Registration (Jackrabbit Oak 0.9-SNAPSHOT API)

+ + +

Overview
+ + + + Jackrabbit Oak +
+ + + + License +
+ + + + Downloads +
+ + + + From here +
Concepts and architecture
+ + + + Overview +
+ + + + Understanding the node state model +
+ + + + Microkernel +
Using Oak
+ + + + Getting Started +
+ + + + Differences to Jackrabbit 2 +
+ + + + Dos and don'ts +
+ + + + When things go wrong +
Developing Oak
+ + + + Getting Started +
+ + + + Participating +
+ + + + API docs +
Links

+ + + +

+ +

+ + + + +

+ +

+ + +

+ +

Note: Below algorithms turns out to be not sufficient. The edit script for the following case is incomplete. Given S constructed from an empty tree

+ +

S = +/s:{} +/t:{}
+

obtain T from S by

+ +

T = S +/s/a:{} >/s:/t/s
+

Running below algorithm on S and T will result in an edit script which, when applied to S, will not create child node a. I.e. it will result in

+ +

S >/s:/t/s
+

An algorithm for creating edit scripts (in JSOP format) from two trees. See this GitHub repository for a proof of concept implementation and the related discussion on oak-dev@

+ +

// Global variable holding the JSOP journal after the diffTree below returns.
+jsop = ""
+
+/*
+  Create a JSOP journal, which when applied to tree S will transform
+  it to tree T.
+*/
+diffTrees(S, T) {
+  // Create a location (trash) which will temporarily hold removed nodes.
+  // This is necessary since these (or child nodes thereof) might still be
+  // needed in move operations occurring only later in the differencing process.
+  X = S.addNode(createUniqueName)
+
+  // The main differencing process starts at the roots of the trees and
+  // progresses recursively level by level.
+  diffNodes(X, S, T)
+
+  // Remove the trash location and all its content
+  jsop += "-" + X.path
+}
+
+/*
+  Recursively create JSOP operations for the differences of the children
+  of trees S and T. Tree X serves as trash.
+*/
+diffNode(X, S, T) {
+  deleted = S.childNames \ T.childNames   // set difference
+  added   = T.childNames \ S.childNames
+
+  // Need to take care of deleted nodes first in order to avoid
+  // name clashes when adding new nodes later.
+  for (d : deleted) {
+    t = S.child(d)
+
+    // Deleted nodes are moved to trash.
+    op = ">" + t.path + ":" + X.path + "/" + createUniqueName
+    jsop += op
+    S.apply(op)               // Transform S according to the single op
+  }
+
+  for (a : added) {
+    t = T.child(a)
+
+    // assume we can detect a copied node and know its source node
+    if (isCopied(t)) {
+      op = "*" + t.sourceNode.path + ":" + t.path
+    }
+
+    // assume we can detect a moved node and know its source node
+    else if (isMoved(t)) {
+      op = ">" + t.sourceNode.path + ":" + t.path
+    }
+
+    // this is an added node
+    else {
+      op = "+" + t.path
+    }
+
+    jsop += op
+    S.apply(op)               // Transform S according to the single op
+  }
+
+  // assert S.childNames == T.childNames
+  for (c : T.childNames) {
+    diffNode(X, S.child(c), T.child(c))
+  }
+}
+

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