These pages describe the TILDE layout that can be used to describe entities, real or virtual, in the form of a collection of descriptors. This format uses indentation to define a hierchical relationship between descriptors. This is a similar structure similar to YAML but TILDE aims to simplify the description and provide some minor additions.
A TILDE description is a stream of text which exists in a 'container', for example a simple text document. The stream of text comprises a set of descriptors which describe the entity. The container has an identifier and acts as a top level descriptor for the stream.
Descriptors have 4 main components : an indentation reflecting position in the hierarchy, a label, a list of one to many values, with each value having a dictionary of zero to many subsiduary Descriptors. A description is an hierachical arrangement of Descriptors. This model can, for example, be implemented in Python as a group of instances of a 'descriptor' class, but the prime source of the description is the original text stream.
Although there is a Python implementation to create an appropriate data model for a description there is no reason why the model cannot be implemented by other methods at a lower level, for example RDF.
The choice of Descriptors is application dependant. In the examples the use of TILDE is to describe information resources and related entities. Entities such as books, films, websites, services, people, organisations, events, categories, term lists and so forth.
TILDE uses a special character to denote labels, this is the ~ (tilde, U+007E).
A Descriptor is one or more lines of text which have the following form :
So for example :
~language~ english Person~ John Smith date_of_birth~ 18 March 1824 place_of_birth~ Leeds date~of~death~ 9 September 1879 description~ John Smith was the eldest of five children of Samuel Smith, a wealthy butcher and tanner from Meanwood in Leeds. In 1847 John Smith purchased the Backhouse & Hartley brewery in Tadcaster with funding provided by his father. Smith's timing proved fortuitous; pale ales were displacing porter as the public's most popular style of beer, and Tadcaster's hard water proved to be well-suited for brewing the new style. The prosperity of the 1850s and 1860s, together with the arrival of the railways, realised greater opportunities for brewers, and by 1861 Smith employed eight men in his brewing and malting enterprise. note~ Copied from Wikipedia url~ https://en.wikipedia.org/wiki/John_Smith_(brewer)
Descriptors can be defined by the application, however a convention is used in this description is that labels may be of 3 types : an attribute, a property and a cluster.
An attribute has a value which describes the entity. The description can be broken down in more detail using indentation.
A property, which starts and ends with the special character ~ ,describes aspects of a Descriptor. Within the description properties qualify the parent attribute within the description providing information about the value or its creation or update. A value defined in a property also applies to all its subsiduary Descriptors unless it is over-written at a lower level in the hierarchy. Bearing in mind the container is a Descriptor, properties such as the date/time of update or language can be used at the top level to provide information that applies to the whole description. In the example above the property ~language~ applies to the whole description, specifying that the description uses the english language.
A cluster is a special type of attribute that is equivalent to the entity being described and provides a point where all the attributes are grouped together in a description. There may be many clusters in the text stream.
By convention attributes and properties use lower case letters and clusters begin with an upper case letter.
The text stream itself is a set of values and associated subsiduary Descriptors assigned to the system in which the description is being processed. This is why properties at zero indentation applies to the whole description.
Also by convention, the meaning of the additional value lines can be affected by the first character.
In addition there are a number of special Descriptors as follows :
UK_capitals~ ~ London ~ Edinburgh ~ Cardiff ~ Belfast
title~ A Book written~ by~ Joan Collins ~~ Fred Dibnah ~~ Sam Allerdice
# A title and sub-title title~ Hamlet +~ Prince of Denmark # The insertion of a image in a stream of text description~ +~ The Crank Mill was an early implementation of a Boulton and Watt steam engine in a Yorkshire cotton mill. The mill building can still be found near the bottom of Station Road in Morley. insert~ filename-for-an-image-of-the-Crank Mill +~ The power of the steam engine was transmitted into the mill through a shaft driven by a large, mostly uncovered, sun-and-planet crank built on the side of the mill. Hence the name, Crank Mill.
It is important to understand that although these conventions are easy to incorporate into the text stream, they are application driven and must be supported by the software that creates and processes the data model.
# An example of a description for a simple information resource IR~ title~ Introduction to cataloguing and classification sub-title~ A teaching guide with illustrations of major principles for descriptive cataloguing and classification is_a~ book comprises~ text language~ english written~ by~ Bodan S. Wynar published_by~ Colorado Bibliographic Institute date~ 1964 location~ Denver form~ hardback, printed on paper