Locator Algebra (3)

• Dependent-Join:

  • d-join[f]: L ? L, where f: PL ? Ld-join[f](x) = ?u ? x concat(prefix(u),f(tail(u))
  • Example: return all titles of books in their book contextselect[“title”](d-join[children(.)] (select[“book”](d-join[return(children(.))](x)) =/book?/title

• Kleene Star:

  • fixpoint-operator for recursive descent queries
  • *[f]: L ? L, where f: L ? L*[f](x) = f(x) ? *[f](f(x))
  • Example: select all titles in their original contextselect[“title”](d-join[children(.)] (*[d-join[return(children(.)](.))](x))=//*?/title
  • maybe too general for physical algebra

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