diff --git a/import.go b/import.go
index b2c2a4e..2fd5e9e 100644
--- a/import.go
+++ b/import.go
@@ -1 +1,50 @@
 package cdr
+
+import (
+	"encoding/csv"
+)
+
+// Some assumptions on our input, since encoding/csv reads everything as string. We expect 17 entries per line:
+// cid,time,type,cli,from,to,account,usage,costs,source,destination,leg,reason,package,package_costs,network_costs,service_costs
+//
+//   - cid is free text, could be argued to be unique, but there are no guarantees.
+//   - time is a timestamp formatted YYYY-MM-DD hh:mm:sd
+//   - type is in {Voice,Data,SMS}, of course the header line is "type"
+//   - cli,from should be \d+ (eg 31676012321)
+//   - to is either [0-9*]+ for a (partially shielded/) phonenumber, or .+ for APN or Voicemail, or the likes
+//   - account is free text (non-empty)
+//   - usage is an integer >= 0
+//   - costs is a float with four decimal digits. We strip the dot and interpret it as an integer, to avoid weird rounding errors during processing
+//   - source,destination are free text, but typically either empty or take the form "word(s) - word(s) - word(s)"
+//   - leg is an integer >= 1
+//   - reason is in {ORIG,CFIM,CFOR,CFNA,CFBS,ROAM,PBXOR}, but there might be other ones
+//   - package is free text (or empty)
+//   - {package,network,service}_costs are either empty or conform to the "costs" column
+
+// FieldsPerLine are the expected number of fields in each CSV line.
+const FieldsPerLine = 17
+
+// ImportIndex keeps track of what column corresponds to what data.
+type ImportIndex int
+
+// These are our numbered input fields
+const (
+	ImportUnknown ImportIndex = iota
+	ImportCid
+	ImportTime
+	ImportType
+	ImportCLI
+	ImportFrom
+	ImportTo
+	ImportAccount
+	ImportUsage
+	ImportCosts
+	ImportSource
+	ImportDestination
+	ImportLeg
+	ImportReason
+	ImportPackage
+	ImportPackageCosts
+	ImportNetworkCosts
+	ImportServiceCosts
+)
diff --git a/record.go b/record.go
index 2aaa342..603a245 100644
--- a/record.go
+++ b/record.go
@@ -41,7 +41,7 @@ const (
 	PBXOR
 )
 
-// Line contains common metadata for a record
+// Line contains the original metadata of a (call) detail record
 type Line struct {
 	Id          string
 	Time        time.Time
@@ -51,9 +51,17 @@ type Line struct {
 	Account     string
 	Source      string
 	Destination string
-	Reason      ReasonKind
+	RawCount    int
+	RawCosts    int
 	Leg         int
+	Reason      ReasonKind
 	Kind        LineKind
+
+	// non-public properties
+	pkg          string
+	package_cost int
+	network_cost int
+	service_cost int
 }
 
 // PricedLine connects a cost (buy) and price (sell) to a particular Line
@@ -68,7 +76,7 @@ type PricedLine struct {
 type Call struct {
 	From     string
 	To       string
-	Duration int
+	Duration time.Duration
 	Cost     int
 	Price    int
 	Legs     []PricedLine