Update spec.md

spec/spec.md

@@ -47,11 +47,60 @@ dd {
 
 Evaluating the credibiity of digital information about the real world is a difficult problem, one which is not sufficiently addressed by cryptographic signing or blockchain validation.  An open, interoperable, cross-domain web of trust could enable robust credibility assessment; a number of projects pursue this goal.  LinkedClaims is a minimal standard to enable links between independent claims: each claim must be addressable (ie have a URI), must be about an addressable subject, and must be cryptographically signed.  Several desirable features are also identified, such as the ability to make a determinate hash of claim content.  The LinkedClaim pattern already exists in several independent projects and implementations; by defining profiles or mappings for these existing data structures to a LinkedClaim data model, we enable linking them together without requiring changes to their native formats.
 
+This specification defines the fundamental requirements for a claim to be classified as a "linked claim." It introduces the concept of a LinkedClaim profile, outlines how an ecosystem can achieve conformance with the linked claim requirements, and provides guidance on specifying additional requirements through a profile. However, it does not define any specific profile or provide an implementation guide, which are addressed in separate documents.
+
 ## Status of This Document
 
 Decentralized Web Node is a _DRAFT_ specification under development within the [Decentralized Identity Foundation](https://identity.foundation) (DIF). It is an active work item of the [Linked Claim Incubation Lab at DIF](https://github.com/decentralized-identity/labs/blob/main/proposals/linked_claims/001_proposal.md)  It incorporates requirements and learnings from diverse stakeholders across sectors into a shared specification that meets the collective needs of the community.
 
-The specification will be updated to incorporate feedback, from DIF members and the wider community, with a reference implementation being developed within DIF that exercises the features and requirements defined here. We encourage reviewers to submit [GitHub Issues](https://github.com/decentralized-identity/labs-linkedclaims/issues) as the means by which to communicate feedback and contributions.
+The specification will be updated to incorporate feedback, from DIF members and the wider community, with a reference implementation being developed that exercises the features and requirements defined here. We encourage reviewers to submit [GitHub Issues](https://github.com/decentralized-identity/labs-linkedclaims/issues) as the means by which to communicate feedback and contributions.
+
+## Terminology
+
+[[def:Linked Claim]] ~ A structured, cryptographically signed document with a URI subject that is itself addressable at a URI, following at least the MUST requirements detailed below.
+
+[[def:URI]] ~ a Uniform Resource Identifier as defined in https://datatracker.ietf.org/doc/html/rfc3986
+
+## Architecture
+
+```mermaid
+
+graph LR
+    subgraph Claim A
+        A_id["id: URI_A"]
+        A_subject["subject: URI_B"]
+        A_content["content: {...}"]
+        A_sig["signature: xyz"]
+    end
+    
+    subgraph Claim B
+        B_id["id: URI_B"]
+        B_subject["subject: URI_X"]
+        B_content["content: {...}"]
+        B_sig["signature: xyz"]
+    end
+    
+    subgraph Claim C
+        C_id["id: URI_C"]
+        C_subject["subject: URI_B"]
+        C_content["content: {...}"]
+        C_sig["signature: xyz"]
+    end
+
+    %% Claims point to target claim's ID URI
+    A_subject -.-> B_id
+    C_subject -.-> B_id
+    
+    classDef claim fill:#e6e6fa,stroke:#333,stroke-width:2px;
+    classDef claimPart fill:#f0f0f0,stroke:#666,stroke-width:1px;
+    class A_id,B_id,C_id,A_subject,B_subject,C_subject,A_content,B_content,C_content,A_sig,B_sig,C_sig claimPart;
+    
+    style Claim A fill:#e6e6fa,stroke:#333,stroke-width:2px;
+    style Claim B fill:#e6e6fa,stroke:#333,stroke-width:2px;
+    style Claim C fill:#e6e6fa,stroke:#333,stroke-width:2px;
+
+    linkStyle 0,1 stroke:#666,stroke-width:2px,stroke-dasharray: 5;
+```