Add "diff" functionality between objects of same class

[ronaldtse]

Often I want to compare model objects to see if two objects are identical.

The definition of two model objects being identical is:

• They are of the same class (same model)
• Their attributes have identical values (recursive)

I have written a comparator for Shale-based classes in the loc_mods gem.

These are the relevant files:

• https://github.com/relaton/loc_mods/blob/main/lib/loc_mods/cli.rb : the diff print out routines
• https://github.com/relaton/loc_mods/blob/main/lib/loc_mods/comparable_mapper.rb : generating the diff and actual compares
• https://github.com/relaton/loc_mods/blob/main/lib/loc_mods/base_mapper.rb : inserting the comparison methods into the object classes

This task is to port the comparison functionality to lutaml-model, so that objects using lutaml-model are comparable by default.

[ronaldtse]

Example:

Extract this directory which gives you test and test2 directories:
Archive.zip

Run in loc_mods:

$ bundle exec exe/loc-mods detect-duplicates test/
Duplicate set #1 found for URL: https://doi.org/10.6028/NIST.TN.1630
  Comparison 1:
  File 1: test/allrecords-MODS-991000002489708106.xml
  File 2: test/allrecords-MODS-991000091869708106.xml
  Differences:
  └── LocMods::Record
      └── record_info (collection):
          └── [1] (LocMods::RecordInfo)
              └── [1] (LocMods::RecordIdentifier)
                  └── content (Shale::Type::String):
                      ├── - (String) "991000002489708106"
                      └── + (String) "991000091869708106"
  Similarity score: 99.91%

