The BIM Glossary

Building Information Modelling — a way of working in which a building is created and managed as a structured, queryable database of information, presented as a model. The 'I' is the point: not the geometry, but the reliable data on every object.

A single self-aware element in a BIM model — a wall, door, beam, duct — that carries its own data (type, dimensions, performance, cost, manufacturer) as well as its geometry, and can be scheduled, priced and checked.

The managed flow of information across a project: the client states requirements, the team plans (BEP), everyone produces in a shared Common Data Environment, the information is checked, and it is handed over. Codified by ISO 19650. The 'process' leg of BIM, where most of the value and risk live.

The responsibilities that make BIM collaborative: the appointing party (client), the lead appointed party (coordinating delivery), the task teams (each discipline), and practical roles such as the BIM manager (governs standards and the CDE), the BIM coordinator (runs clash detection) and the modellers. The 'people' leg of BIM.

Computer-Aided Design — drawing on a computer. Each view is drawn independently as lines, kept consistent by human discipline. CAD made drawing faster; BIM replaces the drawing with a model the drawings are cut from.

Several discipline models (architecture, structure, services) combined into one coordinated whole for checking, without merging them into a single file. The basis of clash detection.

The structured, non-geometric data a BIM model carries — what each object is, how it performs, what it costs, who made it, when it needs service. The reason clients ask for BIM, and the part a drawing can never hold.

A drawing generated from a BIM model — a plan is the model cut horizontally, a section cut vertically, a schedule its objects listed. Views are outputs of the model, not separate drawings.

Defined by rules and parameters rather than fixed geometry: change a parameter (a door's width, a wall's height) and the object updates itself, and everything that reads from it updates too.

The principle that there is one authoritative description of the building — the model — from which every drawing, schedule and estimate is generated, so they cannot disagree. In CAD the single source of truth is the fallible human.

The 3D model linked to a construction programme, so the build sequence can be simulated in time — spotting logistics and sequencing problems before site.

The model linked to cost data, so quantities and estimates are drawn from the source rather than measured by hand, and cost tracks design change.

Later, less-standardised 'dimensions' — commonly sustainability/energy (6D) and facility-management/lifecycle (7D). Definitions differ between sources; '8D' and beyond are largely vendor marketing, not formal standards.

Shorthand for the layers of information added to the 3D model: 4D (time), 5D (cost), and — less standardised — 6D and 7D. The dimensions are types of data, not extra geometry; beyond 5D the definitions vary by source.

Placing an object in a shared, industry-standard filing system (schemes such as Uniclass or OmniClass, and the fields COBie requires) so everyone's 'door' means the same thing and software can group, count and exchange objects reliably. Without it, quantities do not add up across a project.

The parametric hierarchy: a family is a category of object (e.g. a single-leaf door), a type is a specific variant (900 mm fire door), and an instance is one placed in the model. Change the type and every instance follows.

How reliable and developed an object's geometry AND information are at a stage — LOD 100 to 500 (BIMForum). Crucially it is Level of DEVELOPMENT, not Level of Detail: it measures how much you can trust the object, not how pretty it looks.

Modelling only to the reliability a model use requires — no more. Over-modelling wastes time; under-modelling misleads. The right level of effort is set by what the information is for.

A specific job the model must do — design coordination, clash detection, quantity take-off, energy analysis, construction sequencing, facility management, visualisation. Model uses decide what to model, to what LOD, with what data; naming them first is how level of effort is set by purpose rather than guessed.

A named value that defines a parametric object (width, height, fire rating, cost) and drives its geometry and data. Change the parameter and the object — and every view and schedule that reads it — updates. Type parameters apply to every instance; instance parameters are unique to one placement.

BIM Collaboration Format — an open way to exchange issues and clashes (a comment, a viewpoint, a location) between tools, without sending the whole model. The conversation layer of coordination.

buildingSMART Data Dictionary — a shared, online library of classifications, properties and allowed values, so that objects and their data can be tagged against agreed, unambiguous definitions. The dictionary behind the language IFC speaks: without it, exchanged data is readable but semantically confused.

Construction Operations Building information exchange — a structured (often spreadsheet) format for handing over the non-geometric asset data an operator needs (spaces, systems, components: what, where, manufacturer, warranty, maintenance), distilled from the model and filled progressively. A container, not a guarantee of quality — only as good as the data discipline behind it.

Information Delivery Specification — an open standard that makes information requirements machine-readable: a precise, computable statement of which objects must carry which properties, in what form. A checker can then validate a model against it automatically, turning data checking from a manual audit into a repeatable test. How the EIR/BEP become verifiable.

Industry Foundation Classes — the open, vendor-neutral data schema for BIM, maintained by buildingSMART. IFC 4.3 (ISO-certified 2024) extended it to infrastructure. Lets a model move between tools without being locked to one vendor.

The ability of different software to exchange model information without losing meaning. The problem openBIM exists to solve; even open exchange loses some fidelity, so it must be planned.

