Tuples (class codice 75) are immutable sequences of items of arbitrary types. REBOL datatypes like URLs, emails, date and time values, tuples, strings, tags, etc. The ordered sequential types are lists (dynamic arrays), tuples, and strings. Another way of modeling tuples in Set Theory is as nested ordered pairs. Block addresses are generalized 64-bit pointers that reference (node, drive, blknum) tuples. A relational database consists of sets of tuples with the same attributes. Rows are also called records or tuples. Similarly, queries identify tuples for updating or deleting. These networks match rule conditions (patterns) to facts (relational data tuples). Second, there can't be identical tuples or rows in a table. E.F. Codd originally defined tuples using this mathematical definition. A "relation" is defined as a set of tuples that have the same attributes. Instances of properties are added by application of bootstrapping methods, which collect relation tuples. Specifics include the implicit expansion of tuples and the stateless pattern system. It provides a repository of tuples that can be accessed concurrently.