Equation 3 · Part 1 · Retrieval Is an Evidence System, Not a Memory
Symbol Z_k
What this part means
is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.
Its job in the formula
is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.
Full expression→Symbol Z_k→Article meaning
The passage around this formula
The retrieval literature said the opposite. Lewis and colleagues introduced RAG explicitly as a combination of parametric and non-parametric memory, and the architectural point is that the second is a different kind of object, not an extension of the first [ 1 ] . Their formulation treats the retrieved passage as a latent variable to be marginalised over. Writing x for the query, y for the output, and for the top k passages returned by a retriever with parameters :
Learn the underlying idea
A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.
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Sources cited in the surrounding passage
These citations provide research context; check each source for the exact claim it supports.