Remove-OSSIM.md

@@ -42,6 +42,79 @@ Benefits:
 
 ## Presentation of the new architecture
 
+### The new ImageMetadata object
+
+To replace OSSIM's MetadataDictionary, a new *ImageMetadata* object is
+introduced. It inherits from *ImageMetadataBase*.
+
+```mermaid 
+classDiagram
+  class ImageMetadataBase
+  ImageMetadataBase : - NumericKeys
+  ImageMetadataBase : - StringKeys
+  ImageMetadataBase : - LUT1DKeys
+  ImageMetadataBase : - LUT2DKeys
+  ImageMetadataBase : - TimeKeys
+  ImageMetadataBase : - GeometryKeys
+  ImageMetadataBase : - ExtraKeys
+  ImageMetadataBase : - [] operator(key)
+  ImageMetadataBase : - Add(key, value)
+  ImageMetadataBase : - Remove(key)
+  ImageMetadataBase : - Has(key)
+  ImageMetadataBase : - ToKeywordList(kwl)
+  ImageMetadataBase : - FromKeywordList(kwl)
+  ImageMetadataBase : - Fuse(imd)
+
+  class ImageMetadata
+  ImageMetadata : - Bands
+  ImageMetadata : - slice(start, end)
+  ImageMetadata : - append(imd)
+  ImageMetadata : - compact()
+  ImageMetadata : - Merge(imd)
+  ImageMetadata : - AppendToKeywordLists(kwlv)
+  ImageMetadata : - AppendToBandKeywordLists(kwlv)
+  ImageMetadata : - FromKeywordLists(kwlv)
+
+  ImageMetadataBase <|-- ImageMetadata
+  ImageMetadata "1" *-- "0..*" ImageMetadataBase
+```
+
+*ImageMetadataBase* encapsulates seven std::map to store seven
+different kind of metadata:
+
+- Numeric metadata for the metadata that can be stored as a double
+- String metadata for the metadata that can be stored as a std::string
+- LUT 1D metadata the metadata that can be stored as a one
+  dimension table
+- LUT 2D metadata for the metadata that can be stored as two
+  dimensions table
+- Time metadata for the metadata that can be stored as a *time* object
+- Geometry metadata for the metadata that represent a model
+- Extra metadata for non generic metadata stored as std::string
+
+The keys of the maps are described in the file otbMetaDataKey. This
+file also defines the *time* object.
+
+The *ImageMetadataBase* class also provides 4 methods:
+
+- the *[] operator* for a read-only access the metadata from the key
+- the *Add* method to set a metadata value
+- the *Remove* method to delete a metadata value
+- the *Has* method to test if a key has a value
+
+The *ImageMetadata* class is used to store the metadata. It contains a
+std::vector *Bands* that contains one *ImageMetadataBase* for each
+band of the product. The metadata that are common to all the bands are
+stored in the *ImageMetadata* object itself. It also provides some
+useful methods:
+
+- the *slice* method to access the metadata of a range of bands
+- the *append* method to concatenate two *ImageMetadata* objects
+- the *compact* method to put to the top level the metadata that are
+  common to all the bands
+- the *Merge* method to merge with another *ImageMetadata*
+
+
 ### Metadata parsing
 
 Here is a new workflow to replace the current function
@@ -54,7 +127,7 @@ Here is a new workflow to replace the current function
    a (in-memory) XML tree. This tree is given to a
    ImageMetadataInterface (IMI) that will look for needed
    information. The parsing is be done by different classes,
-   ddepending on the file format. They can all derive from the base
+   depending on the file format. They can all derive from the base
    class MetadataSupplierInterface. The three suppliers are:
    * GDALImageIO will use GDALDataset::GetMetadata() to extract
      'key=value' pairs and format them into a XML tree.
@@ -62,7 +135,7 @@ Here is a new workflow to replace the current function
      ("ReadXMLToList" method from the "GDALMDReaderBase" class) to
      convert the XML file into a GDAL ListString, which is a
      succession of 'key=value' pairs.
-   * TextMetadataSupplier trys to parse 'key=value' pairs.  
+   * TextMetadataSupplier tries to parse 'key=value' pairs.  
    
    Those classes all implement the method *GetMetadataValue* which
    returns the value of the metadata from a given key. The base class
@@ -72,9 +145,9 @@ Here is a new workflow to replace the current function
 1. The GDAL input/output capabilities are encapsulated in the
    GDALImageIO class, which derivates from ImageIO. This class is in
    charge of fetching the metadata from the product (supplier
-   capabilities hinerited from the class MetadataSupplierInterface),
-   and of writting the metadata to the product (storage capabilities
-   hinerited from the class MetadataStorageInterface).
+   capabilities inherited from the class MetadataSupplierInterface),
+   and of writing the metadata to the product (storage capabilities
+   inherited from the class MetadataStorageInterface).
 
 1. We use a classic IMIFactory to find if a given IMI (associated to a
    given sensor) can parse the metadata of a product. The IMI's