Slides

S1: Meeting 10

Administrative Issues
- Final Exam. : Syllabus, Format
- Last call for grade verification
Today's Topics for Discussion
- Year 2000 Issue in Software Industry
  - What are the Problems?
  - How vast are the Problems?
  - What are the soluitions?
  - MSG Case Study
- Component Models
  - Video Tape
  - Discussion Questions

S2: Year 2000 Issue in Software Industry

S3: A Case Study: Insurance Industry

Problems
- Computing customer age in year 2000
  - Customer born in 1926 = > (00 -26) = -26
- Annuity Eligibilty (age > 60):
  - Make every one ineligible
- Sorting records:
  - "00" shows up oldest record instead of newest
- Discard old data (migrate to archive)
  - May discard newest data
- Areas of Impact
- Service: Custoers will be affected.
- Product Value: potential loss of customers
Risks
- Premium payment computation, under/over billing
- Premature expiry dates on policies
- Determining age based risks
- System recovery, COTS packages

S4: What are the Problems?

Year as a Two digit number
- Arithmetic, e.g. negative age
- Comparison, Sorting
- Input, Output to Databases and Files
Leap recognition algorithms
- divisible(Y, 4) {unless divisible(Y, 100) {unless divisible(Y, 400)}}
- Year 2000 is a leap year, Year 2100 is not!
Magic Number
- YY = "99" or "00" = > never delete this or demo
System date data type overflow
- Ex. 2034-09-30 for Unix time function

S5: How vast are the Problems? Compliance Questions

Are there any date fields used by the product?
How many digits are the year fields?
Does it accept dates directly from the user?
How does the user specify the year?
How does product compute leap year?
Are dates stored internally as a specific "date" data type?
- Is it done using a base year with an offset number of seconds/days?
- What size is the data type storing the offset?
What is the valid date range?
Are two-digit years allowed?
- If so, how are they usd in comparison, calculations, etc?
Are any special values for date fields used? (e.g. 9/9/99, 1/1/11)
Does product use dates in verifying license validity?
Details of solution approach. ...

S6: How vast are the Problems?

System Software
- O.S.: Expiry of trial software/ Passwords/ Data cache
- DBMS: Date storage, Date/Time Arithmetic
- Mathematical software: random number generators
- Compilers: Time-stamped object codes (e.g. makefiles)
Embedded Systems
- Medical: Pacemaker, Heart defribulators
- Instrumentation: Power generation, Water, Factory
- Monitoring: Heating, A/C, Security, Air/Water quality
- Communication: Telephone exchanges, Satellites,
- Finance: ATMs, Credit cards, smart Id cards
- Other: TV, VCR, Microwave, Fax, ...
Personal Computer
- Real Time Clock
- Basic Input/Output System (BIOS)
- Operating System or Application Software
Paranoid
- Power: Best selling chrismas 1999 gift = batteries ?
- Bank Account: Save you Dec 1999 statements!
- Will any airplanes fly that night?
- University: Graduate before 2000 ? Get your transcripts?

S7: What are the solutions?

Leap year, magic number and date counter overflow problems
- Fix as they are found
Approaches to Two digit year problem
- Expand year field to 4 digits
- Encode century information in a six digit space
- Use a 100 year logic window
- Data bridge with a logic window
- Reverse system clock with 28 year bridge
- Replace or retire the system
- Do nothing to software
Comparison:
- Expansion: +general solution for future, but costly
- Encoding: + preserves data length, but costly
- Logic: + less changes but limits to 100 year window

S8: Testing for Y2K Compliance

S9: Component Models

S10: Component Models - References