* @2019-08-18T07:25:58.518Z
<<JMUA68Y4>> Alph Point Selectors (JZGKMF25)

Alph Simple Selectors: POINT Selectors
http://alph.io/selectors/point

Draft J85



Alph POINT selectors are the simplest of the Simple Selectors and are, as you might have inferred already, for numerically referencing an individual point or segment in a stream or collection of media.

As point selectors are zero-length and do not refer to a fragment of media, they may be used to represent a bookmark, play position, cursor location, insertion point, etc.. 
 

Form:

    [media URL]#index



SELECTORS



intPoint

     An integer after the fragment token (#).

Example:

    http://host/path/file#123

Test:

    /\d+/ 

Units:

     text/* — The intPoint represents a zero-based index into the Unicode CODEPOINTS of the text.

    image/* — The intPoint represents a zero-based index into the PAGES of a multi-page image, or the LAYERS of a single-page, multi-layer image.

    audio/* — The intPoint represents a zero-based index into the SAMPLES of a PCM audio stream.

    video/* — The intPoint represents a zero-based index into the FRAMES of a video stream.



floatPoint

     A floating-point number after the fragment token. Surprise, surprise.

Example:

    http://host/path/file#123.456

Test:

    /\d+\.\d+/

Units:

    text/* — n/a

    image/* — n/a

    audio/* — The floatPoint represents a zero-based index into the SECONDS of the audio recording.

    video/* — The floatPoint represents a zero-based index into the SECONDS of the audio recording.



normalPoint

    A floating-point value between 0.0 and 1.0 prefixed by a caret (^) to represent a normalized proportion of the media's contents. For example, a normalPoint of #^0.5 indicates the precise middle point of a text or audio/visual stream.

Example:

    http://host/path/file#^0.11463

Test:

    /\^[0,1]\.\d+/

Units:

    The normalPoint selector is unit-agnostic and represents a proportion of media which servers and clients will have to translate to appropriate units for different media. 

When a proportion is given in a higher precision than the media can be split into, round down. For example, #^0.5 of a 7-codepoint plain-text should point at index 3 ( floor(7*0.5) ).