Modelling web resources Ketil Albertsen, Paradigma project National Library of Norway
Aggregates • Documents (in a bibliographic sense) spread over multiple web pages • Web pages consisting of multiple visual/sound components, or traditional multipart documents • Web pages requiring a style sheet, font file etc. for presentation (not directly visible to user) • Snapshots of a web page varying with time, the web version of integrating resources.
Aggregates • Web documents available in multiple formats: HTML, PDF, DOC, … • Web pages providing information in alternative languages or adapted to several web browsers • Blogs and similar pages, the web version of incrementally issued continuing resources • Expressions based on multiple creative efforts: A song (melody + text), rewritings, …
Claim: “Implicit” aggregates, based on objects having some common attribute value, are not sufficient • Inspecting candidate objects for common attribute values is costly, even when using indexes. • Access to attributes may require document interpretation, requiring knowledge of the format. • An aggregate may span only a subset of objects having a given attribute value. • Many aggregates are not based on stored, common object attributes. • Aggregates frequently need an ID and possibly a bibliographic description.
Solution: Aggregate objects, ”boxes” • General container objects holding (references to) other objects. • Boxes can be identified and described as composite objects. • The model defines classes of boxes, each class identifying a set of structural properties. • The application/user may identify multiple applications of each box class.
Box classes (suggested) • • • Component: Ordered, all components presented Variant: Unordered, one of several. Synchronous: Parallel presentation in real time. Update: Later components replace earlier ones, “integrating” CR Extension: Later components are added to earlier ones, “successively issued” CR. • Based On: One component is a further development of one or more other components. • Fragment Of: One component is part of another one.
Box class properties • Cardinality, i. e. 1: n, m: n, 1: 1 • Existence, i. e. will removal of one component imply removal of another • Dependency, e. g. a component depends on a whole • Recursion, e. g. a chapter may contain subchapters • Ordering, usually in time or space • Reference, does a dependent component have an independent value or is it integrated with the other object?
Other Paradigma extensions • Agent objects, for modeling real world objects that cannot themselves be digitized. • Point/fragment reference objects (further discussed tomorrow)
Скачать презентацию Modelling web resources Ketil Albertsen Paradigma project National
0394abdddefe29ec799af9516a03d1ce.ppt