Standardize Graphroot*

[Affie]

Graphroot* Definition (current structure)

*Name TBD

The currently named Graphroot (was GraphRoot and FactorgraphtRoot) is the parent node that contains the factor graph's metadata/ header data and serves as the root for all variables and factors.

Key Characteristics:

• Parent of Variables, Factors, and edges ─ alongside Agent and Blobstore.
• Contains label, description, tags, bloblets, and blobentries
• Serves as the metadata/header container for a factor graph.

Structure:

DFG
├── Graphroot
│   ├── Variables
│   ├── Factors
│   └── Edges
├── Agent
└── Blobstore

Not to be confused with the factor graph structure itself (variables + factors + edges), which are children of Graphroot and accessed by functions such as getVariables, getFactors, and listNeighbors

Naming Options for this metadata/header only structure:

• Graphroot
• Graphheader
• Graphhead
• Graphinfo
• Graphnode
• Graphmeta*
• Graphmetadata*

• metadata can be confused with Metadata found in Blobentry

Field changes

	old field	new field	change reason
✓	label::Symbol	label::Symbol	Unchanged
✓	description::String	description::String	Unchanged
✓	tags::Vector{Symbol}	tags::Set{Symbol}	tags is a Set
✓	metadata::Dict{Symbol, MetadataTypes}	bloblets::Bloblets	#1105
✓	blobEntries::OrderedDict{Symbol, Blobentry}	blobentries::Blobentries	Drop camelCase

[Affie]

I think we should defer the exact structure and naming decision until we see if the current implementation is the best, ie. Graph contains a reference to the variables and factors and therefore, getGraph[Root*] only returns the root (or a reference) and variables and factors are not included.

An alternative can be to add an extra Graph struct (GraphsDFG basically does this):

struct Graph
    root::[Graphroot|Graphheader|Graphmeta] # or flattened label, tags, bloblets, blobentries, description
    variables::Dict{Symbol, Variable} # or factorgraph
    factors::Dict{Symbol, Factor}     # /
end

or change GraphsDFG internals

struct Graph
    label::Symbol
    description::String
    tags::Set{Symbol}
    bloblets::Bloblets
    blobentries::Blobentries
    variables::Dict{Symbol, Variable} # or factorgraph
    factors::Dict{Symbol, Factor}     # /
    #...
end

---

Update:

• Since we already have a AbstractDFG, I would not add extra structure.
• Since we want a concrete type for Graphroot, I would not change the GraphsDFG internals.

[dehann]

Why does GraphRoot have two Nouns?

What is the relation between Factorgraph and GraphRoot?

---

I'm quite confused why there are suddenly new Nouns, Header, Metadata, Meta, Info, Root?

Previously we only had the field .metadata and Noun Blobentry. You are opening a can of worms on BlobInfo, BlobMeta, BlobHeader, etc. Again double nouns... All these suggestions are hyper-generic and in conflict with the existing structure. This seems like a big divergence from what was DFG v1.0 path.

Please tell you are not just dumping chatgpt output as replacement for the design process?

[Affie]

I fixed the first comment options to not be camel case (force of habit). The node is currently called GraphRoot, it needs a better name. I did consider a new generic noun for "common node fields" but It's only handy for the GraphRoot case.
Two similar nouns are currently in use:

• Info - in getDFGInfo
• Metadata/DFGMetadata/GraphMetadata in saveMetadata, [un]packDFGMetadata, overwriteDFGMetadata, copyGraphMetadata - bad name as it originates from copying all UserData RobotData and SessionData

Dehann, I see you added Factorgraph to the wiki. Remember we don't get notifications if you change the wiki, so a heads up would be nice in the future for fundamental changes like that. I recall you preferred just Graph and that is why we have functions such as getGraphBlobentries as I agreed (as apposed to getFactorgraphBlobentries). Did you change your mind on just Graph? I still prefer just Graph a lot more because its shorter and still accurate. I would suggest you open a new issue if you would like to rename the Graph noun to something else. For now I'll stick to the last decision of Graph. For me a factor graph is the collection of variables, factors, and edges.

[Affie]

GraphRoot is now Graphroot (PR) and the first comment was updated accordingly. Graphroot is intended more for internal use -- DFG.getGraphroot -> Graphroot (Graph implied) -- as normal users will use crud such as:

• listGraphs
• getGraphBlobentry
• getGraphBloblet
• getVariable (Graph implied)
• getFactor (Graph implied)

#1183 (comment) will still be considered, but so far having a concrete root/header/metadata type has an advantage.