Conceptual Art pioneer Lawrence Weiner has vastly extended and rewritten the notion of sculpture--language is his medium, and his sculpture is text. In Weiner's mind, it is of no importance whether or not a work is ''realized''--it is entirely up to the ''reader'' of a work of art whether and how she will implement the work in her own head. Beyond this, a work can be ''realized'' in many forms--since 1968, Weiner has been publishing his language-oriented...