From consistency to flexibility: Handling spatial information schema thanks to a middleware in a 3D city modeling context

Abstract

Twinning elements of reality gains a growing interest in support of decision‐making, learning, and simulations: a single and shared model should provide a unique integrative basis for managing assets of any replica of the real world. From a technical viewpoint, sharing and opening information requires both an exchange format and a high degree of freedom and flexibility. It should allow an important number of users to manage this information, to modify it, etc. Storing and manipulating spatial information concerning the urban built context currently focuses on ensuring consistency thanks to relational databases and predefined schemas. Following a paradigm shift from a relational database to a NoSQL database, a schema validation middleware is proposed to improve the flexibility of storage by conceding a share of its consistency. The flexibility improvements thus provide users a common basis that is able to evolve all along the lifecycle of their models and applications as required for twinning things. It allows users and their applications to take advantage of new storage features such as common: versioning, partitioning, prioritization, applications profiles, etc. The middleware and their new capabilities are illustrated thanks to the CityJSON encoding and its simplified schema for a document‐oriented database.

Towards a multi-database CityGML environment adapted to big geodata issues of urban digital twins

“…As CJDB implementation, the abstract city object class has a predefined structure while children thematic objects (buildings, vegetation, etc) are stored in BSON (binary JSON) documents following CityJSON schema without anyconstraints and so no guaranteed consistency. To handle this issue, (Nys and Billen, 2023) propose a middleware called "Cerbere" between the database and the client applications. The entire CityGML schema is implemented in Cerbere so that every transaction is validated to maintain the database compliance with CityGML.…”

“…Figure 3. Example of the bi-directional filter principles of Cerbere (Nys and Billen, 2023) This middleware serves a dual purpose: ensuring consistency and delivering relevant information to each application. Unlike the database, which merely acts as a storage repository without guaranteeing data integrity, developers play a critical role in enforcing consistency through their code.…”