information. -
Zero-mass branches are locally unidentifiable.
If , then the realization of strategy at input cannot be inferred from .
18. Relation to existing literature
-
Max-info and Jensen–Shannon divergence.
The baseline identityuses the weighted generalized Jensen–Shannon divergence introduced by Lin.
URL: https://doi.org/10.1109/18.61115 -
Information bottleneck and hard clustering.
The hard-attribute restriction resembles a conditional version of deterministic information bottleneck / hard clustering: one searches for a limited discrete representation preserving information about a target variable.
Tishby–Pereira–Bialek: https://www.princeton.edu/~wbialek/our_papers/tishby+al_99.pdf
Strouse–Schwab deterministic IB: https://doi.org/10.1162/NECO_a_00810 -
Tree cuts and hierarchical clustering.
The split-gain decomposition is the entropy-chain-rule analogue of optimizing a hierarchical decision tree cut under a leaf budget. -
Permutation synchronization.
The semantic synchronization step is formally related to group and permutation synchronization: recovering globally consistent labels from pairwise relative correspondences.
Singer angular synchronization: https://pmc.ncbi.nlm.nih.gov/articles/PMC3003935/
Pachauri–Kondor–Singh permutation synchronization: https://papers.nips.cc/paper/4987-solving-the-multi-way-matching-problem-by-permutation-synchronization
Shen–Huang–Srebro–Sanghavi map synchronization: https://papers.nips.cc/paper/6128-normalized-spectral-map-synchronization
19. Main takeaway
A precise nondegenerate theory should not claim that max-info alone recovers semantic strategies. The sharper statement is:
and
This cleanly separates the roles of information, capacity, hierarchy, and semantic consistency.