Cinelab Application Model - cam

In this document, QNames are used to abbreviate URLs (by concatenating the namespace with the suffix). We use the following namespaces:

• @prefix dc: http://purl.org/dc/elements/1.1/
• @prefix cam: http://advene.org/ns/cinelab/
• @prefix pm: http://advene.org/ns/parser-meta/

Generalities

The Cinelab application model defines some higher-level concepts such as annotation types, relation types and schemas, relying on the data model defined in the hypervideo model. The following figure gives an overview of these new element types. It also specifies more precisely some metadata associated to elements of the model.

Cinelab specific elements

Package

In order to ease elements addressing, package elements SHOULD be addressable through the TALES syntax as in the current Advene version. This syntax offers a uniform access to the data model, that can be stored in various ways (XML file, database, etc). Moreover, it allows to use TALES expressions as URL parts, easing the development of REST-based architectures.

Any TALES expression must be evaluated in a given context. This context MUST reference a specific package, named reference package. It MUST be accessible in TALES through the named refpackage. When the TALES expression is used inside of an element content, the reference package is the package that owns the element.

To make them easier to identify, and ease interoperability with other applications, we define a TALES string as a character string that can contain TALES expressions identified with the notation ${...}. This makes it possible to gracefully degrade TALES expression support: applications without TALES support will display the expression, clearly identified. TALES-supporting systems only have to systematically preprend the string: prefix to the character string before sending it to the TALES evaluator.

Metadata

Meaning	Element	API property
prefix/namespace association	pm:namespaces	namespaces

The pm:namespaces metadata is used to simplify URI use, especially for metadata. Its structure is a set of couples (prefix, namespace URI). Each couple is encoded by concatenating the prefix and its URI, separated with a space. Couples are separated by a newline. Using this information, any time a URI is used, the user interface can replace it with a RDF-like QName.

NB: this metadata belongs to a specific namespace, because it has to be specifically processed when seralising/analysing a Cinelab XML package. Instead of being stored as other element metadata, it is encoded/fetched from the XML namespace declarations (xmlns attributes).

Elements

Common metadata

Metadata keys MUST be URIs.

The package and any package element MUST possess the following Dublin Core metadata:

Meaning	Element	API property
Creator	dc:creator	creator
Last contributor	dc:contributor	contributor
Creation date	dc:created	created
Last modification date	dc:modified	modified

Dates MUST be encoding according the ISO 8601 norm, with restrictions specified in http://www.w3.org/TR/NOTE-datetime .

Optionaly, the following metadata MAY be defined:

Meaning	Element	API property
Title	dc:title	title
Description	dc:description	description

TALES Addressing

Any object with metadata MUST expose a TALES attribute meta that offers an access to its metadata through a TALES expression like obj/meta/dc/creator

where dc (in the example) is a prefix declared in the pm:namespaces metadata. More precisely, the pm:namespaces of the reference package for the TALES expression will be used (and not the package owning the element).

Metadata defined by the applicative model can specify a synonym property in the API column, for instance creator for dc:creator. In this case, an equivalent TALES expression can be obj/creator.

Content

A content specifies its MIME type.

Some generic MIME types like application/xml or application/json may specify additional contraints for some content sub-types (as XML schemas or JSON-schemas for instances). A content MAY specify a model attribut that will contain the identifier of a resource whose content will be the appropriate schema.

The following schemas MAY be implemented:

Schema	Content MIME type	Schema MIME type	Schema content
Perl Compatible Regular Expression (PCRE)	text/*	application/x-advene-schema-pcre	A regular expression
RelaxNG	application/xml	application/relax-ng-compact-syntax	A RelaxNG schema in compact notation

Elements

Media

Attributes

Meaning	API property
URL	url
unit (ms, frame...)	unit
origin (in specified unit)d	origin

The only temporal reference that an implementation MUST support uses the “ms” unit (milliseconds), with a 0 origin.

A URL is used to specify the designated media. In the specific case of DVDs, there is no standard to define generic URLs. The model specifies the following format: dvd://title/chapter where title and chapter are optional numbers (defaulting to 1 if not specified). Application should convert this URL to the appropriate format for the used multimedia player.

Metadata

The following metadata MAY be defined:

Meaning	Element	API property
Resource duration	cam:duration	duration
URI	cam:uri	uri

If the URL is not accessible, the URI is used as a key to identify another URL for the same media.

Test

A test is a view that returns a value interpretable as a boolean value. It is notably used to express constraints on elements.

The following MIME type MAY be implemented:

application/x-advene-builtin-test

Test défini en interne par Advene

The builtin test has for content a number of attributes to check. For instance, content-type=text/html. Such a format has the interesting property of being easily introspected, in order to allow automatic GUI generation.

Annotation

Metadata

The following metadata MUST be specified.

Meaning	Element	API property
Annotation type id	cam:type	type

The following metadata MAY be defined:

Meaning	Element	API property
Annotation color	cam:color	TALES string that can be evaluated in the annotation context to get its color

Relation

Metadata

The following metadata MUST be specified.

Meaning	Element	API property
Relation type id	cam:type	type

The following metadata MAY be defined:

Meaning	Element	API property
Relation color	cam:color	TALES string that can be evaluated in the relation context to get its color

Annotation type and relation type

An annotation type (resp. a relation type) is a tag, that has the cam:system-type metadata, with value “annotation-type” (resp. “relation-type”). An annotation (resp. relation) MUST be associated with exactly one annotation type (resp. relation type), and this association MUST be consistent with the annotation (resp. relation) metadata cam:type.

Metadata

The following metadata MAY be defined:

Meaning	Name	Content
Element representation	cam:representation	TALES string that should be evaluated on elements of the type, to get a compact textual representation
Type color	ca:color	TALES string that should be evaluated on the type to get its color.
Element color	cam:element-color	TALES string that should be evaluated on elements of the type, to get their color
Generic constraint	cam:element-constraint	Test view that elements of this type should match
Content type constraint [1]	cam:content-mimetype	String specifying the MIME type for elements of the type
Content model constraint [1]	cam:content-model of the type	Resource specifying the content model for elements of the type

[1]	(1, 2) both metadata (Content type constraint and content model constraint) bring no more expressivity than Generic constraint (which is more generic), but they allow to remove one indirection level (the Test view) for most frequently used constraints.

Schema

A schema is a list whose metadata cam:system-type value is “schema”. A schema represents a description schema, grouping a consistent set of annotation types, relation types and possibly other elements related to the description choices (resources containing content models, tests, associated views...).

Tag

Metadata

The following metadata MAY be defined:

Meaning	Element	API property
Tag color	cam:color	TALES string that can be evaluated in the tag context to get its color

Resources

Core model resources. Some may be hierarchised as in a filesystem. Their identifier will then be prefixed with :userfile: and will encode their path in the identifier by separating directory names with :.

Implementation remarks

Any python object that will have to be handled in the Advene model has to be wrapped in a (temporary) Resource object, so that model consistency is preserved. For efficiency reasons, effective wrapping is carried out lazily.

For instance, a view produces a resource. But if is is included in another view (through TAL for instance), there is no need to transform it into a resource, since it will be consumed (by the including view) before reaching the Advene model level. The including view has to produce a resource, which will be returned to the application.

Dynamic imports

Attributes

Meaning	API property
URL	url
URI	uri

If an URL is not accessible, the URI value can be used by the application to identify another URL for the same package.

If the package loaded at a given URL declares a URI other than specified by the dynamic import, the application SHOULD notify the user to determine the appropriate way to handle this inconsistency (update the dynamic import, or look for the given URI at another URL).