A vendor-neutral approach to BIM built on open standards (IFC, BCF, IDS, bSDD from buildingSMART), so information is exchanged and owned freely rather than trapped in one proprietary format.

BIM Execution Plan — the delivery team's plan for how they will meet the EIR: standards, roles, the CDE, model structure, and milestones. On Indian CPWD projects it is a contractual deliverable within 30 days of award.

The single agreed place where all project information is stored, shared and managed, with a status workflow (work-in-progress, shared, published, archived). The backbone of ISO 19650.

Exchange (or Employer's) Information Requirements — the client's clear statement of what information they need, to what standard and when. The question the BIM Execution Plan answers.

The international standard for managing information over the life of a built asset using BIM. Defines the CDE, roles, and the EIR-to-BEP process. India's CPWD and MoHUA guidelines are aligned with it, though BIS has not published it as an Indian Standard.

Project Information Model (the model built during design and construction) and Asset Information Model (the trimmed, verified information handed over to operate the building). Handover is the PIM-to-AIM transition.

Automatically finding where elements of different disciplines occupy the same space in a federated model (a duct through a beam), so conflicts are resolved on screen, not on site. Powerful, but only as good as the models fed to it.

Using the model's data to simulate performance — energy, structure, daylight, airflow, acoustics — before the building exists. Usually needs an 'analysis-ready' version of the model (clean zones, real properties), and is only as honest as its inputs and assumptions: a comparison of options, not an exact prophecy.

Auditing a model against rules — duplicate/clashing elements, orphaned objects, wrong classifications, missing property sets, naming and LOD compliance — using tools (e.g. Solibri) and increasingly IDS. A routine that is required, assigned and validated at the CDE's gates, turning model quality from a hope into a checked, repeatable gate.

The trustworthiness of a model, in three checkable dimensions — geometry (correct placement, no duplicates/orphans, right classification), data (required properties present and correct), and standards compliance (naming, structure, LOD). Verified by model checking and IDS, not asserted by appearance. A wrong model that looks authoritative is more dangerous than an honestly rough one.

Design for Manufacture and Assembly — designing a building so its parts are manufactured in a factory under controlled conditions and assembled on site (bathroom pods, facade panels, modules). Enabled by BIM (a fabrication-ready LOD 400 model + high coordination); gains speed, quality, safety and less waste — but a model error becomes a manufactured error ('garbage in, garbage manufactured').

Recording the physical site as it actually is — via laser scanning (a dense point cloud of millions of measured points) or photogrammetry (3D from photos). Supports scan-to-BIM (modelling an existing building from reality) and as-built verification (comparing the scan against the design). How the model is held accountable to ground truth.

A live, data-connected virtual replica of a real asset that updates from sensors and is used to monitor and predict its behaviour. Not the same as a BIM model: a BIM model is a design/asset record; a twin is fed by real-time data. The terms are widely — and wrongly — used as synonyms.

Heritage (or Historic) BIM — modelling an existing or historic building, usually from a reality-capture survey (laser scan or photogrammetry), to document, conserve and manage it.

A government requirement to use BIM on public projects — the main engine of adoption, solving the collective-action problem of a fragmented industry (the UK's 2016 'Level 2' mandate was the influential template; dozens of countries now have roadmaps; India's MoHUA mandates BIM on large central projects). A mandate accelerates adoption but doesn't guarantee good BIM — firms can comply on paper and miss the value.

How far an organisation or industry has moved along the path from unmanaged CAD (Level 0) through managed 2D/3D (Level 1) and collaborative BIM (Level 2) toward fully integrated, networked information (Level 3). The Bew-Richards 'wedge'. What climbs is collaboration through managed information — but the levels blur and are being superseded by ISO 19650's language; maturity is really the maturity of the method, not the rung label.

A design approach where, instead of drawing one solution, the designer states goals and constraints (fit this many rooms, maximise daylight, meet these setbacks) and the computer generates and evaluates many candidate solutions against them. A spectacularly fast option-generator and evaluator — but it optimises only for the metrics a human chose, within constraints a human set; it doesn't know what a good building is. Its close cousin is computational/parametric design, which drives geometry by rules and algorithms. Real and useful today; not a replacement for judgement.

The act of making a decision or building work directly from a model's information — taking quantities from it, fabricating from it, operating a building on its data. BIM erodes the old drawing caveats ('don't scale, verify on site'), so good practice states explicitly what each model may and may not be relied upon for, at what level of development, and who verifies. LOD is partly a reliability statement; the danger is a model that looks authoritative being relied on beyond what its makers checked. Liability for reliance is still legally developing.

Treating a BIM model as sensitive information that needs protecting, because a detailed model of a hospital, airport, data centre or government building is an extraordinarily complete description — every structural element, service route and access point — gathered in one shareable file. It means deciding what information is sensitive, controlling who may see which parts (typically through the CDE), and managing information across its life so a convenient shared model doesn't become a gift to someone hostile.