These categories answer the question, Why was the group or item made? The concepts covered include:
Chronology (Was the document made before or after construction?)
The circumstances of the project (e.g., Was the document made to satisfy an academic requirement or to enter a competition?)
The project's specific phase within a building campaign (e.g., Was the document a change order drawing, shop drawing, etc.?)
Researchers often need to find drawings showing a structure as built, or specific proposed designs for a given project. This group of categories allows retrieval at a narrower level, such as all competition drawings for government buildings in France during a given period, or helps refine a query, e.g., when a single project is documented by an unwieldy number of items.
The first of the three categories (Purpose Description) is descriptive, which allows for the expression of nuances or the circumstances that caused the group or item to be created. It can also include expressions compounded from single thesaurus terms. The remaining two categories, Purpose (Broad) and Purpose (Narrow), allow for the expression of broad and narrow terms to provide access points. At the broad level, purpose can be described either as an aid in the design process (i.e., design and construction documents for a project or built work), or as a drawing to record what has already been built (a record document of a built work). At a narrow level, more specific purposes may include exercises, competitions, stages or phases in the design process, or the use (function) for which the item was created, e.g., a change order drawing.
Category: Purpose Description
A narrative statement of the circumstances that caused the group or item to be created.
Volume of details of friezes, probably prepared for publication
Five volumes of as-built designs, made as part of architectural training
Record drawings of Greek classical remains made for engraving and publication in The Antiquities of Athens, I–IV, 1762–1816
Site plan drawn up for the expropriation by the Ville de Paris between 1765 and 1768 of plots of land
This category is meant to allow for the expression of the specific reasons a group or item was created. It is not intended to serve as an access point.
Expressions compounded from a number of thesaurus terms could be included.
Classification of an architectural document in one of two broad types according to its original intended function:
Design and construction documents: documents that are made for a project, that is, during the design and/or construction phase. This type of document is often made in response to a program which contains instructions concerning site, function, materials, or cost. Such documents are used to define ideas for the project, illustrate it, or guide construction. They are part of the design or building process, even if the structure in question was never intended to be built. Examples of types of design and construction documents include: contract drawings, design drawings, shop drawings, capricci.
Record documents: documents of built works, that is, made after the structure has been realized. Such documents record the appearance of built works after they were constructed. Examples of types of record documents are topographical views, measured drawings, record drawings, as-built drawings, reconstructions.
Note that the more precise classifications used as examples are recorded not under this category, but under Purpose (Narrow).
It is frequently difficult to discern the broad purpose of an item. Even so, the fundamental distinction between documents executed for and of a project is a basic one and should be provided when possible. It is more important to furnish the means to retrieve on this broadest level than it is to provide a specific term (e.g., measured drawings), unless the thesaurus being used allows for the broader terms also to be retrieved.
A group of items may have both types of drawings. In that case, both should be recorded, to make retrieval possible through queries for either one.
In the AAT, a hierarchical distinction between design and construction documents and record documents is not made in a way that allows direct retrieval of either type. Compare terms in the Visual Works (VC) hierarchy, starting with [drawings by function]. There, terms for design and construction documents are mixed with terms for record documents. To overcome the difficulty, this category is meant to allow retrieval through queries for either type.
The suggested terminology for this category is:
- design and construction documents
- record documents
optional for groups
core for items
Category: Purpose (Narrow)
A narrower level of description Purpose (Broad), which classifies architectural documents according to
The institutional setting or the function of a document or the conditions under which it was made, such as competitions, exercises, reconstructions
Its stage or phase in the design or construction process, such as preliminary, development, presentation, working, supplemental, or record drawings
The context in which the item was intended to appear, such as book illustrations
Classification of architectural drawings by purpose helps to identify the chronological development or design phases of a project, e.g., (in chronological order) preliminary (conceptual), development (design), presentation, working (e.g., structural), supplemental (shop, change order), record (as-built).
At the more specific levels of terms it may be difficult to distinguish Purpose from other related concepts, such as Method of Representation/Point of View and perhaps even Subject. For example, floor plan may be considered a purpose ("the purpose is to depict a floor plan''), or even a subject ("it depicts a floor of a structure''), but in fact it is more appropriately considered a method of representation/point of view because the plan is a result of a particular viewpoint from which the subject is drawn. The purpose of a floor plan could vary, i.e., it could be a preliminary, working, or record drawing.
In the AAT most of the suggested terms are in the Visual Works (VC) hierarchy, specifically [drawings by function], and the Object Genres (PE) hierarchy. 
Drawings made for projects are part of chronological phases; terms for such phases are appropriate for this category as they show the specific purpose for which an item was made, e.g.,
preliminary or conceptual
- development or design
- mechanical(buildings systems)
- change orders
- record (as-built)
It should be noted, however, that chronological sequence may or may not be part of a given thesaurus structure. When it is not, sorting entries for a large project by design phase may be difficult. Retrieval by the categories associated with Date of Execution, one of the top level categories in Groups/Items, may be of use for chronological sorting.