Stackless Processing of Streamed Trees

Corentin Barloy (1) , Filip Murlak (2) , Charles Paperman (1)

1 LINKS - Linking Dynamic Data
2 UW - University of Warsaw

Processing tree-structured data in the streaming model is a challenge: capturing regular properties of streamed trees by means of a stack is costly in memory, but falling back to finite-state automata drastically limits the computational power. We propose an intermediate stackless model based on register automata equipped with a single counter, used to maintain the current depth in the tree. We explore the power of this model to validate and query streamed trees. Our main result is an effective characterization of regular path queries (RPQs) that can be evaluated stacklessly-with and without registers. In particular, we confirm the conjectured characterization of tree languages defined by DTDs that are recognizable without registers, by Segoufin and Vianu (2002), in the special case of tree languages defined by means of an RPQ.

Mots clés: weak validation; automata; JSON; XML; querying; streaming; phrases streaming

Domaines: Base de données [cs.DB]; Théorie et langage formel [cs.FL]; Traitement du texte et du document; Logique en informatique [cs.LO]

Corentin Barloy, Filip Murlak, Charles Paperman. Stackless Processing of Streamed Trees. PODS 2021 - Symposium on Principles of Database Systems, Jun 2021, Xi'an, Shaanx, China. ⟨10.4230/LIPIcs⟩. ⟨hal-03021960⟩