# Scope and key concepts This page explains the scope of the Open Fibre Data Standard (OFDS) data model in the context of the three-layer broadband network value chain. It also introduces the key concepts covered in the data model. ```{seealso} * [Data model reference](../reference/data_model.md) ``` ## Scope and focus OFDS data model covers the location of fibre infrastructure, the organisations that own and operate it, and its technical and administrative attributes. To understand the scope and focus of OFDS, consider the layers that make up the broadband network value chain: ````{grid} 2 :margin: 0 :padding: 0 ```{grid-item} **Services** The services consumed by end-users, such as internet, TV and telephony, are not described by the OFDS data model. **Active infrastructure** The active infrastructure over which services are delivered consists of electrical elements, such as lit fibre, access node switches and broadband remote access servers. It is covered by the OFDS data model, which covers the active technologies used in a network, and the organisations that operate the equipment. ``` ```{grid-item}  ``` ```` **Transmission media** The transmission media consists of fibre cables and passive equipment such as splitters, combiners and fibre distribution panels. **It is the primary focus of the OFDS data model**, which describes its physical location, technical characteristics, and ownership. **Supporting infrastructure** The infrastructure that supports the transmission media consists of physical assets such as ducts, poles and pylons. It is also covered by the OFDS data model, which covers its technical characteristics and ownership. ## Nodes and spans `````{grid} 2 :margin: 0 :padding: 0 ````{grid-item} :columns: 4 A network in the OFDS data model is a set of **nodes** interconnected by **spans**. Nodes and spans are spatial entities, also known as features. They consist of a **geometry** that describes their location on the earth's surface, and **attributes** that describe technical and administrative characteristics. ```` ````{grid-item} :columns: 8  ```` ````` ## Location data A node is represented as a **Point** geometry and is defined as: ```{jsoninclude-quote} ../../_readthedocs/html/network-schema.json :jsonpointer: /$defs/Node/description ``` A span is represented as a **LineString** geometry and is defined as: ```{jsoninclude-quote} ../../_readthedocs/html/network-schema.json :jsonpointer: /$defs/Span/description ``` The following examples show how nodes and spans are represented in OFDS's JSON format. The examples include two attributes, `name` and `status`, that are common to both nodes and spans. ````{dropdown} Example: Node :animate: fade-in-slide-down :chevron: down-up ```json { "id": "1", "location": { "type": "Point", "geometry": [-0.174, 5.625] }, "name": "Accra", "status": "operational" } ``` ```` ````{dropdown} Example: Span :animate: fade-in-slide-down :chevron: down-up ```json { "id": "1", "route": { "type": "LineString", "geometry": [ [-0.174, 5.625], [-0.178, 5.807], [-0.112, 5.971] ] }, "name": "Accra to Kumasi", "status": "operational" } ``` ```` ## Linking nodes and spans ````{grid} 2 :margin: 0 :padding: 0 ```{grid-item} Data on nodes and spans are often maintained as separate layers or datasets, without explicit references to describe the nodes to which each span connects. In OFDS, each node is assigned an identifier so that it can be referenced by the spans that connect to it. Explicitly linking nodes and spans means that data users can definitively know that a span connects to a node, without making assumptions based on geographical proximity. ``` ```{grid-item}  ``` ```` ## Organisations and roles The OFDS data model describes three key roles for the organisations involved in a fibre network, each related to a different type of network infrastructure: - **Network providers** operate active network infrastructure (e.g. lit fibre and network switches) - **Transmission medium owners** own transmission media (e.g. fibre cables, splitters and combiners). - **Supporting infrastructure owners** own supporting infrastructure (e.g. ducts, poles and pylons).  These relationships are declared as attributes of both nodes and spans. Therefore, OFDS can represent networks in which: - Different fibre cables are owned by different organisations. - Fibre cables and their supporting infrastructure are owned by different organisations. - Network operators lease dark fibre owned by a different organisation. The following example shows how the different organisation roles are modelled as attributes of a span in OFDS's JSON format. ````{dropdown} Example: Organisation roles :animate: fade-in-slide-down :chevron: down-up In this example, a municipal council owns the duct through which fibre is deployed by a network operator named FibreCo. FibreCo operates its own active infrastructure and leases dark fibre to a second operator named FastNet. ```json { "id": "1", "transmissionMediumOwner": { "id": "1", "name": "FibreCo" }, "supportingInfrastructure": { "type": "duct", "owner": { "id": "2", "name": "Accra Municipal Council" } }, "networkProviders": [ { "id": "1", "name": "FibreCo" }, { "id": "3", "name": "FastNet" } ] } ``` ```` ## Technical attributes In addition to the spatial and organisational characteristics of nodes and spans, the OFDS data model covers various technical attributes, including: ````{grid} 2 ```{grid-item-card} Node attributes * Function within the network (e.g. point of presence, internet exchange point, or add-drop site) * Whether active or passive transmission equipment, which is capable of providing access to the network, is installed * Whether power for active network equipment is available * The active technologies in use (e.g. MPLS) * The type of supporting infrastructure (e.g. a building, pole or pylon). ``` ```{grid-item-card} Span attributes * Fibre type (e.g. G.652) * Fibres count * The active technologies in use (e.g. DWDM) * The transmission rate of the span * The type of supporting infrastructure (e.g. duct, pole or pylon). ``` ```` ## Administrative attributes The OFDS data model also incorporates administrative attributes of nodes and spans, including: - Operational status - Ready for service dates - Availability of dark fibre, co-location space, and capacity for additional fibre cable installation - The phases in which node and spans are deployed, and information on funders and contracts for each phase