Spatial networks like transportation, power, and pipeline networks are a ubiquitous spatial concept in everyday life and play an important role for navigational and routing purposes. Database support for large spatial networks in order to represent, store, query, and manipulate them is rare. Our paper aims to provide the beginning of a conceptual, abstract, and formal model of spatial networks, called Spatial Network Algebra (SNA), that includes types and operations and is supposed to serve as a specification for their later implementation in spatial database systems and GIS. Finally, we show how our spatial network concepts can be embedded into an SQL-like query language.