Parts

A BOLTS repository contains a various sorts of data about objects, that are in some way useful in CAD. A part is a object that can be described by a set of dimensions. E.g. a piece of paper is described by its width of 210mm and its height of 297mm.

Classes

However, one often encounters parts that are very similar to each other, for example just differing in their dimensions. These parts can then be more efficiently described as a class of parts. To continue with the paper example, a class describing pieces class could also contain a part with width 100mm and height 100mm.

In a blt-file classes of parts are described, because this case is so frequent. Some parts are one of a kind, so it is not uncommon to have classes that contain just a single part.

The classes of technical parts that BOLTS deals with are often specified by standards issued by standardization bodies. This can be specified for a class in the blt-file.

Collections

It turns out to be convenient to organize the classes of a bolts repository in collections. A collection usually has one or few authors, the parts contained are in some sense related to each other and all the data of a collection is under the same licence.

Each collection has a one word identifier, the collection id. The collection id is the filename (without extension) of the blt-file with the information about the collection, and also explicitly specified in the blt-file. For more details information see there.

The data directory

The data directory contains a number of blt-file, one for each collection. These files contain the backend independent information about the parts in the repository.

The databases

A database directory is a directory that contains data about certain aspects of the parts or data in a specific form.Backends can access this data to transform the parts data into specific forms or collect information.

In contrast to the data in the blt-file, the data in the database directories is optional. If for a class this data is not available, the backend has to be able to deal with it in an appropriate manner, for example by not processing this class.

Backend

A backend is a process that uses backend independent data and data from database, transforms this data and outputs a set of files. This output is called the distribution.

Am example for a backend would be a process that uses the backend independent data about parts, their geometries and dimensions together with a number of templates and stylesheets and produces a set of HTML pages with a nicely rendered, browsable description of the parts. Other backends could produce data that is suitable for use in specific CAD applications.

Backends are not specified in detail by this specification.

Backend independent data - the blt file

The backend independent data is stored in yaml files with the extension .blt. These files contain exactly one YAML document consisting of an associative array with the following keys:

• id: mandatory, string. The id of the collection. Must be identical to the filename of the blt file without the extension.
• name: optional, string. A name for the collection.
• description: optional, string. A description of the contents of this collection.
• author: mandatory, string or list of strings. The author of this collection with e-mail in <>. If multiple authors contributed significantly to this collection a list of authors may be given.
• license: mandatory, string. The name of the license for this collection and a URL pointing to the full text of the license enclosed in <>. Must be one of the supported-licenses.
• blt-version: mandatory, number. The version of the blt format this collection follows.
• classes: mandatory. An list of class-element.

The filename without the .blt extension is called the collection id. For consistency they are repeated in the id field. Collection ids are one word identifiers, which must be unique within the repository. They should contain only letters, numbers and underscores, and should be descriptive, as they may be visible to the user. Some names can not be collection ids: common, gui, template

Parameter Collection

Parameter Collection is the process of assigning a value to each parameter. The set of all parameters is found by collecting parameter names from the fields of one or more parameter-element:

• The keys of the literal field.
• The items of the free field.
• The index field of the table-element s in the tables field.
• The columns field of the table-element s in the tables field.
• The rowindex field of the table2d-element s in the tables2d field
• The colindex field of the table2d-element s in the tables2d field
• The result field of the table2d-element s in the tables2d field

It is an error condition if there is a parameter name present as a key in the types field, that is not in the set of all parameters.

Then a value is assigned to each parameter. This can happen by:

• A literal value given in the literal field
• User or external input for parameters listed in the free field
• Table lookup for parameters listed in the columns field of a table-element
• Table2d lookup for parameters listed in the result field of a table2d-element

It is an error condition if a parameter is not assigned a value or if there is more than one way to assign a value.

The parameter values collected in this way are for example used (among other properties) to populate the template given in the naming-element.

Base Files

Base files are yaml files, in which information about the files for a collection in a database directory are stored. They consist of a list of base-file-element, one for each file they describe.

Base module element

A base module element is a associative array describing an OpenSCAD module with the following keys:

• name: mandatory, string. The name of the module.
• arguments: mandatory, list of strings. A list with the arguments that need to be supplied to the module, in the correct order. Is a subset of the parameters of the class, see parameter-collection.
• classids: mandatory, list of string. A list of class ids for which this base module should be used.
• parameters: optional, parameter-element: Additional basespecific parameters. These parameters allow to represent additional parameters, which are not specific to the class, but to the base. This allows e.g. to let the user choose between a detailed and a schematic representation of the part.
• connectors: optional, base-module-cs. Information about the connectors attached to the part.

Base module connectors

A base-module-cs describes a set of local coordinate systems or connectors that are attached to specific points of the part to allow easy positioning. This is implemented by a OpenSCAD function that returns a coordinate system structure. This function has all the arguments of the module in which the base-module-cs is contained, and an additional argument "location" as the last argument. A base-module-cs is an associative array with the following keys:

• name: mandatory, string. The name of the function that returns the connectors.
• arguments: mandatory, list of strings. A list with arguments that need to be supplied to the connector function in the right order. Is a subset of the parameters of the class and "location", the latter of which must be present.
• locations: mandatory, list of strings. A list of possible values that can be supplied for the argument "location" of the function.

Base function element

A base function element is a associative array describing a python function with the following keys:

• name: mandatory, string. The name of the function.
• classids: mandatory, list of string. A list of class ids for which this base module should be used.
• parameters: optional, parameter-element: Additional basespecific parameters. These parameters allow to represent additional parameters, which are not specific to the class, but to the base. This allows e.g. to let the user choose between a detailed and a schematic representation of the part.

Base object element

A base object element is an associative array describing an object in a FreeCAD Document. It has the following keys:

• objectname: mandatory, string. The name of the part in the document.
• classids: mandatory, list of string. A list of class ids for which this base part should be used.
• parameters: optional, parameter-element: Additional basespecific parameters. These parameters allow to represent additional parameters, which are not specific to the class, but to the base. This allows e.g. to let the user choose between a detailed and a schematic representation of the part.
• proptoparam: optional, associative array of associative arrays. This maps properties of objects to parameters. Keys to the first level of associative arrays are the object names in the source file, keys to the second level are the names of the properties and the values are the names of the parameter as specified in a parameter-element. Defaults to {objectname : {"Label" : "name"}}

Base designtable class element

A designtable class element specifies the classes that should be included in a designtable.

• classid: mandatory, string. A classid that should be included in this designtable.
• naming: optional, naming-element. This describes the form of the configuration names in the design table. If absent, the naming field of the class is used.