Chapter 10. Architecture

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The diagram below illustrates the internal architecture of Theon and how that is used to manage the live service.

Figure 10.1. Theon Architecture

The central representation of all elements in Theon is the SchemaTree.
The SchemaTree is also the data master for all elements except those contributed by the Schema Factory.
Manipulation of the SchemaTree is carried out indirectly via the XSDDB and through the Generator and Template definitions for the SchemaFactory. The live database system catalog (or a development snapshot of it) can also be used to populate/update the XSDDB and therefore the SchemaTree.
The SchemaTree in conjunction with the XSLT Transforms is converted via the schematic process into different forms suitable for each of the main components of a Theon managed database service (these are called derivations).
The derived DDL is used via Change Management to manipulate/update the live database schema to correspond with the version held in the Schema Tree.
Optionally the derived Config/Python is used by TheonCoupler to control the streams of data being brought into a live database and their subsequent processing.
Optionally the derived JSON is used by both the TheonUI client and server to manage the data on desktops and panels, and the derived SHTML is used by the TheonUI client to manage the presentation of data on desktops and panels.
In a multi-user production service the derived changes are unlikely to be pushed directly into their associated components. Instead the changes would be deferred, for example by release packaging and staged/managed deployment or by central filesystem and controlled snapshot.
In a production multi-user development environment the data masters (the SchemaTree and the SchemaFactory Generator and Template definitions) would be held in the repository of a central version control system to facilitate managed change.