Hierarchical Information Model
The Hierarchical Information Model (HIM) is an initiative by COVESA to define a syntax for how to define taxonomies containing different types of information. The documentation, source code and releases can be found in the HIM github repository.
The information of a domain that is described using HIM is represented in a graph made up of a tree structure with parent-child relationships,
as shown in Figure 1.
*Figure 1. HIM graph structure
The model provides a structured solution to a scenario where an entity, e. g. a server, manages multiple domain taxonomies.
A domain can in the HIM context be defined with the help of two dimensions:
- a ‘coherent’ dimension which represents information related to something that is logically coherent.
- Examples are a car, a truck, a trailer, an airplane, etc.,
- an ‘information type’ dimension that is used in the description of a coherent dimension using a specific information type.
- The currently defined information types are listed below.
- Resource data
- Service data
- Type definitions
- The currently defined information types are listed below.
HIM specifies rule sets for the different information types that can then be used to define taxonomies for different coherent domains.
The creation of taxonomies for different domains is not done within the HIM project, it is expected to be done by other projects using the HIM rule sets. One example of such a project is the Vehicle Signal Specification project.
The documentation is structured in the different rule sets shortly described below.
HIM Resource Data Rule Set
Rules for describing resources that can be represented by static or dynamically changing data values.
HIM Service Data Rule Set
Rules for describing services that can be represented by procedure signatures.
HIM Type Definition Rule Set
Rules for describing complex datatype definitions, specifically struct definitions.
HIM Configuration Rule Set
Rules for how a set of domain taxonomies is defined.
HIM Common Rule Set
Rules that are commonly used in the other rule sets.
Heritage
The ideas behind HIM originated in the COVESA VSS project, when interest started to be raised for using it for of not only resource data but also service data, and for different domains than the legacy VSS passenger car domain. This may explain why examples in this documentation are often taken from that domain.