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The Spatial Archive and Interchange Format (SAIF, pronounced ''safe'') was defined in the early 1990s as a self-describing, extensible format designed to support interoperability and storage of geospatial data. SAIF Dataset SAIF has two major components that together define SAIFtalk. The first is the Class Syntax Notation (CSN), a data definition language used to define a dataset's schema. The second is the Object Syntax Notation (OSN), a data language used to represent the object data adhering to the schema. The CSN and OSN are contained in the same physical file, along with a directory at the beginning of the file. The use of ASCII text and a straightforward syntax for both CSN and OSN ensure that they can be parsed easily and understood directly by users and developers. A SAIF dataset, with a .saf or .zip extension, is compressed using the zip archive format. Schema Definition SAIF defines 285 classes (including enumerations) in the Class Syntax Notation, covering the definitions of high-level features, geometric types, topological relationships, temporal coordinates and relationships, geodetic coordinate system components and metadata. These can be considered as forming a base schema. Using CSN, a user defines a new schema to describe the features in a given dataset. The classes belonging to the new schema are defined in CSN as subclasses of existing SAIF classes or as new enumerations. A ''ForestStand::MySchema'' for example could be defined with attributes including age, species, etc. and with ''ForestStand::MySchema'' specified as a subclass of ''GeographicObject'', a feature defined in the SAIF standard. All user defined classes must belong to a schema, one defined by the user or previously existing. Different schemas can exist in the same dataset and objects defined under one schema can reference those specified in another. Inheritance SAIF supports multiple inheritance, although common usage involved single inheritance only. Object Referencing Object referencing can be used as a means of breaking up large monolithic structures. More significantly it can allow objects to be defined only once and then referenced any number of times. A section of the geometry of the land-water interface could define part of a coastline as well as part of a municipal boundary and part of a marine park boundary. This geometric feature can be defined and given an object reference, which is then used when the geometry of the coastline, municipality and marine park are specified. Multimedia Multimedia objects can also be objects in a SAIF dataset and referenced accordingly. For example, image and sound files associated with a given location could be included. == Model Transformations and Related Software Applications == The primary advantage of SAIF was that it was inherently extensible following object oriented principles. This meant that data transfers from one GIS environment to another did not need to follow the lowest common denominator between the two systems. Instead, data could be extracted from a dataset defined by the first GIS, transformed into an intermediary, i.e., the semantically rich SAIF model, and from there transformed into a model and format applicable to the second GIS. This notion of model to model transformation was deemed to be realistic only with an object oriented approach. It was recognized that scripts to carry out such transformations could in fact add information content. When Safe Software developed the Feature Manipulation Engine (FME), it was in large measure with the express purpose of supporting such transformations. The (FMEBC ) was a freely available software application that supported a wide range of transformations using SAIF as the hub. The FME was developed as a commercial offering in which the intermediary could be held in memory instead of as a SAIF dataset. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Spatial Archive and Interchange Format」の詳細全文を読む スポンサード リンク
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