RDF: Ontology for customised predicates

In solid/constants/schema.dart, we defined a few customised predicates

/// File predicate

const String appsFile = 'https://solidcommunity.au/predicates/file#';

/// Terms predicate

const String appsTerms = 'https://solidcommunity.au/predicates/terms#';

/// Log ID predicate

const String appsLogId = 'https://solidcommunity.au/predicates/logid#';

/// Data predicate

const String appsData = 'https://solidcommunity.au/predicates/data#';

But the description of these predicates does not seem defined anywhere (the pages referred by the above hyperlinks do not exist).

We need to create the ontology to describe these predicates, similar to how the ACL ontology describes the ACL predicates. This ontology needs to be publicly accessible.

The above definition is problematic in the sense that each string variable seems to define a predicate (as implied by the comments and the predicates in URLs) but are actually used as namespace, e.g. we use

https://solidcommunity.au/predicates/terms#sessionKey

Here, https://solidcommunity.au/predicates/terms is effectively a namespace which defines the predicate sessionKey.