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Some background
xsd:anyURI datatype
(from http://www.schemacentral.com/sc/xsd/t-xsd_anyURI.html):
The type xsd:anyURI represents a Uniform Resource Identifier (URI) reference. URIs are used to identify resources, and they may be absolute or relative. Absolute URIs provide the entire context for locating the resources, such as http://datypic.com/prod.html. Relative URIs are specified as the difference from a base URI, such as ../prod.html. It is also possible to specify a fragment identifier, using the # character, such as../prod.html#shirt.
The three previous examples happen to be HTTP URLs (Uniform Resource Locators), but URIs also encompass URLs of other schemes (e.g., FTP, gopher, telnet), as well as URNs (Uniform Resource Names). URIs are not required to be dereferencable; that is, it is not necessary for there to be a web page at http://datypic.com/prod.html in order for this to be a valid URI.
foaf:page property
From the 2010 FOAF specification, "The page property relates a thing to a document about that thing. As such it is an inverse of the topic property, which relates a document to a thing that the document is about. A Document class represents those things which are, broadly conceived, 'documents'. The relationship between documents and their byte-stream representation needs clarification – The Documentclass is currently used in a way that allows multiple instances at different URIs to have the 'same' contents (and hence hash)."
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usage: bibo:Website ⊆ dcterms:hasPart only bibo:Webpage
vivo:webpage and vivo:webpageOf properties
The vivo:webpage property relates to an intermediate node (of type vivo:URLLink) that allows specifying the homepage URL as a literal (via the vivo:linkURI data property), as well as a human-readable label ("anchor text") for the link (vivo:linkAnchorText).
vivo:URLLink class
The definition of a vivo:URLLink is listed as, "The Uniform Resource Locator (URL) specifies where an identifier resource is available and the mechanism for retrieving it." An example is given as http://info.slis.indiana.edu/~katy/. A vivo:URLLink is a subclass of an IAO 'information content entity', which is replacing vivo:InformationResource as we transition to the Integrated Semantic Framework, or ISF.
A vivo:URLLink has a data property vivo:linkURI (sub property of vivo:hasValue) for storing the URL, which expects a datatype xsd:anyURI as its value. The VIVO 1.5 ontology vivo:linkAnchorText data property appears to be deprecated in favor of rdfs:label with the transition to the ISF.