$ bundle exec exe/loc-mods detect-duplicates test2
Duplicate set #1 found for URL: https://doi.org/10.6028/NIST.IR.6659
  Comparison 1:
  File 1: test2/allrecords-MODS-991000009289708106.xml
  File 2: test2/allrecords-MODS-991000179879708106.xml
  Differences:
  └── LocMods::Record
      ├── identifier (collection):
      │   └── - [2] (LocMods::Identifier)
      │       ├── content (Shale::Type::String):
      │       │   └── (String) "994303379"
      │       ├── display_label (Shale::Type::String):
      │       │   └── (nil)
      │       ├── type (Shale::Type::String):
      │       │   └── (String) "oclc"
      │       ├── type_uri (Shale::Type::Value):
      │       │   └── (nil)
      │       ├── invalid (Shale::Type::Value):
      │       │   └── (nil)
      │       └── alt_rep_group (Shale::Type::String):
      │           └── (nil)
      ├── note (collection):
      │   ├── [2] (LocMods::Note)
      │   │   └── content (Shale::Type::String):
      │   │       ├── - (String) "July 1, 2010."
      │   │       └── + (String) "2010."
      │   └── [3] (LocMods::Note)
      │       └── content (Shale::Type::String):
      │           ├── - (String) "Title from PDF title page (viewed June 5, 2017)."
      │           └── + (String) "Title from PDF title page."
      ├── origin_info (collection):
      │   └── [2] (LocMods::OriginInfo)
      │       ├── [1] (LocMods::Place)
      │       │   └── [1] (LocMods::PlaceTerm)
      │       │       └── content (Shale::Type::String):
      │       │           ├── - (String) "Gaithersburg, MD:"
      │       │           └── + (String) "Gaithersburg, MD :"
      │       └── [1] (LocMods::Publisher)
      │           └── content (Shale::Type::String):
      │               ├── - (String) "U.S. Dept. of Commerce, National Institute of Standards and
                Technology;"
      │               └── + (String) "U.S. Dept. of Commerce, National Institute of Standards and
                Technology; "
      ├── record_info (collection):
      │   └── [1] (LocMods::RecordInfo)
      │       ├── [1] (LocMods::Date)
      │       │   └── content (Shale::Type::String):
      │       │       ├── - (String) "190912"
      │       │       └── + (String) "160922"
      │       ├── [1] (LocMods::Date)
      │       │   └── content (Shale::Type::String):
      │       │       ├── - (String) "20200114084208.0"
      │       │       └── + (String) "20160922100247.0"
      │       └── [1] (LocMods::RecordIdentifier)
      │           └── content (Shale::Type::String):
      │               ├── - (String) "991000009289708106"
      │               └── + (String) "991000179879708106"
      ├── subject (collection):
      │   ├── - [1] (LocMods::Subject)
      │   │   ├── id (Shale::Type::Value):
      │   │   │   └── (nil)
      │   │   ├── authority (Shale::Type::String):
      │   │   │   └── (String) "lcsh"
      │   │   ├── authority_uri (Shale::Type::Value):
      │   │   │   └── (nil)
      │   │   ├── value_uri (Shale::Type::Value):
      │   │   │   └── (nil)
      │   │   ├── lang (Shale::Type::String):
      │   │   │   └── (nil)
      │   │   ├── script (Shale::Type::String):
      │   │   │   └── (nil)
      │   │   ├── transliteration (Shale::Type::String):
      │   │   │   └── (nil)
      │   │   ├── display_label (Shale::Type::String):
      │   │   │   └── (nil)
      │   │   ├── alt_rep_group (Shale::Type::String):
      │   │   │   └── (nil)
      │   │   ├── usage (Shale::Type::Value):
      │   │   │   └── (nil)
      │   │   ├── topic (Shale::Type::String):
      │   │   │   └── (Array) [(String) "Jet planes", (String) "Fuel", (String) "Thermal properties"]
      │   │   ├── geographic (Shale::Type::String):
      │   │   │   └── (Array) 0 items
      │   │   ├── temporal (LocMods::Temporal):
      │   │   │   └── (Array) 0 items
      │   │   ├── title_info (LocMods::SubjectTitleInfo):
      │   │   │   └── (Array) 0 items
      │   │   ├── name (LocMods::SubjectName):
      │   │   │   └── (Array) 0 items
      │   │   ├── geographic_code (LocMods::GeographicCode):
      │   │   │   └── (Array) 0 items
      │   │   ├── hierarchical_geographic (LocMods::HierarchicalGeographic):
      │   │   │   └── (Array) 0 items
      │   │   ├── cartographics (LocMods::Cartographics):
      │   │   │   └── (Array) 0 items
      │   │   ├── occupation (LocMods::Occupation):
      │   │   │   └── (Array) 0 items
      │   │   ├── genre (LocMods::Genre):
      │   │   │   └── (Array) 0 items
      │   │   └── href (Shale::Type::String):
      │   │       └── (String) "https://id.loc.gov/authorities/subjects/sh2001009121"
      │   ├── - [2] (LocMods::Subject)
      │   │   ├── id (Shale::Type::Value):
      │   │   │   └── (nil)
      │   │   ├── authority (Shale::Type::String):
      │   │   │   └── (String) "fast"
      │   │   ├── authority_uri (Shale::Type::Value):
      │   │   │   └── (nil)
      │   │   ├── value_uri (Shale::Type::Value):
      │   │   │   └── (nil)
      │   │   ├── lang (Shale::Type::String):
      │   │   │   └── (nil)
      │   │   ├── script (Shale::Type::String):
      │   │   │   └── (nil)
      │   │   ├── transliteration (Shale::Type::String):
      │   │   │   └── (nil)
      │   │   ├── display_label (Shale::Type::String):
      │   │   │   └── (nil)
      │   │   ├── alt_rep_group (Shale::Type::String):
      │   │   │   └── (nil)
      │   │   ├── usage (Shale::Type::Value):
      │   │   │   └── (nil)
      │   │   ├── topic (Shale::Type::String):
      │   │   │   └── (Array) [(String) "Jet planes", (String) "Fuel", (String) "Thermal properties"]
      │   │   ├── geographic (Shale::Type::String):
      │   │   │   └── (Array) 0 items
      │   │   ├── temporal (LocMods::Temporal):
      │   │   │   └── (Array) 0 items
      │   │   ├── title_info (LocMods::SubjectTitleInfo):
      │   │   │   └── (Array) 0 items
      │   │   ├── name (LocMods::SubjectName):
      │   │   │   └── (Array) 0 items
      │   │   ├── geographic_code (LocMods::GeographicCode):
      │   │   │   └── (Array) 0 items
      │   │   ├── hierarchical_geographic (LocMods::HierarchicalGeographic):
      │   │   │   └── (Array) 0 items
      │   │   ├── cartographics (LocMods::Cartographics):
      │   │   │   └── (Array) 0 items
      │   │   ├── occupation (LocMods::Occupation):
      │   │   │   └── (Array) 0 items
      │   │   ├── genre (LocMods::Genre):
      │   │   │   └── (Array) 0 items
      │   │   └── href (Shale::Type::String):
      │   │       └── (String) "https://id.worldcat.org/fast/982434"
      │   └── - [3] (LocMods::Subject)
      │       ├── id (Shale::Type::Value):
      │       │   └── (nil)
      │       ├── authority (Shale::Type::String):
      │       │   └── (String) "fast"
      │       ├── authority_uri (Shale::Type::Value):
      │       │   └── (nil)
      │       ├── value_uri (Shale::Type::Value):
      │       │   └── (nil)
      │       ├── lang (Shale::Type::String):
      │       │   └── (nil)
      │       ├── script (Shale::Type::String):
      │       │   └── (nil)
      │       ├── transliteration (Shale::Type::String):
      │       │   └── (nil)
      │       ├── display_label (Shale::Type::String):
      │       │   └── (nil)
      │       ├── alt_rep_group (Shale::Type::String):
      │       │   └── (nil)
      │       ├── usage (Shale::Type::Value):
      │       │   └── (nil)
      │       ├── topic (Shale::Type::String):
      │       │   └── (Array) [(String) "Jet planes", (String) "Fuel"]
      │       ├── geographic (Shale::Type::String):
      │       │   └── (Array) 0 items
      │       ├── temporal (LocMods::Temporal):
      │       │   └── (Array) 0 items
      │       ├── title_info (LocMods::SubjectTitleInfo):
      │       │   └── (Array) 0 items
      │       ├── name (LocMods::SubjectName):
      │       │   └── (Array) 0 items
      │       ├── geographic_code (LocMods::GeographicCode):
      │       │   └── (Array) 0 items
      │       ├── hierarchical_geographic (LocMods::HierarchicalGeographic):
      │       │   └── (Array) 0 items
      │       ├── cartographics (LocMods::Cartographics):
      │       │   └── (Array) 0 items
      │       ├── occupation (LocMods::Occupation):
      │       │   └── (Array) 0 items
      │       ├── genre (LocMods::Genre):
      │       │   └── (Array) 0 items
      │       └── href (Shale::Type::String):
      │           └── (String) "https://id.worldcat.org/fast/982425"
      └── title_info (collection):
          └── [1] (LocMods::TitleInfo)
              └── [1] (String)
                  └── :
                      ├── - (String) "Thermodynamic, transport, and chemical properties of reference
                JP-8"
                      └── + (String) "Thermodynamic, transport, and chemical properties of reference JP-8
"
  Similarity score: 92.75%

In Lutaml::Model, since we don't know the type of object parsed, we have to generalize it so that the user is able to define the class and then parse files and then do the comparison to print out such a tree.

[ronaldtse]

The compare code is done in #34

Need to provide documentation on how to use the compare.