Sequences as a basis for pattern language composition

Pattern languages have begun to appear and mature as a presentation of the structures and processes that support the building of complex software systems. A pattern language describes how to compose structures in a particular domain such as telecommunications, client-server architecture, or object-oriented programming, to achieve system-level architectures that are greater than the sum of their parts. A problem lurks on the horizon: How do you compose patterns from multiple domains-from multiple pattern languages-in a single system? For example, today there is nothing other than an ad hoc approach to combining the pattern languages for telecommunications and for object-oriented design to build object-oriented telecommunications systems from the respective pattern languages. To understand the solution to this dilemma, it pays to examine sequences: an important aspect of pattern application that is often overlooked. Sequences are the loci of concern about interleaving patterns, whether from a single pattern language or multiple pattern languages. Sequences are critical because pattern languages represent long-term archives of the rhythms of critical, recurring sequences.