Abstract. The article presents an innovative concept of applying graph databases in transport information systems. The model of a graph database has been presented together with implementation of data structures and search operations in a graph. The transformation concept of relational model to a graph data model has been developed. The schema of graph database has been proposed for public transport information system purposes. The realization methods have been illustrated by the use of search function based on the Cypher query language.Key words: databases, graph model, information systems in transport.
Application of graph databases for transport purposesA. CZEREPICKI Warsaw University of Technology, Faculty of Transport, 75 Koszykowa St., 00-662 Warsaw to the task of algorithmic path-finding in a graph conditioned by additional restrictions like time, distance, number of changes, etc.Operational efficiency of search algorithms in a graph depends on a graph representation form in computer memory. What refers to most often used data structures are neighbourhood matrices and neighbourhood lists [4,5]. Since traditional databases do not offer their own tools for graph storage, in practice, indirect solutions are applied. In relational databases, conversion of a graph structure into recording in the form of tables and relations is required. Whereas, realization of complex search operations is left to the user.The alternative solution consists of extending the existing functionality of a database by the possibilities to store the graph structures together with execution of basic search operations, as it was the case with GraphGB system originating from object-oriented database [6]. Anyway, all solutions based on existing database systems are burdened with a series of defects, among which we can enumerate, e.g., additional expenses related to data conversion, necessity of operating at a low abstraction level, difficulties with interpretation of data obtained, problems of solution scalability and limited applicability of optimization specific for graphs.Graph Databases belong to the category of databases named NoSQL (Not Only SQL). NoSQL databases use data models other than relational model. They are characterized by high efficiency and scalability, which are obtained by resigning from data integrity or accessibility [7]. The basis of a data model for graph databases is a graph. Most often it is a directed graph (digraph) whose nodes and edges can have attributes [8].Depending on practical realization, graph databases differ each other data storage method and in search algorithm realization methods in a graph [9][10][11]. The present paper limits itself to databases using their own storage and data search methods, at implementing in graph model assumptions. So, adapting a graph model to the needs of ITS systems, can be brought down to the task of path-finding in a graph. In the case of systems using a graph database, there are ensured performance