Nevertheless, several SMILES software implementations have been released. Each one represents a unique set of decisions about how to reduce the published broad SMILES descriptions to a specification detailed enough for software development. Some implementations have themselves been reverse-engineered for clues. The Daylight implementation in particular is sometimes considered a de facto SMILES specification. Unfortunately, access to this implementation is restricted by commercial licensing, as is the case with several SMILES implementations. Moreover, reverse engineering is unlikely to address every question because of the vast search space defined by SMILES. Although some implementations are released under Open Source licenses, they are neither authoritative nor unanimous in their interpretations.