Add SPDX Java library family diagram

README.md

@@ -50,6 +50,8 @@ See [README-V3-UPGRADE.md](README-V3-UPGRADE.md) for library upgrade instruction
 
 ## API Documentation
 
+[![SPDX Java library family diagram](spdx_java_lib_family.png)](./spdx_java_lib_family.png)
+
 Here are links to the API documentation for the family of SPDX Java libraries.
 
 "release" points to the API documentation of the latest stable version of the library, while "dev" points to the API documentation generated every time there is an update in the library's GitHub repository.

spdx_java_lib_family.plantuml

@@ -0,0 +1,81 @@
+' SPDX-FileCopyrightText: 2025 SPDX contributors
+' SPDX-FileType: DOCUMENTATION
+' SPDX-License-Identifier: Apache-2.0
+
+@startuml spdx_java_lib_family
+scale 1.5
+
+title Family of SPDX Java libraries
+
+' Left-to-right layout is more familiar for readers of left-to-right languages.
+left to right direction
+
+' Use "package" to group related components and improve readability.
+' This does not imply actual Java package structure.
+package "SPDX Java libraries" {
+    package "Core libraries" as core_pkg {
+        component "<b><size:20>java-spdx-library</size></b>\nCore library & helpers" as lib #LightSalmon
+        component "<b><size:20>spdx-java-core</size></b>\nCore utilities" as core #LightYellow
+        component "<b><size:20>org.spdx.storage.IModelStore</size></b>\nStorage service provider interface" as storeSPI #LightBlue
+        component "<b><size:20>org.spdx.storage.simple.InMemSpdxStore</size></b>\nSimple in-memory store" as inmem #LightBlue
+    }
+
+    package "Models" as model_pkg {
+        component "<b><size:20>spdx-java-model-2_X</size></b>\nSPDX 2 model" as model2 #LightGreen
+        component "<b><size:20>spdx-java-model-3_0</size></b>\nSPDX 3 model" as model3 #LightGreen
+    }
+
+    package "Storage implementations" as store_pkg {
+        component "<b><size:20>spdx-java-tagvalue-store</size></b>\nTag-Value store" as tagvalue #LightBlue
+        component "<b><size:20>spdx-java-rdf-store</size></b>\nRDF store" as rdf #LightBlue
+        component "<b><size:20>spdx-java-spreadsheet-store</size></b>\nXLS spreadsheet store" as sheet #LightBlue
+        component "<b><size:20>spdx-java-jackson-store</size></b>\nJSON / XML / YAML store" as jackson #LightBlue
+        component "<b><size:20>spdx-java-v3jsonld-store</size></b>\nSPDX 3 JSON-LD store" as v3jsonld #LightBlue
+    }
+
+    package "Tooling" as tooling_pkg {
+        component "<b><size:20>spdx-maven-plugin</size></b>\nMaven integration" as maven
+        component "<b><size:20>spdx-model-to-java</size></b>\nJava code generator for SPDX 3 model" as genmodel3
+    }
+
+    package "Specifications" as spec_pkg {
+        component "<i><size:20>spdx-model.ttl</size></i>\nSPDX 3 specification RDF 1.1 Turtle file" as spdx3turtle
+    }
+
+    package "User-facing applications" as app_pkg {
+        component "<b><size:20>tools-java</size></b>\nCommand-line tools" as tools
+        component "<i><size:20>spdx-online-tools</size></i>\nWeb-based tools" as online
+    }
+}
+
+' Core libraries and models
+lib --> core : depends on
+lib --> model2 : depends on
+lib --> model3 : depends on
+
+' Storage SPI and implementations
+core --> storeSPI : contains
+lib --> inmem : contains
+inmem ..|> storeSPI : implements
+jackson ..|> storeSPI : implements
+rdf ..|> storeSPI : implements
+sheet ..|> storeSPI : implements
+tagvalue ..|> storeSPI : implements
+v3jsonld ..|> storeSPI : implements
+
+' Tooling
+maven --> lib : depends on
+genmodel3 --> model3 : generates
+genmodel3 -left-> spdx3turtle : has data file
+
+' User-facing applications
+tools --> lib : depends on
+online --> tools : depends on
+
+' Layout hints
+spec_pkg -[hidden]-> tooling_pkg
+store_pkg -[hidden]-> core_pkg
+inmem -[hidden]-> store_pkg
+model_pkg -[hidden]-> core_pkg
+
+@enduml