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\section{library(uuid): Universally Unique Identifier (UUID) Library}

\label{sec:uuid}

\begin{tags}
\mtag{See also}- \url{http://www.ossp.org/pkg/lib/uuid/} \\- \url{https://en.wikipedia.org/wiki/Universally_unique_identifier}
    \tag{To be done}
Compare UUIDs, extract time and version from UUIDs
\end{tags}

The library provides operations on UUIDs. Please consult other sources
for understanding UUIDs and the implications of the different UUID
versions. Some typical calls are given below:

\begin{code}
?- uuid(X).
X = 'ea6589fa-19dd-11e2-8a49-001d92e1879d'.

?- uuid(X, [url('http://www.swi-prolog.org')]).
X = '73a07870-6a90-3f2e-ae2b-ffa538dc7c2c'.
\end{code}

\vspace{0.7cm}

\begin{description}
    \predicate[det]{uuid}{1}{-UUID}
\arg{UUID} is an atom representing a new \arg{UUID}. This is the same as
calling \verb$uuid(UUID, [])$. See \predref{uuid}{2} for options.

    \predicate[det]{uuid}{2}{-UUID, +Options}
Create a new \arg{UUID} according to \arg{Options}. The following options
are defined:

\begin{description}
    \termitem{version}{+Versions}
Integer in the range 1..5, which specifies the \arg{UUID} version
that is created. Default is 1.
    \termitem{dns}{DNS}
    \termitem{url}{URL}
    \termitem{oid}{OID}
    \termitem{x500}{X500}
Provide additional context information for UUIDs using version
3 or 5. If there is no explicit version option, \arg{UUID} version
3 is used.
    \termitem{format}{+Format}
Representation of the \arg{UUID}. Default is \const{atom}, yielding atoms
such as \verb$8304efdd-bd6e-5b7c-a27f-83f3f05c64e0$. The
alternative is \const{integer}, returning a large integer that
represents the 128 bits of the \arg{UUID}.
\end{description}

If SWI-Prolog was not built with the OSSP \arg{UUID} dependency library a
simple Prolog alternative that only implements version 4 random
UUIDs is provided. In this case the default version is 4 and the
only admissible options are \verb$version(4)$ and \verb$format(Format)$.

    \predicate{uuid_property}{2}{+UUID, ?Property}
True when \arg{UUID} is a property of the given \arg{UUID}. Supported properties
are:

\begin{description}
    \termitem{version}{V}
Return the version of the \arg{UUID} (1..5)
    \termitem{time}{-Stamp}
Time using SWI-Prolog's time stamp (float with seconds
since January 1, 1970, UTC). Only for version 1 and 2
UUIDs
\end{description}

\begin{tags}
    \tag{To be done}
Implement more properties.
\end{tags}
\end{description}