diff --git a/src/app/service-graph/services/d3-helpers/graph.helpers.ts b/src/app/service-graph/services/d3-helpers/graph.helpers.ts
new file mode 100644
index 0000000..4bf4cb8
--- /dev/null
+++ b/src/app/service-graph/services/d3-helpers/graph.helpers.ts
@@ -0,0 +1,25 @@
+import * as d3 from 'd3';
+
+export interface Id3BBox {
+  x: number;
+  y: number;
+  width: number;
+  height: number;
+}
+
+export interface IXosGraphHelpers {
+  parseElemClasses (classes: string): string;
+  getSiblingTextBBox(contex: any /* D3 this */): Id3BBox;
+}
+
+export class XosGraphHelpers implements IXosGraphHelpers {
+  public parseElemClasses (classes: string): string {
+    return classes ? classes.split(' ')
+      .map(c => `ext-${c}`)
+      .join(' ') : '';
+  }
+
+  public getSiblingTextBBox(contex: any): Id3BBox {
+    return d3.select(contex.parentNode).select('text').node().getBBox();
+  }
+}