We can approach the problem of how to form resource descriptions from two perspectives: structuring and writing.

(See §9.1, “Introduction”)

Metamodels describe structures commonly found in resource descriptions and other information resources, regardless of the specific domain.

(See §9.2, “Structuring Descriptions”)

Blobs, sets, lists, dictionaries, trees, and graphs are all kinds of structures that can be used to form resource descriptions.

(See §9.2.1, “Kinds of Structures”)

A list, like a set, is a collection of items with an additional constraint: their items are ordered.

(See §9.2.1.3, “Lists”)

A dictionary, also known as a map or an associative array, is a set of property-value pairs or entries.

(See §9.2.1.4, “Dictionaries”)

Nested dictionaries form a tree.

(See §9.2.1.4, “Dictionaries”)

Trees consist of nodes joined by edges.

(See §9.2.1.5, “Trees”)

JSON consists of two kinds of structures: lists (called arrays in JavaScript) and dictionaries (called objects in JavaScript).

(See §9.2.2.1, “JSON”)

The XML Infoset is a tree structure, where each node of the tree is defined to be an information item of a particular type.

(See §9.2.2.2, “XML Information Set”)

Using schemas to define data representation formats is a good practice that facilitates shared understanding and contributes to long-term maintainability.

(See §9.2.2.2, “XML Information Set”)

The RDF metamodel is a directed graph, so it identifies one node (the one from which the edge is pointing) as the subject of the triple, and the other node (the one to which the edge is pointing) as its object. The edge is referred to as the predicate or (as we have been saying) property of the triple.

(See §9.2.2.3, “RDF”)

An “encoding scheme” is a specialized writing system or syntax for particular types of values. Encoding schemes specify how to textually represent information.

(See §9.3.1, “Notations”)

A writing system employs notations, and adds a set of rules for using them.

(See §9.3.2, “Writing Systems”)

Differences in ordering demonstrate just one way that multiple writing systems may use the same notation differently.

(See §9.3.2, “Writing Systems”)

Syntax is the rules that define how characters can be combined into words and how words can be combined into higher-level structures.

(See §9.3.3, “Syntax”)

The document processing world is concerned primarily with the creation, processing and management of hybrid narrative-transactional documents.

(See §9.4.1, “The Document Processing World”)

In the web world, documents, data, and services are conceptualized as resources, identified using Uniform Resource Identifiers (URI), and accessible through representations transferred via the Hypertext Transfer Protocol (HTTP).

(See §9.4.2, “The Web World”)

The Semantic Web world unifies the concept of a resource as it has been developed in this book, with the web notion of a resource as anything with a URI. Descriptions must be structured as graphs, adhering to the RDF metamodel and relating resources to one another via their URIs.

(See §9.4.3, “The Semantic Web World”)